Accumulated Amortization of Deferred Finance Costs and Other Assets Represents the amount of accumulated amortization of deferred financing costs and other assets on the reporting date by the entity. Deferred financing costs, accumulated amortization (in dollars) Deferred financing costs, accumulated amortization Accrete convertible preferred units to redemption amount Represents the accretion of preferred units to redemption amount. Accrete of Preferred Units to Redemption Cash Paid for [Abstract] Cash paid for: Aggregate par or stated value of issued common units. Common Units Common units, 100,000,000 units authorized; zero issued at December 31, 2012 and 2011, respectively The authorized number of common units permitted to be issued by an entity's charter and bylaws. Common Units Authorized Common units, units authorized Common units, authorized (in shares) Common Units Issued Total number of common units of an entity that have been sold or granted to owners (includes common units that were issued, repurchased and remain in the treasury). These units represent capital invested by the firm's owners, and may be all or only a portion of the number of units authorized. Units issued include units outstanding and shares held in the treasury. Common units, units issued Award Type [Axis] Deemed Payment and Termination of Notes Receivable Deemed payment and termination of notes receivable The amount of deemed payment and termination of notes receivable in noncash investing or financing transactions. Document and Entity Information Joint Interest Billings Debt Instrument Additional Interest Expense Effective Interest Interest expense in excess of interest currently payable Represents the additional interest expense recognized using the effective interest method. Amendment Description Jubilee Field Unitization Amendment Flag Jubilee Field Unitization Disclosure [Text Block] Jubilee Field Unitization Entire disclosure on the Jubilee Field Unitization. Aging of capitalized exploratory well costs and number of projects for which exploratory well costs were capitalized for more than one year Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year [Abstract] Notes receivable applied to FPSO purchase Notes Receivable Applied The amount of notes receivable applied in noncash investing activities. Acquisition of FPSO Joint Interest Billings Oil and Gas Joint Interest Billing Receivable Disclosure [Text Block] Represents all disclosure related to joint interest billings in one text block. Relinquishments of profit units (in shares) Stock Issued During Period Shares Share Based Compensation Forfeited and Cancelled Number of shares (or other type of equity) forfeited and cancelled during the period. Payments to Acquire Oil and Gas Assets Acquisition of oil and gas assets The cash outflow for acquisition of oil and gas assets during the reporting period. All Countries [Domain] Significant Acquisitions and Disposals Cost of Acquired Assets Cash Paid Amount of cash paid to acquire the asset. Cash paid for purchase Common Units [Member] Common units Represent the common units of the entity. Voting Rights Per Common Share Voting rights per common share Represents the number of voting rights per each common share held. Acquisition of FPSO Acquisition of FPSO Disclosure [Text Block] The entire disclosure for acquisition of FPSO. It also includes the disclosure for notes receivable applied to the purchase price. Estimates of Proved Oil and Natural Gas Reserve [Policy Text Block] Estimates of Proved Oil and Natural Gas Reserves Disclosure of accounting policy for estimates of proved oil and natural gas reserves. Expected construction period for capitalization of interest costs on major projects The expected period of time estimated for a major construction project to qualify for capitalization of interest. Major Projects Construction Period for Capitalization of Interest Restricted Cash, Required Period for Contractual Future Payments Restricted cash period required as per commercial debt facility to meet interest and commitment fee payments Period of time used to determine level of contractually required restricted cash balances. Office Furniture Fixtures and Computer Equipment [Member] Office furniture, fixtures and computer equipment Represents the equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities and the long lived, depreciable assets that are used in the creation, maintenance and utilization of information systems. Capitalized Interest [Abstract] Capitalized Interest Capitalized Exploratory Well Cost Expensed in Same Period Capitalized exploratory well costs subsequently expensed in the same period Represents the capitalized exploratory well costs that were subsequently expensed in the same period. Current Fiscal Year End Date Submission of Plan of Development to Ministry of Energy Period Submission of PoD to Ghana's Ministry of Energy, period Represents the period taken, after a declaration of commerciality, if any, in which a plan of development would be prepared and submitted to Ministry of Energy. BERMUDA Bermuda Period of Negotiation and Consultation of Notice of Dispute Given to Ministry of Energy Period of negotiation and consultation of notice of dispute issued to Ministry of Energy by the entity Represents the period of negotiation and consultation of notice of dispute issued to Ministry of Energy that can be extended if mutually agreed upon. Teak 1 Discovery [Member] Teak-1 Discovery Represents information pertaining to the Teak-1 Discovery. Teak 2 Discovery [Member] Teak-2 Discovery Represents information pertaining to the Teak-2 Discovery. Mahogany East Area [Member] Mahogany East Area Represents information pertaining to the Mahogany east area. Accrued Exploration Development and Production Costs, Current Accrued exploration, development and production Carrying value as of the balance sheet date of exploration, development and production costs that are incurred and payable. It is used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued General and Administrative Expenses, Current Accrued general and administrative expenses Carrying value as of the balance sheet date of expenses of managing and administering the affairs of the entity that are incurred and payable. It is used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Floating Production Storage and Offloading Vessel [Member] FPSO Represents the details pertaining to the floating production, storage and offloading vessel (FPSO). Tullow [Member] Tullow Represents Tullow Ghana Limited, a subsidiary of Tullow Oil plc, unit operator of the Jubilee Field. Significant Acquisitions and Disposals Cost of Acquired Asset, Other Noncash Consideration Fair value of noncash consideration given by the acquirer to acquire the asset. Does not include cash paid, the fair value of debt and securities issued and liabilities incurred to acquire the asset. Notes receivable applied to FPSO purchase Jubilee Field Jubilee Field [Member] Represents details pertaining to the Jubilee Field. Document Period End Date Jubilee Unitization and Unit Operating Agreement [Member] Represents details pertaining to the Jubilee Unitization and Unit Operating Agreement (Jubilee UUOA). Jubilee UUOA WCTP Block West Cape Three Points Block [Member] Represents details pertaining to the West Cape Three Points Block (WCTP). West Cape Three Points Block Petroleum Agreements [Member] Represents details pertaining to the West Cape Three Points petroleum agreements. WCTP PA DT Block Deepwater Tano Block [Member] Represents details pertaining to the Deepwater Tano Block (DT). Ghana National Petroleum Corporation [Member] GNPC Represents the Ghana National Petroleum Corporation, a unit partner of an entity. EO Group [Member] EO Group Represents the EO Group Limited, a unit partner of an entity. Oil and Gas Joint Interest Billing Receivables [Line Items] Joint interest billings Initial Tract Participation Percentage Per Block Initial tract participation for each block (as a percent) Represents the initial percentage of tract participation for each block under operating agreement. Percentage of Participation Interest Required to Call for Second Redetermination Percentage participation interest required to call for second redetermination Represents the percentage of participation interest of a party under the unitization and unit operating agreement who may call for a second redetermination. Entity [Domain] Redetermination Tract Participation Percentage Per Block Tract participation for each block after redetermination (as a percent) Represents the percentage of tract participation for each block under operating agreement retroactively applied after redetermination process. Unit Interest Percentage as Previously Held Unit interest as previously held (as a percent) Represents the percentage of unit interest as previously held by the entity immediately before the date when additional interest is acquired by the unit operator. Unit Interest Percentage after Redetermination Unit interest after redetermination process (as a percent) Represents the percentage of unit interest, retroactively applied, held by the entity after redetermination process under the terms of a operating agreement. Participation Interest Change Increase in Joint Interest Billing Receivables after Redetermination Process Increase in joint interest billing receivables due to change in participation interest as a result of redetermination process Represents the amount of increase in joint interest billing receivables due to change in participation interest related to redetermination process. Participation Interest Change Increase in Oil and Gas Properties after Redetermination Process Increases in oil and gas properties due to change in participation interest resulting from redetermination process Represents the amount of increase in oil and gas properties due to change in participation interest as a result of redetermination process. Participation Interest Change Increase in Notes Receivable after Redetermination Process Increases in notes receivable due to change in participation interest resulting from redetermination process Represents the amount of increase in notes receivable due to change in participation interest as a result of the redetermination process. Increases in inventories due to change in participation interest resulting from redetermination process Represents the amount of increase in inventories due to change in participation interest as a result of the redetermination process. Participation Interest Change Increase in Inventories after Redetermination Process Participation Interest Change Increase in Oil and Gas Production Expenses after Redetermination Process Increases in oil and gas production expenses due to change in participation interest from redetermination process Represents the amount of increase in oil and gas production expenses due to change in participation interest as a result of the redetermination process. Participation Interest Change Increase in General and Administrative Expenses after Redetermination Process Increases in general and administrative expenses due to change in participation interest from redetermination process Represents the amount of increase in general and administrative expenses due to change in participation interest as a result of the redetermination process. Increases in accounts payable due to change in participation interest from redetermination process Represents the amount of increase in accounts payable due to change in participation interest as a result of the redetermination process. Participation Interest Change Increase in Accounts Payable after Redetermination Process Oil and Gas Joint Interest Billing Receivables [Table] Schedule of net carrying value as of the Balance Sheet date of accounts receivable attributable to joint interest partners in oil and gas properties. Also includes details pertaining to the information regarding the unit holders. Represents the percentage of contractual working interest acquired from one unit partner by another unit partner. Acquired Working Interest Percentage Working interest acquired in EO Group (as a percent) Represents the increase in percentage of participation interest during the period due to the acquisition by the Unit Operator of another unit partner's interest. Participation Interest Percentage Increase Increase in the participation interest in the Jubilee Unit (as a percent) GNPC's paying interest (as a percent) Represents percentage of paying interest during the period. Paying Interest, Percentage Working Interest Percentage Working interest (as a percent) Represents the percentage of investment in oil and gas operations in which an entity is directly liable for a portion of the ongoing costs associated with exploration and appraisal activities. Divestiture Oil and Gas Properties Working Interest Assigned Represents percentage of working interest assigned (subject to government approval) in an oil and gas property. Working interest assigned to Chevron (as a percent) Oil and Gas Discoveries [Axis] Represents the details pertaining to various oil and gas discoveries wherein exploratory activities are carried out. Oil and Gas Operating Agreements [Axis] Represents the activity related to oil and gas operating agreements. Oil and Gas Blocks [Axis] Represents activity related to various oil and gas blocks. Oil and Gas Discoveries[Domain] Represents the names of various oil and gas discoveries wherein exploratory activities are carried out. Oil and Gas Blocks [Domain] Represents the activity by individual oil and gas blocks. Oil and Gas Operating Agreements [Domain] Represents activity by specific oil and gas operating agreements. Derivative Contract Term [Axis] Represents the grouping of derivative contract terms. Derivative Contract Term [Domain] This element represents individual derivative contract terms. Term January 2013 to December 2013 [Member] Term January 2013 to December 2013 Represents the derivative contracts with a term from January 2013 to December 2013. Term October 2012 to December 2012 [Member] Term October 2012 to December 2012 Represents the derivative contracts with a term from July 2012 to December 2012. Term August 2012 to December 2012 [Member] Term August 2012 to December 2012 Represents the derivative contracts with a term from August 2012 to December 2012. Derivative Weighted Average Deferred Premium Per Barrel Weighted average deferred premium per Bbl Represents the weighted average deferred premium per barrel of the derivative contracts expressed in dollars per barrel. Preferred return per annum for first nine years (as a percent) Represents the preferred return amount per unit of the accreted value per annum, compounded quarterly, for the first nine years after the year of the Kosmos Energy Holdings' initial operating agreement. Percentage of Accreted Value for First Nine Years Preferred return per annum after first nine years (as a percent) Represents the preferred return amount per unit of the accredited value per annum, compounded quarterly, after the first nine years of the Kosmos Energy Holdings' initial operating agreement. Percentage of Accreted Value after Nine Years Noble Energy EG Ltd [Member] Noble Represents the party to an offshore drilling contract. Initial rig rate per day Represents the initial rig rate per day under an offshore drilling contract entered into by the entity. Offshore Drilling Initial Rig Rate, Per Day Offshore Drilling Adjusted Rig Rate, Per Day Adjusted rig rate per day Represents the adjusted rig rate per day under an offshore drilling contract entered into by the entity. Drilling contract period (in days) Represents the period of offshore drilling contract entered into by the entity. Offshore Drilling Contract Period Offshore Drilling Contract Allotted Period Drilling contract allotted period (in days) Represents the allotted period of offshore drilling contract to the entity. GHANA Ghana Profit Units [Member] Represents the details pertaining to common units designated as profit units issued by the entity. Profit units Long Term Incentive Plan [Member] Represents the details pertaining to Long-Term Incentive Plan, which provides for the granting of incentive awards. LTIP Schedule of Share Based Compensation Stock Awards Available for Issuance [Table Text Block] Schedule of number of shares available for issuance pursuant to awards Tabular disclosure of share-based compensation plans that may be presented in a table for awards available for future grant. The information that may be disclosed in this table may include, but not limited to, number of approved and authorized awards, number of awards issued and forfeited. Share Based Compensation Arrangement by Share Based Payment Award Threshold Value Threshold value to employees, management and directors (in dollars per units) Represents the threshold value of an award for employees, management and directors for profit units. Vesting Rights Percentage as of Date of Issuance Vesting rights as of the date of issuance (as a percent) Description of award terms as to how many shares or portion of an award as of the date of issuance are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, shown as a percentage. Vesting Rights Percentage on Anniversary Date for Each of Next Four Years Description of award terms as to how many shares or portion of an award as on the anniversary date for each of the next four years are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, shown as a percentage. Additional vesting rights on the anniversary date for each of the next four years (as a percent) Vesting Rights Percentage on Second and Fourth Anniversary of Issuance Date Description of award terms as to how many shares or portion of an award as on the second and fourth anniversary of issuance date are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, shown as a percentage. Vesting rights on the second and fourth anniversary of issuance date (as a percent) Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options Weighted Average Grant Date Fair Value [Roll Forward] Weighted-Average Grant-Date Fair Value for awards Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options Weighted Average Grant Date Fair Value Represents the weighted average grant date fair value of equity-based award plans other than stock (unit) option plans outstanding as of the balance sheet date. Outstanding at beginning of the period (in dollars per share) Outstanding at the end of the period (in dollars per share) Accounting Policies Represents the number of equity-based payment instruments, excluding stock (or unit) options which were exchanged during the reporting period. Exchanged (in shares) Unvested profit units exchanged for service vesting restricted stock awards (in shares) Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other than Options Exchange in Period Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions Projected Turnover Rate Projected turnover rate (as a percent) Represents the projected turnover rate assumption that is used in valuing an share-based award. Entity Well-known Seasoned Issuer Share Based Compensation Arrangement by Share Based Payment Award Number of Shares Available For Grant [Abstract] Number of shares available for future grant Entity Voluntary Filers Income Taxes [Table] Disclosures pertaining to income taxes. Entity Current Reporting Status Geopolitical areas recognized by governments of the world as grouping of countries. All Countries [Axis] Entity Filer Category Other Foreign Countries [Member] Represents the foreign countries other than United States. Foreign-other Entity Public Float Income Taxes [Line Items] Income Taxes Entity Registrant Name Stock Issued During Period Share Based Compensation Cancelled Threshold Amount The threshold value of the common units that were cancelled as part of a corporate reorganization. Threshold value of awards cancelled (in dollars per unit) Entity Central Index Key Offshore Drilling Contract Commitments [Member] Represents the commitments under offshore drilling contract. Offshore drilling contract commitments Line of Credit Facility Contingent Increase to Maximum Borrowing Capacity Increased maximum borrowing capacity under the credit facility if any one or more of the existing banks or new banks agree to provide such increased commitment amount. Maximum increased borrowing capacity Restricted Cash and Cash Equivalents, Type of Restriction [Axis] Information by type or source of restriction on available cash. Restricted Cash and Cash Equivalents, Type of Restriction [Domain] Type or source of restriction on available cash. Entity Common Stock, Shares Outstanding Gain (Loss) on Commodity Derivative Instruments, Net Pretax Aggregate net gain (loss) on commodity derivative instruments recognized in earnings during the period, before tax effects. Derivatives, net Derivative Financial Instruments Liabilities Fair Value Nonperformance Risk Impact Decrease in fair value of derivative liabilities attributable to nonperformance risk The amount of the reduction in the derivative instrument liability related to nonperformance risk as of the balance sheet date Capitalized exploratory well costs charged to expense Represents the capitalized exploratory well costs charged to expense exclusive of costs capitalized and expensed in the same period. Capitalized Exploratory Well Cost Charged to Expense Excluding Costs Capitalized and Expensed in Same Period Founding Management and Directors [Member] Persons responsible in establishing and organizing the company. Founding Management and Directors Employees [Member] Employees Persons working for the entity. Accrued taxes other than income Accrual for All Other Taxes Current Carrying value as of the balance sheet date of obligations incurred and payable for taxes other than income taxes. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Line of Credit Facility Available Capacity Commitment Fees Percentage The commitment fees, expressed as a percentage of the then-applicable respective margin, for available but unused credit capacity under the credit facility. Commitment fee percentage of the then-applicable margin when commitment is available for utilization Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accounts Payable and Accrued Liabilities Line of Credit Facility Revolving Credit Conversion to Term Loan [Member] Represents activity related to a facility that converts from a revolver to a term loan. Facility Commercial Debt Facility Commitment fees Represents the charge against earnings during the period for commitment fees. Debt Related Commitment Fees Threeway Collars [Member] Three-way Collars Represents a three-way collar derivative contract which establishes a floor, swap and ceiling strike price. Three-way collar contracts indexed to Dated Brent prices Money Market Accounts Excluded Amount of money market accounts excluded from fair value measurements, as reported in our annual report on Form 10-K Represents the amount of money market accounts excluded from fair value measurements, as reported in our annual report on Form 10-K. Stock Issued During Period Shares, New Issues over Allotment Option Number of new stock issued during the period pursuant to the over-allotment option exercised by the underwriters. Shares issued pursuant to over-allotment option Odum Discovery [Member] Odum Discovery Represents information pertaining to the Odum discovery. Akasa Discovery [Member] Akasa Discovery Represents information pertaining to the Akasa discovery. Term January 2014 to December 2014 [Member] Term January 2014 to December 2014 Represents the derivative contracts with a term from January 2014 to December 2014. Term January 2015 to December 2015 [Member] Term January 2015 to December 2015 Represents the derivative contracts with a term from January 2015 to December 2015. Term January 2016 to June 2016 [Member] Term January 2016 to June 2016 Represents the derivative contracts with a term from January 2016 to June 2016. Document Fiscal Year Focus Cash Settlements Made Included in Derivative Liabilities Current Cash settlements made on purchased puts and swaps with calls which were settled in the month subsequent to period end Represents the amount of cash settlements made included in current derivative liabilities. Document Fiscal Period Focus Treasury Stock [Policy Text Block] Treasury Stock Disclosure of accounting policy for treasury stock. Essaouira Offshore Block [Member] Essaouira Offshore Block Represents the information pertaining to Essaouira Offshore Block, located offshore Morocco. Canamens Energy Morocco SARL [Member] Canamens Represents the information pertaining to Canamens Energy Morocco SARL. Restricted Stock Awards and Restricted Stock Units Restricted Stock Awards and Restricted Stock Units RSU [Member] Represents information pertaining to the restricted stock awards and restricted stock units (RSUs) as awarded by the entity to their employees as a form of incentive compensation. Service Vesting Restricted Stock Awards Represents information pertaining to the restricted stock awards with service vesting criteria. Service Vesting Restricted Stock Awards [Member] Market/Service Vesting Restricted Stock Awards Represents information pertaining to the restricted stock awards with market and service vesting criteria. Market and Service Vesting Restricted Stock Awards [Member] Service Vesting Restricted Stock Units Represents information pertaining to the restricted stock units with service vesting criteria. Service Vesting Restricted Stock Units [Member] Market/Service Vesting Restricted Stock Units Represents information pertaining to the restricted stock units with market and service vesting criteria. Market and Service Vesting Restricted Stock Units [Member] Accounts payable to subsidiaries Accounts Payable, Related Parties, Current Share Based Compensation Arrangement by Share Based Payment Award, Award Vesting Percentage Vesting percentage of the awards granted Represents the percentage the granted awards can potentially vest up to. Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options Relinquished in Period Weighted Average Grant Date, Fair Value Represents the weighted average grant date fair value of equity-based payment instruments, excluding stock (or unit) options which were relinquished during the reporting period. Relinquished (in dollars per share) Correction of Error Amount Capitalized Previously Recorded as Exploration Expense [Member] Correction of immaterial error Represents the capitalization which was previously recorded as exploration expense. Legal Entity [Axis] Derivative, Deferred Premium, Current Deferred premiums related to commodity derivative contracts Represents the amount of deferred premiums of the derivative contracts included in current derivative liabilities. Document Type Represents the amount of deferred premiums of the derivative contracts (namely puts and compound options) included in current derivative liabilities. Derivative Deferred Premium Current Related to Purchased Puts and Compound Options Deferred premiums related to purchased puts and compound options contracts Derivative Deferred Premium Current Related to Purchased Puts Deferred premiums related to purchased puts Represents the amount of deferred premiums of the derivative contracts (namely purchased puts) included in current derivative liabilities. Derivative, Deferred Premium, Non Current Deferred premiums related to commodity derivative contracts Represents the amount of deferred premiums of the derivative contracts included in non-current derivative liabilities. Debt Instrument, Covenant Net Debt to EBITDAX Ratio Net debt to EBITDAX ratio Represents the ratio of net debt to EBITDAX (earnings before interest, taxes, depreciation, amortization and exploration expenses) permitted under financial covenants. Accounts Receivable, Net, Current Oil sales Debt Instrument, Covenant EBITDAX to Interest Payable Ratio EBITDAX to interest payable ratio Represents the ratio of EBITDAX (earnings before interest, taxes, depreciation, amortization and exploration expenses) to interest payable permitted under financial covenants. Threeway Collars 1 [Member] Three-way collars Represents the second three-way collar derivative contract which establishes a floor, swap and a ceiling strike price. Ndian River Block [Member] Ndian River Block Represents information pertaining to Ndian River Block, located onshore Cameroon. Depletion costs included in crude oil inventory and other receivables Amount of asset recognized due to an underlift position in oil and gas producing activities. Underlift Asset in Oil and Gas Line of Credit Cancelled Uncommitted Borrowing Capacity Cancellation of the uncommitted borrowing capicity The amount of cancelled uncommitted borrowing capacity under the credit facility. Morocco MOROCCO Swap with Calls [Member] A forward-based contract in which two parties agree to swap streams of payments over a specified period and with call option. The payment streams are based on an agreed-upon (or notional) principal amount. The term notional is used because swap contracts generally involve no exchange of principal at either inception or maturity. Rather, the notional amount serves as a basis for calculation of the payment streams to be exchanged. Swaps with calls Represents the amount of cash settlements on derivatives. Cash settlements on derivatives Cash Settlements on Derivatives Line of Credit Facility, Increase in Remaining Borrowing Capacity Increase in undrawn availability Represents the increase in availability under the credit facility after the normal borrowing base determination. Block 42 and Block 45 [Member] Block 42 and Block 45 Represents information pertaining to Block 42 and Block 45, located offshore Suriname. Chevron Represents information pertaining to Chevron Global Energy Inc. (Chevron). Chevron Global Energy Inc [Member] Schedule of Organization [Line Items] Organization Provisional Pricing Average Subject to Final Pricing Average price, subject to final pricing Average price, subject to final pricing. Stock Issued During Period Shares New Issues Excluding Shares over Allotment Option Common shares issued excluding shares issued pursuant to over-allotment option Number of new stock issued during the period excluding stock issued pursuant to the over-allotment option exercised by the underwriters. Defined Contribution Plan Employer Matching Contribution as Percentage of Employee Contribution Company's matching contribution as percentage of employee contribution Represents the employer's matching contribution to the defined benefit plan as percentage of employee contribution. Stock Issued During Period Shares Public Issue Common shares issued under IPO Represents the number of shares of public stock issued during the period. Long Term Debt, Future Minimum Interest Payments Due [Abstract] Interest payments on long-term debt Total Amount of required minimum interest payments for debt having initial maturities beyond one year or beyond the normal operating cycle, if longer. Long Term Debt, Future Minimum Interest Payments, Due Long Term Debt, Future Minimum Interest Payments Due, Current 2013 Amount of required minimum interest payments maturing in the next fiscal year following the latest fiscal year for debt having initial maturities beyond one year or beyond the normal operating cycle, if longer. Long Term Debt, Future Minimum Interest Payments Due in Year Two 2014 Amount of required minimum interest payments maturing in the second fiscal year following the latest fiscal year for debt having initial maturities beyond one year or beyond the normal operating cycle, if longer. 2015 Amount of required minimum interest payments maturing in the third fiscal year following the latest fiscal year for debt having initial maturities beyond one year or beyond the normal operating cycle, if longer. Long Term Debt, Future Minimum Interest Payments Due in Year Three Long Term Debt, Future Minimum Interest Payments Due in Year Four 2016 Amount of required minimum interest payments maturing in the fourth fiscal year following the latest fiscal year for debt having initial maturities beyond one year or beyond the normal operating cycle, if longer. Amount of required minimum interest payments maturing in the fifth fiscal year following the latest fiscal year for debt having initial maturities beyond one year or beyond the normal operating cycle, if longer. Long Term Debt, Future Minimum Interest Payments Due in Year Five 2017 Thereafter Amount of required minimum interest payments maturing after the fifth fiscal year following the latest fiscal year for debt having initial maturities beyond one year or beyond the normal operating cycle, if longer. Long Term Debt, Future Minimum Interest Payments Due after Year Five Commitments for exploration activities under pertoleum contracts Represents the amount of commitments related to exploration activities under petroleum contracts. Commitments for Exploration Activities under Pertoleum Contracts Accounts Payable, Current Accounts payable Schedule of reconciliation of the differences between applicable statutory tax rate and effective income tax rate Tabular disclosure of the reconciliation using percentage of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations. Schedule of Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Table Text Block] Deferred Tax Assets, Foreign Capitalized Operating Expenses Ghana foreign capitalized operating expenses Amount of deferred tax liability attributable to taxable temporary differences from foreign capitalized operating expenses. Cameroon, Morocco, Suriname and Mauritania Represents information pertaining to Cameroon, Morocco, Suriname and Mauritania. Cameroon Morocco Suriname and Mauritania [Member] Period for which Entity is No Longer in Cumulative Loss Position Period for which entity is no longer in cumulative loss position Represents the period for which the entity is no longer in cumulative loss position. Operating Loss Carryforwards Expected to be Utilized Amount of net operating loss carryforward expected to be utilized Represents the amount of net operating loss carryforward expected to be utilized during the current fiscal year. Income Tax Holiday Income Tax Rate Tax rate applicable relating to tax holiday (as a percent) Represents the effect of tax rate of the aggregate dollar amount of the income tax benefit resulting from the income tax holidays granted to the entity by taxing jurisdictions. Income Tax Holiday Period from Date of First Production Period of income tax holiday from date of first production Represents the period of income tax holiday from the date of first production. Operating Loss Carryforwards Foreign Subject to Expiration Foreign net operating loss carryforwards which begin to expire in 2012 Amount attributable to deductible foreign operating loss carryforwards that are subject to expiration dates. Amount attributable to deductible foreign operating loss carryforwards that are not subject to expiration dates. Operating Loss Carryforwards Foreign Not Subject to Expiration Foreign net operating loss carryforwards which do not expire Line of Credit Facility Amount of Reduction in Borrowing Capacity Amount of commitments cancelled Represents the amount of reduction in borrowing capacity under the credit facility. Debt Instrument Covenant Interest Coverage Ratio Interest cover ratio Represents interest coverage ratio required to be maintained under the terms of the debt covenants. Threeway Collars 2 [Member] Three-way collars Represents the third three-way collar derivative contract which establishes a floor, swap and a ceiling strike price. Equity in (earnings) losses of subsidiaries Represents the entity's proportionate share for the period of the net income (loss) of its consolidated subsidiaries to which the equity method of accounting is applied. Income (Loss) from Equity Method Investments in Consolidated Subsidiaries Increase (Decrease) in Due from to Related Parties (Increase) decrease due to/from related party The increase (decrease) during the reporting period in the aggregate amount of obligations due from or to be paid to the following types of related parties: a parent company and its subsidiaries; subsidiaries of a common parent; an entity and trust for the benefit of employees, such as pension and profit-sharing trusts that are managed by or under the trusteeship of the entities' management; an entity and its principal owners, management, or member of their immediate families; affiliates; or other parties with the ability to exert significant influence. Schedule of Income Tax Provision By Jurisdiction [Table Text Block] Tabular disclosure of current and deferred provision for income taxes by jurisdictions. Schedule of components of the provision for income taxes attributable to our income (loss) before income taxes The number of shares (or other type of equity) awarded to grantees and subsequently forfeited and added to the number of awards available for distribution. Awards forfeited (in shares) Share Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Shares Forfeited And Added in Period Threeway Collars 3 [Member] Three-way collars Represents the fourth three-way collar derivative contract, which establishes a floor, swap and a ceiling strike price. Granted (in dollars per share) Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other Than Options Granted Weighted Average Grant Date Fair Value Represents the weighted average grant date fair value of equity-based payment instruments, excluding stock (or unit) options, which were granted during the reporting period. Line of Credit Facility Term Availability period for the credit facility Represents the term for which amount is allowed to be borrowed under the credit facility. Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other than Options Exchanged in Period Weighted Average Grant Date Fair Value Exchanged (in dollars per share) Represents the weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were exchanged during the reporting period. Property, Plant and Equipment Schedule of Estimated Lives [Table Text Block] Schedule of estimated useful lives of other property Tabular disclosure of the useful life of physical assets that are used in the normal conduct of business to produce goods and services and not intended for sale. Reimbursement of previously incurred expenses Represents the proceeds received from divesture of an oil and gas property . Reimbursement Proceeds from Divestiture Oil and Gas Properties Line of Credit Facility Unavailable Capacity Commitment Fee Percentage Commitment fee percentage of the then-applicable margin when commitment is not available for utilization The commitment fees, expressed as a percentage of the ten-applicable respective margin, for unavailable credit capacity under the credit facility Standardized Measure Price Per Barrel Price per barrel of crude oil (in dollars per bbl) Represents the price per barrel used in the calculation of the standardized measure of oil and gas. Number of Classes of Common Stock Issued and Outstanding Number of classes of common stock Represents the number of classes of common stock issued and outstanding as of the balance sheet date. Net Income (Loss) Available to Common Stockholders Basic and Diluted [Abstract] Net income (loss) per share attributable to common shareholders: Increase (Decrease) in Exploration Expense Represents the increase (decrease) in exploration costs incurred during the reporting period. Reduction in exploration expense Increase (Decrease) in General and Administrative Expense Represents the increase (decrease) in general and administrative expense incurred during the reporting period. Reduction in general and administrative expense Accrued Liabilities, Current [Abstract] Accrued liabilities: UNITED STATES United States Accrued Income Taxes, Current Income taxes Accrued liabilities Accrued Liabilities, Current Accrued liabilities Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Loss) [Member] AOCI Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax Accumulated other comprehensive income Additional Paid in Capital, Common Stock Additional paid-in capital Treasury stock, at cost, 649,818 and zero shares at December 31, 2011 and 2010, Additional Paid-in Capital Additional Paid-in Capital [Member] Amortization Amortization Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Equity-based compensation Compensation expense recognized Allocated Share-based Compensation Expense Compensation expense recognized Allowance for Doubtful Accounts Receivable, Recoveries Doubtful accounts expense Reversal of valuation allowance for long-term joint interest billing receivables related to Jubilee Field development costs Allowance for doubtful receivables Allowance for Trade Receivables [Member] Long-term receivables - joint interest billings, allowance (in dollars) Allowance for Doubtful Accounts Receivable, Noncurrent Amortization of Financing Costs Amortization-deferred financing costs Dilutive Securities, Effect on Basic Earnings Per Share, Including Options and Restrictive Stock Units Diluted adjustments to income allocable to participating securities Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Outstanding restricted stock awards and restricted stock units excluded from the computations of diluted net income (loss) per share (in shares) Asset Retirement Obligation, Accretion Expense Accretion expense Asset Retirement Obligations Asset Retirement Obligations, Noncurrent Asset retirement obligations Beginning asset retirement obligations Ending asset retirement obligations Asset Retirement Obligation, Liabilities Incurred Liabilities incurred during period Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset retirement obligations: Asset Retirement Obligation, Liabilities Settled Liabilities settled during period Asset Retirement Obligation Disclosure [Text Block] Asset Retirement Obligations Asset Retirement Obligation, Revision of Estimate Revisions in estimated retirement obligations Asset Retirement Obligations Asset Retirement Obligations and Environmental Cost, Policy [Policy Text Block] Assets, Net Total fair value, net Current assets: Assets, Current [Abstract] Assets Assets [Abstract] Assets, Current Total current assets Assets Total assets Assets, Fair Value Disclosure [Abstract] Assets: Basic Earnings Per Share, Pro Forma Pro forma basic (in dollars per share) General Basis of Accounting, Policy [Policy Text Block] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Capitalized Exploratory Well Costs, Roll Forward [Table Text Block] Schedule of capitalized exploratory well costs Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves Additions to capitalized exploratory well costs pending the determination of proved reserves Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year Exploratory well costs capitalized for a period one to three years Capitalized Costs, Support Equipment and Facilities Support equipment and facilities Capitalized Exploratory Well Costs Balance at the beginning of the period Balance at the end of the period Ending balance Capitalized Interest Costs [Member] Capitalized interest Capitalized Exploratory Well Costs that Have Been Capitalized for Period of One Year or Less Exploratory well costs capitalized for a period of one year or less Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Gains expected to be reclassified from AOCI to interest expense Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Restricted Cash Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents Restricted Cash Cash and Cash Equivalents [Member] Cash Flow Hedging [Member] Derivatives in cash flow hedging relationships Chief Executive Officer [Member] Retired Chairman and Chief Executive Officer Class of Stock [Domain] Variable Interest Entity, Classification [Domain] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Commodity Contract [Member] Commodity derivatives Common Shares Common Stock [Member] Common Stock, Value, Issued Common shares, $0.01 par value; 2,000,000,000 authorized shares; 391,423,703 and 390,530,946 issued at December 31, 2012 and 2011, respectively Common Stock, Shares, Issued Common shares, issued shares Common Stock, Par or Stated Value Per Share Common shares, par value (in dollars per share) Common Stock, Shares Authorized Common shares, authorized shares 401(k) Plan Components of deferred income tax assets and liabilities Components of Deferred Tax Assets and Liabilities [Abstract] Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Concentration Risk, Credit Risk, Policy [Policy Text Block] Concentration of Credit Risk Schedule I Condensed Parent Company Financial Statements Condensed Financial Information of Parent Company Only Disclosure [Text Block] Schedule I Condensed Parent Company Financial Statements Consolidation, Policy [Policy Text Block] Principles of Consolidation Consolidation, Variable Interest Entity, Policy [Policy Text Block] Variable Interest Entity Schedule of future minimum rental commitments under various operating leases Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block] Conversion of Stock [Line Items] Number of common shares into which the convertible preferred units were exchanged Convertible Preferred Units Conversion of Stock, Shares Issued Number of common shares into which the units were exchanged Number of common shares into which the units were exchanged Conversion of Stock [Table] Convertible Preferred Stock [Member] Convertible preferred units Costs and Expenses [Abstract] Costs and expenses: Costs and Expenses Total costs and expenses Credit Facility [Domain] Credit Facility [Axis] Current Current Income Tax Expense (Benefit) Debt Instrument, Description of Variable Rate Basis Variable rate basis Debt Disclosure [Text Block] Debt Debt Debt Instrument, Basis Spread on Variable Rate Applicable margin (as a percent) Total deferred tax assets, net Deferred Tax Assets, Net of Valuation Allowance [Abstract] Deferred Compensation Arrangements [Abstract] Compensation agreement Title of Individual [Axis] Deferred financing costs and other assets Deferred Costs and Other Assets Deferred Finance Costs, Noncurrent, Gross Deferred financing costs Total deferred tax liabilities Deferred Tax Liabilities, Gross Deferred Finance Costs, Noncurrent, Net Deferred financing costs, net of accumulated amortization of $13,922 and $6,582, respectively Deferred financing costs, net of accumulated amortization of $283 and zero, respectively Deferred income taxes Deferred Income Tax Expense (Benefit) Deferred Total deferred tax assets, net Deferred Tax Assets, Net of Valuation Allowance Current deferred tax assets Deferred Tax Assets, Net, Current Net deferred tax asset (liability) Deferred Tax Assets, Net Unrealized derivative losses Deferred Tax Assets, Derivative Instruments Total deferred tax assets Deferred Tax Assets, Gross Total deferred tax assets Long-term deferred tax assets Deferred Tax Assets, Net, Noncurrent Other Deferred Tax Assets, Other Equity compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Foreign net operating losses Deferred Tax Assets, Operating Loss Carryforwards, Foreign Valuation allowance Deferred Tax Assets, Valuation Allowance Valuation allowance Other Deferred Tax Liabilities, Other Deferred Tax Liabilities, Net, Noncurrent Deferred tax liability Depletion, depreciation and amortization related to property and equipment Deferred Tax Liabilities, Property, Plant and Equipment Deferred tax liabilities: Deferred Tax Liabilities, Gross [Abstract] Maximum employee contributions as percentage of compensation matched by the Company Defined Contribution Plan, Employer Matching Contribution, Percent Company's matching contribution to the 401(k) Plan Defined Contribution Plan, Cost Recognized Depletion of Oil and Gas Properties Depletion expense Depreciation, Depletion, and Amortization [Policy Text Block] Depletion, Depreciation and Amortization Depletion, depreciation and amortization Depreciation, Depletion and Amortization Weighted average ceiling price per Bbl Derivative, Average Cap Price Derivative Liabilities, Current Derivatives Derivatives liabilities - current Derivative Assets, Noncurrent Derivatives Derivative Instrument Risk [Axis] Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Amount of Gain/(Loss), derivatives not designated as hedging instruments Derivative Assets Derivative asset, fair value Derivative Assets (Liabilities), at Fair Value, Net Total Derivative [Line Items] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Financial Instruments Derivative, Average Fixed Interest Rate Weighted Average Fixed Rate (as a percent) Derivative Financial Instruments, Liabilities, Fair Value Disclosure Derivative liability, fair value Derivative Assets, Current Derivatives Derivatives assets - current Derivative [Table] Derivative Financial Instruments Derivative [Member] Derivatives, net Derivative Liabilities, Noncurrent Derivatives Derivatives liabilities - long-term Weighted average floor price per Bbl Derivative, Average Floor Price Derivative, Description of Variable Rate Basis Floating Rate Total derivatives in cash flow hedging relationships Derivative, Gain (Loss) on Derivative, Net Derivative, by Nature [Axis] Weighted average call price per Bbl Derivative, Average Price Risk Option Strike Price Amount of Gain/(Loss) reclassified from AOCI into earnings Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Hedging Relationship [Axis] Derivative, Name [Domain] Derivative Contract Type [Domain] Derivative Instruments, Gain (Loss) [Line Items] Derivative instruments, Location of Gain/(Loss) Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Amount of Gain/(Loss) recorded in AOCI Derivatives, Policy [Policy Text Block] Derivative Instruments and Hedging Activities Derivatives, Fair Value [Line Items] Derivative instruments, Balance Sheet Location Pro forma diluted (in dollars per share) Diluted Earnings Per Share Pro Forma Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Equity-based Compensation Equity-based Compensation Receivables from subsidiaries Due from Affiliate, Current Diluted (in dollars per share) Earnings Per Share, Diluted Basic (in dollars per share) Earnings Per Share, Basic Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Net income (loss) per share Earnings Per Share [Text Block] Net Income (Loss) Per Share Net Income (Loss) Per Share Net loss per share attributable to common shareholders: Net income (loss) per share attributable to common shareholders (the year ended December 31, 2011 represents the period from May 16, 2011 to December 31, 2011) (Note 16): Reconciliation of differences between applicable statutory tax rate and effective income tax rate Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract] Effective Income Tax Rate, Continuing Operations Effective tax rate (as a percent) Consolidated effective tax rate (as a percent) Income/loss subject to tax in excess of statutory rate (as a percent) Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate Statutory rate (as a percent) Tax provision at statutory rate (Bermuda) (as a percent) Applicable foreign statutory tax rate (as a percent) Change in valuation allowance (as a percent) Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance Other (as a percent) Effective Income Tax Rate Reconciliation, Other Adjustments Provisional Oil Sales Embedded Derivative Financial Instruments [Member] Oil and gas revenue Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition Weighted average period over which compensation expense is to be recognized Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Tax benefit Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized Compensation expense not yet recognized Employee Service Share-based Compensation, Aggregate Disclosures [Abstract] Compensation agreement Hydrocarbons inventory Energy Related Inventory, Petroleum Convertible Preferred Units Investment in subsidiaries at equity Equity Method Investments Equity Method Investment, Ownership Percentage Investment in subsidiaries (as a percent) Equity Method Investment, Underlying Equity in Net Assets Investment in subsidiaries at equity Equity Component [Domain] Estimate of Fair Value, Fair Value Disclosure [Member] Total Exploration Expense Exploration expenses Exploratory Drilling Costs Capitalization and Impairment, Policy [Policy Text Block] Exploration and Development Costs Exploratory Wells Drilled [Table] Exploratory Wells Drilled, Net Productive Number of appraisal wells which were drilled Exploratory Wells Drilled [Line Items] Projects with exploratory well costs capitalized for more than one year Jubilee field unitization Commitment amount cancelled Extinguishment of Debt, Amount Measurement Frequency [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Recurring [Member] Recurring basis Fair Value, Measurement Frequency [Domain] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Measurements Fair Value Measurements Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value, Inputs, Level 1 [Member] Level 1 Fair Value, Inputs, Level 2 [Member] Level 2 Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Foreign Currency Transactions and Translations Policy [Policy Text Block] Foreign Currency Translation Gains (Losses) on Extinguishment of Debt Loss on extinguishment of debt Common Units General Partner [Member] General and administrative General and Administrative Expense Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Hedging Designation [Axis] Hedging Relationship [Domain] Hedging Designation [Domain] Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Impairment of Long-lived Assets Incentive from Lessor Leasehold improvement allowance CONSOLIDATED STATEMENTS OF OPERATIONS Income Statement Location [Axis] Income Taxes Income Tax Disclosure [Text Block] Income Taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Income (loss) before income taxes Profit before taxes Income Statement Location [Domain] Components of the provision for income taxes attributable to income (loss) before income taxes Income Tax Expense (Benefit), Continuing Operations [Abstract] Income Tax Expense (Benefit) Income tax expense (benefit) Income tax expense (benefit) Income tax expense (benefit) Income tax expense Tax at Bermuda statutory rate Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate Reconciliation of income expense (benefit)and income (loss) from continuing operations is as follows: Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract] Non-deductible and other items Income Tax Reconciliation, Nondeductible Expense Change in valuation allowance Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance Foreign income taxed at different rates Income Tax Reconciliation, Foreign Income Tax Rate Differential Tax shortfall on equity-based compensation Income Tax Reconciliation, Nondeductible Expense, Share-based Compensation Cost Tax shortfall related to equity-based compensation Income Tax, Policy [Policy Text Block] Income Taxes Income Taxes Paid Income taxes Impact of losses incurred in jurisdictions in which company is not subject to taxes on effective tax rate Income Tax Reconciliation, Tax Holidays Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward] Reconciliation of capitalized exploratory well costs on completed wells Increase (Decrease) in Accounts Payable Increase (decrease) in accounts payable Increase (decrease) in accrued liabilities Increase (Decrease) in Accrued Liabilities Increase in accrued liabilities Settlement of previously recognized hedge losses Increase (Decrease) in Derivative Assets and Liabilities Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] (Increase) decrease in prepaid expenses and other Increase (Decrease) in Prepaid Expense and Other Assets (Increase) decrease in inventories Increase (Decrease) in Inventories Restricted cash Increase (Decrease) in Restricted Cash Additional restricted cash related to cash collateralization for performance guarantees (Increase) decrease in receivables Increase (Decrease) in Receivables Increase (Decrease) in Shareholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Incremental Common Shares Attributable to Share-based Payment Arrangements Restricted stock awards (in shares) Interest Payable, Current Accrued interest Interest Costs Capitalized Capitalized interest Interest Expense Interest expense Interest Capitalization, Policy [Policy Text Block] Capitalized Interest Interest Expense, Debt Interest expense, net of capitalized interest Interest Rate Swap [Member] Interest Rate Swaps Interest Interest Paid Interest Rate Contract [Member] Interest rate contracts Interest rate derivatives Interest Expense [Member] Interest expense Inventory, Policy [Policy Text Block] Inventories Inventory, Net [Abstract] Inventories Inventory, Net Inventories Inventory, Supplies, Net of Reserves Materials and supplies inventory Leasehold Improvements [Member] Leasehold improvements Liabilities, Current Total current liabilities Liabilities, Noncurrent Total long-term liabilities Current liabilities: Liabilities, Current [Abstract] Liabilities, Noncurrent [Abstract] Long-term liabilities: Liabilities and shareholders' equity Liabilities and Equity [Abstract] Liabilities and shareholders' equity/unit holdings equity Liabilities, Fair Value Disclosure [Abstract] Liabilities: Liabilities and Equity Total liabilities and shareholders' equity Line of Credit Facility, Maximum Borrowing Capacity Borrowing Capacity Percentage of the margin used to calculate commitment fees Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Line of Credit Facility, Remaining Borrowing Capacity Undrawn availability Borrowings Line of Credit Facility, Amount Outstanding Line of Credit Facility [Line Items] Debt Line of Credit Facility [Table] Total Long-term Debt Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year 2013 Long-term Debt, Fiscal Year Maturity [Abstract] Scheduled maturities of debt during the five year period and thereafter Facility Long-term Purchase Commitment [Table] Long-term Purchase Commitment [Line Items] Commitments and Contingencies Long-term Debt, Maturities, Repayments of Principal in Year Three 2015 Long-term Debt, Maturities, Repayments of Principal in Year Two 2014 Long-term Debt, Maturities, Repayments of Principal in Year Four 2016 Long-term Debt, Maturities, Repayments of Principal in Year Five 2017 Category of Item Purchased [Axis] Long-term Debt, Current Maturities Current maturities of long-term debt Long-term Debt, Excluding Current Maturities Long-term debt Long-term Debt, Maturities, Repayments of Principal after Year Five Thereafter Long-term Purchase Commitment, Category of Item Purchased [Domain] Maximum [Member] Maximum Minimum [Member] Minimum Money Market Funds, at Carrying Value Money market accounts Changes in valuation and qualifying Accounts Movement in Valuation Allowances and Reserves [Roll Forward] Nature of Error [Domain] Nature of Operations [Text Block] Organization Financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations Operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net increase (decrease) in cash and cash equivalents Net Cash Provided by (Used in) Continuing Operations Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations Basic net income (loss) allocable to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Numerator: Net Income (Loss) Available to Common Stockholders, Diluted Diluted net income (loss) allocable to common shareholders Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations Investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Net income (Loss) attributable to common shareholders/unit holders Net Income (Loss) Attributable to Parent Net loss attributable to common shareholders/unit holders New Accounting Pronouncements, Policy [Policy Text Block] Recent Accounting Standards Noncash Investing and Financing Items [Abstract] Non-cash activities: Nonoperating Income (Expense) Other expenses, net Notes, Loans and Financing Receivable, Net, Current Notes Notional Amount of Interest Rate Derivatives Weighted Average Notional Amount Notional amount Number of Operating Segments Number of business segments Number of Reportable Segments Number of reportable segments Not Designated as Hedging Instrument [Member] Not designated as hedging instruments Oil and Gas Joint Interest Billing Receivables, Current Joint interest billings Current joint interest billings Total oil and gas properties Oil and Gas Property, Successful Effort Method, Gross Oil and Gas Sales Revenue Oil and gas revenue Suspended Well Costs Oil and Gas Property, Successful Effort Method, Net [Abstract] Oil and gas properties: Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization Oil and gas properties, accumulated depletion (in dollars) Less: accumulated depletion Oil and Gas Joint Interest Billing Receivables, Noncurrent Long-term receivables - joint interest billings, net of allowance of zero and $39.8 million, respectively Oil and Gas Production Expense Oil and gas production Oil and Gas Property, Successful Effort Method, Net Oil and gas properties Oil and gas properties, net Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Operating leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Rent expense Operating Leases, Rent Expense, Net 2015 Operating Leases, Future Minimum Payments, Due in Three Years 2014 Operating Leases, Future Minimum Payments, Due in Two Years 2013 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2016 Operating Leases, Future Minimum Payments, Due in Four Years 2017 Operating Leases, Future Minimum Payments, Due in Five Years Total Operating Leases, Future Minimum Payments Due Organization Other Other Noncash Income (Expense) Other Receivables, Net, Current Other Other receivables Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax Reclassification adjustments for derivative losses included in net income (loss) Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax Derivatives, net Other Assets, Noncurrent [Abstract] Other assets: Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Change in fair value of cash flow hedges Other Nonoperating Income Interest income Other Liabilities, Noncurrent Other long-term liabilities Other Revenue, Net Other income Other comprehensive income : Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax, Portion Attributable to Parent Income tax benefit Kosmos Energy Holdings Predecessor [Member] Parent company Parent Company [Member] Parent Accounts Payable and Accrued Liabilities Payments for (Proceeds from) Investments Notes receivable Payments for Repurchase of Common Stock Purchase of treasury stock Purchase of treasury stock Oil and gas assets Payments to Acquire Oil and Gas Property and Equipment Investment in subsidiaries Payments to Acquire Additional Interest in Subsidiaries Payments of Financing Costs Deferred financing costs Other property Payments to Acquire Other Property, Plant, and Equipment 401(k) Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Performance based restricted stock awards Performance Shares [Member] Petroleum agreements - performance guarantees Performance Guarantee [Member] Plan Name [Domain] Plan Name [Axis] Preferred Stock, Value, Issued Preference shares, $0.01 par value; 200,000,000 authorized shares; zero issued at December 31, 2012 and 2011 Preferred Stock, Shares Authorized Preference shares, authorized shares Preferred Stock [Text Block] Convertible Preferred Units Preferred Stock, Shares Issued Preference shares, issued shares Preferred Stock, Par or Stated Value Per Share Preference shares, par value (in dollars per share) Prepaid Expense and Other Assets, Current Prepaid expenses and other Reclassifications Reclassification, Policy [Policy Text Block] Pro Forma Weighted Average Shares Outstanding, Diluted Pro forma diluted (in shares) Pro forma diluted (in shares) Net proceeds from issuance of units Proceeds from Issuance of Convertible Preferred Stock Net proceeds from issuance of senior notes Proceeds from Issuance of Senior Long-term Debt Proceeds from Issuance of Long-term Debt Borrowings under long-term debt Proceeds from Issuance Initial Public Offering Net proceeds from the initial public offering Net income (loss) Net income (loss) Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects Number of projects that have exploratory well costs that have been capitalized for a period greater than one year Property, Plant and Equipment, Useful Life Estimated useful lives (in years) Property and equipment: Property, Plant and Equipment, Net [Abstract] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Other, Gross Other property Property and Equipment Property, Plant and Equipment, Other, Net Other property Other property, net Property, Plant and Equipment, Other, Accumulated Depreciation Less: Accumulated depreciation Property, Plant and Equipment, Net Property and equipment, net Property, Plant and Equipment [Line Items] Depreciation and amortization Property and Equipment Property, Plant and Equipment [Table Text Block] Schedule of property and equipment Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment Disclosure [Text Block] Property and Equipment Proved Oil and Gas Property, Successful Effort Method Proved properties Purchased Puts Purchased Put Option [Member] Purchased Calls Purchased Call Option [Member] Quantifying Misstatement in Current Year Financial Statements, Amount Capitalization, which was previously recorded as exploration expense Quantifying Misstatement in Current Year Financial Statements [Line Items] Correction of immaterial error by capitalization Nature of Error [Axis] Range [Axis] Range [Domain] Receivables: Receivables, Net, Current [Abstract] Receivables, Policy [Policy Text Block] Receivables Reclassification due to determination of proved reserves Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves General and administrative - related party Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party Repayments of Long-term Debt Payments on long-term debt Restricted stock units Restricted Stock Units (RSUs) [Member] Restricted cash Restricted Cash and Cash Equivalents Cash and Cash Equivalents [Domain] Restricted Stock [Member] Restricted stock awards Service Vesting Restricted Stock Awards Restricted Cash and Cash Equivalents [Axis] Restricted Cash and Cash Equivalents, Current Restricted cash Current restricted cash Restricted Cash Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash and Cash Equivalents, Noncurrent Restricted cash Long-term restricted cash Additional long-term restricted cash Results of Operations, Dry Hole Costs Unsuccessful well costs Unsuccessful well costs Depletion and depreciation Results of Operations, Depreciation, Depletion, Amortization and Accretion Retained Earnings (Accumulated Deficit) Accumulated deficit Accumulated Deficit Retained Earnings [Member] Revenue Recognition, Policy [Policy Text Block] Revenue Recognition Revenues Total revenues and other income Revolving Credit Facility [Member] Corporate Revolver Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Expected life Revenue, Net [Abstract] Revenues and other income: Sales [Member] Oil and gas revenue Scenario, Unspecified [Domain] Schedule of Aging of Capitalized Exploratory Well Costs [Table Text Block] Schedule of aging of capitalized exploratory well costs and number of projects for which exploratory well costs were capitalized for more than one year Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Company's assets and liabilities that are measured at fair value on a recurring basis Schedule of Change in Asset Retirement Obligation [Table Text Block] Schedule of changes in asset retirement obligations Schedule of equity-based incentive awards activity Schedule of Nonvested Share Activity [Table Text Block] Schedule of components of income (loss) before income taxes Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Schedule of Maturities of Long-term Debt [Table Text Block] Schedule of maturities of debt Schedule of reconciliation of profit before taxes to total tax expense Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Accrued Liabilities [Table Text Block] Schedule of components of accrued liabilities Schedule of Share-based Compensation, Activity [Table Text Block] Schedule of plan activity Schedule of tax effects of significant temporary differences to deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Interest Rate Derivatives [Table Text Block] Schedule of interest rate swaps derivative contracts Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Schedule of plan activity Schedule of calculation of the numerator and denominator used in earnings per share Schedule of Calculation of Numerator and Denominator in Earnings Per Share [Table Text Block] Schedule of Price Risk Derivatives [Table Text Block] Schedule of oil derivative contracts Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Significant Acquisitions and Disposals [Table] Schedule of Quantifying Prior Year Misstatement Corrected in Current Year Financial Statements [Table] Schedule of Property, Plant and Equipment [Table] Schedule of Restricted Cash and Cash Equivalents [Table] Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Schedule II Valuation and Qualifying Accounts Schedule of derivative instruments by balance sheet location Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Schedule of Variable Interest Entities [Table] Schedule of derivative instruments by location of gain/(loss) Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block] Series A Convertible Preferred Units Series A Preferred Stock [Member] Series C Convertible Preferred Units Series C Preferred Stock [Member] Series B Convertible Preferred Units Series B Preferred Stock [Member] Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract] Other disclosures Outstanding at the beginning of the period (in shares) Outstanding at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Outstanding unvested awards activity Share-based Compensation Equity-based compensation Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures and Expirations Relinquished (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Granted (in dollars per share) Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Outstanding at the end of the period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Outstanding at beginning of the period (in dollars per share) Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] Weighted-Average Grant-Date Fair Value Equity-based Compensation Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Outstanding at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Outstanding at the beginning of the period (in shares) Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] Outstanding awards activity Original unit purchase price (in dollars per share) Share Price Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Risk-free interest rate (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Expected volatility (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Awards available for future grant (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Approved and authorized awards (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Significant assumptions used to calculate fair values Awards issued after May 16, 2011 (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Award Type [Domain] Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Equity-based Compensation Shares, Issued Balance (in shares) Balance (in shares) Significant Accounting Policies [Text Block] Accounting Policies Significant Acquisitions and Disposals [Line Items] Acquisition of FPSO Significant Acquisitions and Disposals, Transaction [Domain] Significant Acquisitions and Disposals by Transaction [Axis] Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds Acquisition cost Letter of Credit Standby Letters of Credit [Member] Statement [Table] Scenario [Axis] Statement [Line Items] Statement CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY CONSOLIDATED STATEMENTS OF CASH FLOWS Equity Components [Axis] CONSOLIDATED BALANCE SHEETS CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) Class of Stock [Axis] Stock Issued During Period, Value, Conversion of Units Common and restricted shares issued upon corporate reorganization Effect of exchange on book value of shareholder's equity Stock Issued During Period, Shares, Period Increase (Decrease) Stock Issued During Period, Shares, Conversion of Units Common and restricted shares issued upon corporate reorganization (in shares) Number of common shares into which the units were exchanged Number of restricted shares issued to management and employees (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Restricted stock awards (in shares) Stock Issued During Period, Value, Restricted Stock Award, Gross Restricted stock awards Stock Issued During Period, Value, New Issues Common shares issued at initial public offering, net of offering costs Issuance of C1 units (in shares) Stock Issued During Period, Shares, Other Stock Issued During Period, Value, Share-based Compensation, Forfeited Relinquishments of profit units Stock Issued During Period, Shares, New Issues Common shares issued at initial public offering, net of offering costs (in shares) Common shares issued Total number of common shares sold under the IPO Stock Issued During Period, Value, Restricted Stock Award, Forfeitures Restricted stock forfeitures Stock Issued During Period, Value, Share-based Compensation, Gross Issuance of profit units Stock Issued During Period, Shares, Share-based Compensation, Gross Issuance of profit units (in shares) Stock Issued During Period, Value, Other Issuance of C1 units Shareholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Total shareholders' equity Balance Balance Stockholders' Equity Attributable to Parent Total shareholders' equity/unit holdings equity Stockholders' Equity, Period Increase (Decrease) Subsequent Event Subsequent Events [Text Block] Subsequent Event Subsequent Event Type [Domain] Subsequent events Subsequent Event [Line Items] Subsequent Event Type [Axis] Subsequent Event [Table] Subsequent event Subsequent Event [Member] Subsidiaries [Member] Kosmos Energy Holdings Supplemental cash flow information Supplemental Cash Flow Information [Abstract] Suspended Well Costs Disclosure [Text Block] Suspended Well Costs Convertible preferred units Temporary Equity, Carrying Amount, Attributable to Parent Temporary Equity, Shares Authorized Convertible preferred units, units authorized Temporary Equity, Shares Issued Convertible preferred units, units issued Temporary Equity [Abstract] Convertible preferred units, 100,000,000 units authorized: Plus: Accretion to redemption value of convertible preferred units Temporary Equity, Accretion to Redemption Value, Adjustment Accretion to redemption value of convertible preferred units Accretion amount Title of Individual with Relationship to Entity [Domain] Treasury Stock, Value Treasury stock, at cost, 2,731,941 and 649,818 shares at December 31, 2012 and 2011, respectively Treasury stock, at cost, 2,731,941 and 649,818 shares at December 31, 2012 and 2011, respectively Purchase of treasury stock (in shares) Treasury Stock, Shares, Acquired Treasury Stock, Shares Treasury stock, shares Treasury Stock Treasury Stock [Member] Purchase of treasury stock Treasury Stock, Value, Acquired, Cost Method Undistributed Earnings Allocated to Participating Securities Less: Basic income allocable to participating securities Unproved Oil and Gas Property, Successful Effort Method Unproved properties Unrealized Gain (Loss) on Cash Flow Hedging Instruments Change in fair value of cash flow hedges Unrealized Gain (Loss) on Derivatives Non-cash change in fair value of derivatives Use of Estimates, Policy [Policy Text Block] Use of Estimates Valuation and Qualifying Accounts Disclosure [Table] Net change in valuation allowance on deferred tax assets Valuation Allowance, Deferred Tax Asset, Change in Amount Valuation Allowances and Reserves [Domain] Charged to Costs and Expenses Valuation Allowances and Reserves, Charged to Cost and Expense Balance at the beginning of the period Balance at the end of the period Valuation Allowances and Reserves, Balance Deductions From Reserves Valuation Allowances and Reserves, Deductions Allowance for deferred tax asset Valuation Allowance of Deferred Tax Assets [Member] Charged To Other Accounts Valuation Allowances and Reserves, Charged to Other Accounts Schedule II Valuation and Qualifying Accounts Valuation and Qualifying Accounts Valuation and Qualifying Accounts Disclosure [Line Items] Valuation Allowances and Reserves Type [Axis] Variable Interest Entity, Primary Beneficiary [Member] Kosmos Energy Finance International Variable Interest Entity [Line Items] Variable interest entity Variable Interest Entities [Axis] Vehicles [Member] Vehicles Weighted Average Number of Shares Outstanding, Diluted [Abstract] Weighted average number of shares used to compute net income (loss) per share (the year ended December 31, 2011 represents the period from May 16, 2011 to December 31, 2011) (Note 16): Weighted average number of shares used to compute net income (loss) per share: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Denominator: Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Diluted (in shares) Weighted Average Basic Shares Outstanding, Pro Forma Pro forma basic (in shares) Long-term Debt, Other Disclosures [Abstract] Other disclosures Nonmonetary Notional Amount Of Price Risk Derivatives1 Aggregate notional amount of price risk derivatives for instruments with notional amounts expressed in nonmonetary units. Volumes (in MBbl)