Cobalt International Energy 10-K 27 Feb 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2013	Jun. 30, 2013
Document and Entity Information	'	'
Entity Registrant Name	'Cobalt International Energy, Inc.	'
Entity Central Index Key	'0001471261	'
Document Type	'10-K	'
Document Period End Date	31-Dec-13	'
Amendment Flag	'false	'
Current Fiscal Year End Date	'--12-31	'
Entity Well-known Seasoned Issuer	'Yes	'
Entity Voluntary Filers	'No	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Public Float	'	$7.50
Entity Common Stock, Shares Outstanding	411,284,727	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'FY	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$192,460	$1,425,815
Joint interest and other receivables	124,639	61,592
Prepaid expenses and other current assets	55,857	23,941
Inventory	74,768	65,286
Short-term restricted funds	200,339	90,440
Short-term investments	1,319,380	789,668
Total current assets	1,967,443	2,456,742
Property, plant, and equipment:	'	'
Oil and gas properties, successful efforts method of accounting, net of accumulated depletion of $0	1,464,383	1,094,464
Other property and equipment, net of accumulated depreciation and amortization of $4,394 and $2,533, as of December 31, 2013 and 2012, respectively	11,892	5,292
Total property, plant, and equipment, net	1,476,275	1,099,756
Long-term restricted funds	104,496	395,652
Long-term investments	14,661	36,267
Deferred income taxes	17,061	'
Other assets	53,737	23,042
Total assets	3,633,673	4,011,459
Current liabilities:	'	'
Trade and other accounts payable	131,428	67,876
Accrued liabilities	143,459	44,061
Short-term contractual obligations	49,019	49,019
Deferred income taxes	17,061	'
Total current liabilities	340,967	160,956
Long-term debt	1,035,980	991,191
Long-term contractual obligations	124,901	168,238
Other long-term liabilities	2,679	1,856
Total long-term liabilities	1,163,560	1,161,285
Stockholders' equity:	'	'
Common stock, $0.01 par value per share; 2,000,000,000 shares authorized 406,949,839 and 406,596,884 issued and outstanding as of December 31, 2013 and 2012, respectively	4,069	4,066
Additional paid-in capital	3,641,936	3,612,987
Accumulated deficit during the development stage	-1,516,859	-927,835
Total stockholders' equity	2,129,146	2,689,218
Total liabilities and stockholders' equity	$3,633,673	$4,011,459

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Consolidated Balance Sheets	'	'
Oil and gas properties, successful efforts method of accounting, accumulated depletion (in dollars)	$0	$0
Other property and equipment, accumulated depreciation and amortization (in dollars)	$4,394	$2,533
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares issued	406,949,839	406,596,884
Common stock, shares outstanding	406,949,839	406,596,884

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended			98 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Operating costs and expenses:	'	'	'	'
Seismic and exploration	$74,213	$61,583	$32,239	$464,385
Dry hole expense and impairment	351,050	134,085	45,732	589,783
General and administrative	105,547	87,963	59,130	411,489
Depreciation and amortization	1,874	1,197	735	6,626
Total operating costs and expenses	532,684	284,828	137,836	1,472,283
Operating income (loss)	-532,684	-284,828	-137,836	-1,472,283
Other income (expense):	'	'	'	'
Gain on sale of assets	2,993	'	'	2,993
Interest income	6,043	5,041	4,199	21,087
Interest expense	-65,376	-3,212	'	-68,656
Total other income (expense)	-56,340	1,829	4,199	-44,576
Net income (loss) before income tax	-589,024	-282,999	-133,637	-1,516,859
Income tax expense	0	0	0	'
Net income (loss)	($589,024)	($282,999)	($133,637)	($1,516,859)
Basic and diluted income (loss) per common share (in dollars per share)	($1.45)	($0.70)	($0.35)	'
Basic and diluted weighted average common shares outstanding (in shares)	406,839,997	403,356,174	376,603,520	'

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Partners' Capital and Stockholders' Equity (USD $)	Total	Class A Limited Partners	Class B Limited Partners	Class C Limited Partners	Common Stock	Additional Paid-in Capital	Accumulated Deficit During Development Stage
In Thousands
Balance (inception) at Dec. 31, 2008	$740,471	$1,029,572	$4,365	'	'	'	($293,466)
Class A limited partners' contributions	227,166	227,166	'	'	'	'	'
Class B and C limited partners' equity compensation	3,353	'	2,619	734	'	'	'
Common stock issued for restricted stock, restricted stock units and stock options	'	'	'	'	22	-22	'
Common stock issued upon corporate reorganization	'	-1,256,738	-6,984	-734	2,743	1,261,713	'
Equity based compensation	15,074	'	'	'	'	15,074	'
Common stock issued at initial public offering including over-allotment portion, net of offering costs	908,515	'	'	'	710	907,805	'
Common stock issued at private placement	42,188	'	'	'	32	42,156	'
Net income (loss)	-217,733	'	'	'	'	'	-217,733
Balance at Dec. 31, 2010	1,719,034	'	'	'	3,507	2,226,726	-511,199
Common stock issued at public offering, net of costs	478,203	'	'	'	357	477,846	'
Common stock issued for restricted stock, restricted stock units and stock options	'	'	'	'	12	-12	'
Equity based compensation	15,505	'	'	'	'	15,505	'
Common stock withheld for taxes on equity based compensation	-191	'	'	'	-1	-190	'
Net income (loss)	-133,637	'	'	'	'	'	-133,637
Balance at Dec. 31, 2011	2,078,914	'	'	'	3,875	2,719,875	-644,836
Common stock issued at public offering, net of costs	489,309	'	'	'	181	489,128	'
Common stock issued for restricted stock, restricted stock units and stock options	'	'	'	'	10	-10	'
Equity based compensation	22,410	'	'	'	'	22,410	'
Exercise of stock options	338	'	'	'	'	338	'
Common stock withheld for taxes on equity based compensation	-170	'	'	'	'	-170	'
Conversion option relating to 2.625% convertible senior notes, net of allocated costs	381,416	'	'	'	'	381,416	'
Net income (loss)	-282,999	'	'	'	'	'	-282,999
Balance at Dec. 31, 2012	2,689,218	'	'	'	4,066	3,612,987	-927,835
Common stock issued for restricted stock, restricted stock units and stock options	'	'	'	'	3	-3	'
Equity based compensation	28,754	'	'	'	'	28,754	'
Exercise of stock options	198	'	'	'	'	198	'
Net income (loss)	-589,024	'	'	'	'	'	-589,024
Balance at Dec. 31, 2013	$2,129,146	'	'	'	$4,069	$3,641,936	($1,516,859)

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Partners' Capital and Stockholders' Equity (Parenthetical)	Dec. 31, 2012
Condensed Consolidated Statements of Changes in Partners' Capital and Stockholders' Equity	'
Interest rate (as a percent)	2.63%

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended			98 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Cash flows provided from operating activities	'	'	'	'
Net income (loss)	($589,024)	($282,999)	($133,637)	($1,516,859)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'	'
Depreciation and amortization	1,874	1,197	735	6,626
Dry hole expense and impairment	351,050	134,085	45,732	589,783
Gain on sale of assets	-2,993	'	'	-2,993
Equity based compensation	28,754	22,410	15,505	89,461
Amortization of premium (accretion of discount)	21,955	15,091	22,082	56,497
Amortization of debt discount	46,847	'	'	48,520
Other	'	'	'	580
Changes in operating assets and liabilities:	'	'	'	'
Joint interest and other receivables	-62,967	-1,518	-59,515	-128,161
Inventory	-10,052	-29,237	-1,621	-75,338
Prepaid expense and other current assets	-31,915	-1,726	-13,209	-55,857
Deferred charges	-32,753	-10,985	2,467	-32,679
Trade and other accounts payable	63,552	-3,309	59,196	131,428
Accrued liabilities and other	-696	16,594	4,470	47,071
Net cash provided by (used in) operating activities	-216,368	-140,397	-57,795	-841,921
Cash flows from investing activities	'	'	'	'
Capital expenditures for oil and gas properties	-80,439	-142,841	'	-927,387
Capital expenditures for other property and equipment	-8,483	-5,139	-782	-18,549
Exploration wells drilling in process	-581,194	-329,534	-86,979	-1,192,169
Proceeds from sale of oil and gas properties	3,006	'	'	342,007
Change in restricted cash	180,729	29,573	-541	-131,353
Proceeds from maturity of investment securities	1,366,977	1,082,876	1,288,067	3,966,031
Purchase of investment securities	-1,896,591	-1,199,696	-1,630,156	-5,526,528
Net cash provided by (used in) investing activities	-1,015,995	-564,761	-430,391	-3,487,948
Cash flows from financing activities	'	'	'	'
Capital contributions prior to IPO-Class A limited partners	'	'	'	1,256,180
Proceeds from initial public offering, net of costs	'	'	'	950,702
Proceeds from public offering, net of costs	'	489,309	478,203	967,513
Proceeds from debt offering, net of costs	-1,190	1,348,950	'	1,347,760
Proceed from exercise of stock options	198	338	'	536
Payments for common stock withheld for taxes on equity based compensation	'	-170	-191	-362
Net cash provided by (used in) financing activities	-992	1,838,427	478,012	4,522,329
Net increase (decrease) in cash and cash equivalents	-1,233,355	1,133,269	-10,174	192,460
Cash and cash equivalents, beginning of period	1,425,815	292,546	302,720	'
Cash and cash equivalents, end of period	192,460	1,425,815	292,546	192,460
Cash paid for interest	34,615	'	'	34,615
Non-Cash Disclosures	'	'	'	'
Change in accrued capital expenditures	58,769	-105,802	357,900	58,769
Transfer of investment securities to and from restricted funds	$26	$178,830	'	$178,804

Organization_and_Operations

Organization and Operations	12 Months Ended
	Dec. 31, 2013
Organization and Operations	'
Organization and Operations	'
	1. Organization and Operations
	Organization
	Cobalt International Energy, Inc. (the "Company") is an independent exploration and production company with operations in the deepwater U.S. Gulf of Mexico and offshore Angola and Gabon in West Africa.
	The terms "Company, Cobalt, we, us, our, ours," and similar terms refer to Cobalt International Energy, Inc. unless the context indicates otherwise.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Summary of Significant Accounting Policies	'
	2. Summary of Significant Accounting Policies
	Basis of Presentation
	The accompanying consolidated financial statements include the financial statements of Cobalt International Energy, Inc. and all of its wholly owned subsidiaries. All significant intercompany transactions and amounts have been eliminated for all years presented. Because the Company is a development stage enterprise, it has presented its financial statements in accordance with accounting guidance relating to "Development Stage Entities."
	At December 31, 2013, the accompanying consolidated financial statements include the accounts of Cobalt and its wholly owned subsidiary, Cobalt International Energy, L.P. ("Partnership"). Prior to the effective date of a corporate reorganization, both entities were under common control arising from common direct or indirect ownership of each. The transfer of the Partnership interests to Cobalt represented a reorganization of entities under common control and was accounted for at historical cost.
	Reclassifications
	Certain reclassifications have been made to prior periods' financial statements to conform to the current presentation in the consolidated statements of cash flows.
	Use of Estimates
	The preparation of financial statements in conformity with United States generally accepted accounting principles ("GAAP") requires the Company to make estimates and assumptions that affect the reported amounts of assets including proved reserves and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates the Company makes include (a) accruals related to expenses, (b) assumptions used in estimating fair value of equity based awards and the fair value of the liability component of the convertible senior notes and (c) assumptions used in impairment testing. Although the Company believes these estimates are reasonable, actual results could differ from these estimates.
	Fair Value Measurements
	The fair values of the Company's cash and cash equivalents, joint interest and other receivables, restricted funds and investments approximate their carrying amounts due to their short-term duration. The hierarchy below lists three levels of fair value based on the extent to which inputs used in measuring fair value are observable in the market. The Company categorizes each of its fair value measurements as applicable to one of these three levels based on the lowest level input that is significant to the fair value measurement in its entirety. The levels are:
	Level 1—Quoted prices in active markets that are accessible at the measurement date for identical assets or liabilities. This category includes the Company's cash and money market funds.
	Level 2—Quoted prices in non-active markets or in active markets for similar assets or liabilities, and inputs other than quoted prices that are observable, for the asset or liability, either directly or indirectly for substantially the full contractual term of the asset or liability being measured. This category includes the Company's U.S. Treasury bills, U.S. Treasury notes, U.S. Government agency securities, commercial paper, corporate bonds, municipal bonds and certificates of deposits.
	Level 3—Inputs that are generally unobservable and typically reflect management's estimate of assumptions that market participants would use in pricing the asset or liability. The Company does not currently have any financial instruments categorized as Level 3.
	Revenue Recognition
	The Company will follow the "sales" (or cash) method of accounting for oil and gas revenues. Under this method, the Company will recognize revenues on the volumes sold. The volumes sold may be more or less than the volumes to which the Company is entitled based on its ownership interest in the property. These differences result in a condition known in the industry as a production imbalance. For the years ended December 31, 2013, 2012, 2011 and for the period November 10, 2005 (Inception) through December 31, 2013, no revenues have been recognized in these consolidated financial statements.
	Cash and Cash Equivalents
	Cash and cash equivalents consist of demand deposits and funds invested in highly liquid instruments with maturities of three months or less from the date of purchase. Demand deposits typically exceed federally insured limits; however, the Company periodically assesses the financial condition of the institutions where these funds are held as well as the credit ratings of the issuers of the highly liquid instruments and believes that the credit risk is minimal.
	Restricted Funds
	Restricted funds primarily consist of funds held in escrow accounts and collateral for letters of credit relating to our operations in the U.S. Gulf of Mexico and offshore Angola.
	Investments
	The Company's policy on accounting for its investments, which consist entirely of debt securities money market funds and certificates of deposit, is based on the accounting guidance relating to "Accounting for Certain Investments in Debt and Equity Securities." The Company considers all highly liquid interest-earning investments with a maturity of three months or less at the date of purchase to be cash equivalents. Investments with original maturities of greater than three months and remaining maturities of less than one year are classified as short-term investments. Investments with maturities beyond one year are classified as long-term investments. The debt securities are carried at amortized costs and classified as held-to-maturity securities as the Company has the positive intent and ability to hold them until they mature. The net carrying value of held-to-maturity debt securities is adjusted for amortization of premiums and accretion of discounts to maturity over the life of the securities. Held-to-maturity debt securities are stated at amortized cost, which approximated fair market value as of December 31, 2013 and 2012. Money market funds and certificates of deposit are carried at face value. Income related to these securities is reported as a component of interest income in the Company's consolidated statement of operations. See Note 7—Investments.
	Investments are considered to be impaired when a decline in fair value is determined to be other-than-temporary. The Company conducts a regular assessment of its debt securities with unrealized losses to determine whether securities have other-than-temporary impairment ("OTTI"). This assessment considers, among other factors, the nature of the securities, credit rating or financial condition of the issuer, the extent and duration of the unrealized loss, market conditions and whether the Company intends to sell or whether it is more likely than not that the Company will be required to sell the debt securities. As of December 31, 2013 and 2012, the Company has no OTTI in its debt securities.
	Capitalized Interest
	For exploration and development projects that have not commenced production, interest is capitalized as part of the historical cost of developing and constructing assets. Capitalized interest is determined by multiplying the Company's weighted-average borrowing cost on debt by the average amount of qualifying costs incurred. Once an asset subject to interest capitalization is completed and placed in service, the associated capitalized interest is expensed through depreciation or impairment. See Note 9—Property, Plant, and Equipment and Note 11—Long-term Debt.
	Joint Interest and Other Receivables
	Joint interest and other receivables result primarily from billing shared costs under the respective operating agreements to the Company's partners. These receivables are usually settled within 30 days of the invoice date.
	Property, Plant, and Equipment
	The Company uses the "successful efforts" method of accounting for its oil and gas properties. Acquisition costs for unproved leasehold properties and costs of drilling exploration wells are capitalized pending determination of whether proved reserves can be attributed to the areas as a result of drilling those wells. Under the successful efforts method of accounting, proved leasehold costs are capitalized and amortized over the proved developed and undeveloped reserves on a units-of-production basis. Successful drilling costs, costs of development and developmental dry holes are capitalized and amortized over the proved developed reserves on a units-of-production basis. Significant unproved leasehold costs are capitalized and are not amortized, pending an evaluation of their exploration potential. Unproved leasehold costs are assessed periodically to determine if an impairment of the cost of individual properties has occurred. Factors taken into account for impairment analysis include results of the technical studies conducted, lease terms and management's future exploration plans. The cost of impairment is charged to expense in the period in which it occurs. Costs incurred for exploration dry holes, geological and geophysical work (including the cost of seismic data), and delay rentals are charged to expense as incurred. Costs of other property and equipment are depreciated on a straight-line basis based on their respective useful lives.
	Asset Retirement Obligations
	The Company currently does not have any oil and natural gas production or any legal obligations to incur decommissioning costs. Should such production occur in the future, the Company expects to have significant obligations under its lease agreements and federal regulation to remove its equipment and restore land or seabed at the end of oil and natural gas production operations. These asset retirement obligations are primarily associated with plugging and abandoning wells and removing and disposing of offshore oil and natural gas platforms. Estimating the future restoration and removal cost is difficult and requires the Company to make estimates and judgments because most of the removal obligations are many years in the future and contracts and regulation often have vague descriptions of what constitutes removal. Asset removal technologies and cost are constantly changing, as are regulatory, political, environmental, safety and public relations considerations. Pursuant to the accounting guidance relating to "Assets Retirement Obligations", the Company is required to record a separate liability for the estimated fair value of its asset retirement obligations, with an offsetting increase to the related oil and natural gas properties representing asset retirement costs on its balance sheet. The cost of the related oil and natural gas asset, including the asset retirement cost, is depreciated over the useful life of the asset. The estimated fair value of asset retirement obligations is measured by reference to the expected future cash outflows required to satisfy the retirement obligation discounted at the Company's credit-adjusted risk-free interest rate. Accretion expense is recognized over time as the discounted liability is accreted to its expected settlement value.
	Inherent to the present value calculation are numerous estimates, assumptions and judgments, including the ultimate settlement amounts, inflation factors, credit adjusted risk-free rates, timing of settlement and changes in the legal, regulatory, environmental and political environments. To the extent future revisions to these assumptions impact the present value of the abandonment liability, the Company will make corresponding adjustments to both the asset retirement obligation and the related oil and natural gas property asset balance. Increases in the discounted abandonment liability and related oil and natural gas assets resulting from the passage of time will be reflected as additional accretion and depreciation expense in the consolidated statements of operations.
	Inventory
	Inventories consist of various tubular products that are used in the Company's drilling programs. The products are stated at the average cost. Cost is determined using a weighted average method comprised of the purchase price and other directly attributable costs.
	Income Taxes
	The Company applied the liability method of accounting for income taxes in accordance with accounting guidance related to "Income Taxes" as clarified by "Accounting for Uncertainty in Income Taxes." Under this method, deferred tax assets and liabilities are determined by applying tax rates in effect at the end of a reporting period to the cumulative temporary differences between the tax bases of assets and liabilities and their reported amounts in the financial statements. Since the Company is in development stage and there can be no assurance that the Company will generate any earnings or any specific level of earnings in future years, the Company has established a valuation allowance that equals its net deferred tax assets. See Note 17.
	Equity-Based Compensation
	The Company accounts for stock-based compensation at fair value. The Company grants various types of stock-based awards including stock options, restricted stock and performance-based awards. The fair value of stock option awards is determined using the Black-Scholes-Merton option-pricing model. For restricted stock awards with market conditions, the fair value of the awards is measured using the asset-or-nothing option pricing model. Restricted stock awards without market conditions and the performance-based awards are valued using the market price of the Company's common stock on the grant date. The Company records compensation cost, net of estimated forfeitures, on a straight-line basis for stock-based compensation awards over the requisite service period except for performance-based awards. For performance-based awards, compensation cost is recognized over the requisite service period as and when the Company determines that the achievement of the performance condition is probable, using the per-share fair value measured at grant date. See Note 15.
	Earnings (Loss) Per Share
	Basic income (loss) per share was calculated by dividing net income or loss applicable to common shares by the weighted average number of common shares outstanding during the periods presented. The calculation of diluted income (loss) per share should include the potential dilutive impact of non-vested restricted shares, non-vested restricted stock units, outstanding stock options and the Company's 2.625% convertible senior notes due 2019, during the period, unless their effect is anti-dilutive. For the year ended December 31, 2013, 6,735,046 shares of non-vested restricted stock, non-vested restricted stock units, outstanding stock options and 2.625% convertible senior notes due 2019, were excluded from the diluted income (loss) per share because they are anti-dilutive. For the year ended December 31, 2012, 5,617,697 shares of non-vested restricted stock, non-vested restricted stock units and outstanding stock options were excluded from the diluted income (loss) per share because they are anti-dilutive.
	Operating Costs and Expenses
	Expenses consist primarily of the costs of acquiring and processing of geological and geophysical data, exploration and appraisal drilling expenses, consultants, telecommunications, payroll and benefit costs, information system and legal costs, office rent, contract costs, and bookkeeping and audit fees.

Cash_and_Cash_Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2013
Cash and Cash Equivalents	'
Cash and Cash Equivalents	'
	3. Cash and Cash Equivalents
	As of December 31, 2013 and 2012, cash and cash equivalents consisted of the following:
		December 31,
		2013		2012
		(in thousands)
	Cash at banks	$	82,428	$	65,935
	Money market funds		75,039		1,105,148
	Held-to-maturity securities(1)		34,993		254,732
		$	192,460	$	1,425,815
	-1
	These securities mature three months or less from date of purchase.

Restricted_Funds

Restricted Funds	12 Months Ended
	Dec. 31, 2013
Restricted Funds	'
Restricted Funds	'
	4. Restricted Funds
	Restricted funds consisted of the following:
		December 31,
		2013		2012
		(in thousands)
	Short-term:
	Collateral on Letters of Credit for Angola(1)	$	200,339	$	—
	Ensco 8503 escrow account(2)		—		90,440
		$	200,339	$	90,440
	Long-term:
	Ensco 8503 escrow account(2)		—		90,440
	Collateral on Letters of Credit for Angola(1)		104,496		304,492
	Other vendor restricted deposits		—		720
		$	104,496	$	395,652
	-1
	As of December 31, 2013 and December 31, 2012, $304.8 million and $304.5 million, respectively, was held in a collateral account established to secure letters of credit issued in support of the Company's contractually agreed work program obligations on Blocks 9, 20 and 21 offshore Angola. As of December 31, 2013, the collateral in this account was invested in U.S. Treasury bills and Treasury notes purchased at discounts and at premiums, respectively, resulting in a net carrying value of $304.8 million. The contractual maturities of these securities are within one year. The $200.3 million classified as short-term restricted funds at December 31, 2013 includes $153.6 million of cash collateral associated with work program obligations which have been completed for Blocks 20 and 21 and for which the Company expects to receive distribution of the collateral in 2014. The remaining $46.7 million secures work program obligations of $45.3 million for Block 9 for which the initial exploration phase expires on March 1, 2014, if not extended.
	-2
	As of December 31, 2012, $180.9 million was held in an escrow account established in December 2009 as a guarantee of performance to Ensco Offshore Company ("Ensco") for the Ensco 8503 drilling rig contract. As of December 31, 2013 the escrow account balance was refunded to the Company pursuant to the terms of the drilling rig contract. The drilling rig contract expired in January 2014.

Joint_Interests_and_Other_Rece

Joint Interests and Other Receivables	12 Months Ended
	Dec. 31, 2013
Joint Interests and Other Receivables	'
Joint Interests and Other Receivables	'
	5. Joint Interests and Other Receivables
	As of December 31, 2013 and 2012, the balance in joint interest and other receivables consisted of the following:
		December 31,
		2013		2012
		(in thousands)
	Partners in the U.S. Gulf of Mexico	$	68,664	$	52,439
	Partners in West Africa(1)		46,897		2,185
	Accrued interest on investment securities		5,632		3,647
	Other		3,446		3,321
		$	124,639	$	61,592
	-1
	The amount of $46.9 million as of December 31, 2013 includes $15.7 million related to the Company's partners on Block 20 offshore Angola and $31.2 million related to the outstanding balance due from the Company's partners on Blocks 9 and 21 offshore Angola, a portion of which is currently past due but the Company expects to recover.

Prepaid_Expenses_and_Other_Cur

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2013
Prepaid Expenses and Other Current Assets	'
Prepaid Expenses and Other Current Assets	'
	6. Prepaid Expenses and Other Current Assets
	As of December 31, 2013 and 2012, prepaid expenses and other current assets consisted of the following:
		December 31,
		2013		2012
		(in thousands)
	Prepaid expenses:
	Prepaid expenses(1)	$	37,796	$	11,729
	Other current assets:
	Cash advance to joint venture partner(2)		9,685		351
	Rig mobilization, regulatory and other related costs(3)		8,376		11,861
		$	55,857	$	23,941
	-1
	As of December 31, 2013, prepaid expenses include $11.5 million of the prepaid and unamortized portion of payments made for software licenses, related maintenance fees, insurance and $26.3 million of prepaid costs associated with the Ensco drilling rig contract. The drilling rig contract terminated in January 2014 and upon receipt and application of prepaid amounts against the final invoice from Ensco, any remaining balance of the prepayment will be refunded to the Company. As of December 31, 2012, the $11.7 million in prepaid expenses consisted of the prepaid and unamortized portion of payments made for software licenses, related maintenance fees and insurance.
	-2
	As of December 31, 2013, the $9.7 million in other current assets relates to payment of cash calls made to our joint interest partner, Total Gabon, for operating costs to drill the Diaman #1B exploration well. This prepayment will be applied against the joint interest bills upon receipt from Total Gabon.
	-3
	As of December 31, 2013, the $8.4 million in other current assets relates to the short-term portion of the mobilization and regulatory acceptance testing costs associated with the SSV Catarina drilling rig. As of December 31, 2012, the $11.9 million in other current assets relates to the remaining balance of the mobilization and equipment upgrade costs associated with the Ensco 8503 drilling rig. These costs are amortized on a straight-line basis over the terms of the respective drilling contracts.

Investments

Investments	12 Months Ended
	Dec. 31, 2013
Investments	'
Investments	'
	7. Investments
	The Company's investments in held-to-maturity securities which are recorded at amortized cost and approximate fair market value were as follows at December 31, 2013 and 2012:
		December 31,
		2013		2012
		(in thousands)
	U.S. Treasury securities	$	304,834	$	483,775
	Corporate securities		856,002		510,691
	Commercial paper		408,033		562,975
	Certificates of deposit		105,000		7,000
	Total	$	1,673,869	$	1,564,441
	The Company's held-to-maturity securities were included in the following captions in the Company's balance sheets:
		December 31,
		2013		2012
		(in thousands)
	Cash and cash equivalents	$	34,993	$	254,732
	Short-term investments		1,319,380		789,668
	Short-term restricted funds		200,339		90,440
	Long-term restricted funds		104,496		393,334
	Long-term investments		14,661		36,267
		$	1,673,869	$	1,564,441
	The contractual maturities of these held-to-maturity securities at December 31, 2013 and 2012 were as follows:
		December 31,
		2013				2012
		Amortized		Estimated Fair		Amortized		Estimated Fair
		Cost		Value		Cost		Value
		($ in thousands)
	Within 1 year	$	1,659,208	$	1,659,208	$	1,528,174	$	1,528,174
	After 1 year		14,661		14,661		36,267		36,267
		$	1,673,869	$	1,673,869	$	1,564,441	$	1,564,441

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2013
Fair Value Measurements	'
Fair Value Measurements	'
	8. Fair Value Measurements
	The following tables summarize the Company's significant financial instruments as categorized by the fair value measurement hierarchy:
		Level 1				Level 2
		Carrying		Fair		Carrying		Fair		Balance as of
		Value		Value(1)		Value		Value(1)		December 31,
										2013
		($ in thousands)
	Cash and cash equivalents:
	Cash	$	82,428	$	82,428	$	—	$	—	$	82,428
	Money market funds		75,039		75,039		—		—		75,039
	Commercial paper		—		—		9,993		9,993		9,993
	Certificate of deposits						25,000		25,000		25,000
	Subtotal		157,467		157,467		34,993		34,993		192,460
	Short-term restricted funds:
	U.S. Treasury notes		—		—		200,339		200,339		200,339
	Subtotal		—		—		200,339		200,339		200,339
	Short-term investments:
	Corporate bonds		—		—		848,307		848,307		848,307
	Commercial paper		—		—		391,073		391,073		391,073
	Certificates of deposits		—		—		80,000		80,000		80,000
	Subtotal		—		—		1,319,380		1,319,380		1,319,380
	Long-term restricted funds:
	U.S. Treasury notes		—		—		104,496		104,496		104,496
	Subtotal		—		—		104,496		104,496		104,496
	Long-term investments:
	Commercial paper		—		—		6,967		6,967		6,967
	Corporate bonds		—		—		7,694		7,694		7,694
	Subtotal		—		—		14,661		14,661		14,661
	Total	$	157,467	$	157,467	$	1,673,869	$	1,673,869	$	1,831,336
		Level 1				Level 2
										Balance as of
										December 31,
		Carrying Value		Fair Value(1)		Carrying Value		Fair Value(1)		2012
		($ in Thousands)
	Cash and cash equivalents:
	Cash	$	65,935	$	65,935	$	—	$	—	$	65,935
	Money market funds		1,105,148		1,105,148		—		—		1,105,148
	Commercial paper		—		—		247,206		247,206		247,206
	Corporate bonds		—		—		7,526		7,526		7,526
	Subtotal		1,171,083		1,171,083		254,732		254,732		1,425,815
	Short-term restricted funds:
	U.S. Treasury bills		—		—		90,440		90,440		90,440
	Subtotal		—		—		90,440		90,440		90,440
	Short-term investments:
	Corporate bonds		—		—		466,898		466,898		466,898
	Commercial paper		—		—		315,769		315,769		315,769
	Certificate of deposits		—		—		7,001		7,001		7,001
	Subtotal		—		—		789,668		789,668		789,668
	Long-term restricted funds:
	Money market funds		2,318		2,318		—		—		2,318
	U.S. Treasury bills		—		—		178,216		178,216		178,216
	U.S. Treasury notes		—		—		215,118		215,118		215,118
	Subtotal		2,318		2,318		393,334		393,334		395,652
	Long-term investments:
	Corporate bonds		—		—		36,267		36,267		36,267
	Subtotal		—		—		36,267		36,267		36,267
	Total	$	1,173,401	$	1,173,401	$	1,564,441	$	1,564,441	$	2,737,842
	-1
	As of December 31, 2013 and 2012, the Company did not record any OTTI on these assets.

Property_Plant_and_Equipment

Property, Plant, and Equipment	12 Months Ended
	Dec. 31, 2013
Property, Plant, and Equipment	'
Property, Plant, and Equipment	'
	9. Property, Plant, and Equipment
	Property, plant, and equipment is stated at cost less accumulated depreciation/amortization and consisted of the following:
				December 31,
		Estimated
		Useful Life
		(Years)		2013			2012
				($ in thousands)
	Oil and Gas Properties:
	Proved properties:
	Well and development costs			$	92,579		$	—
	Total proved properties				92,579			—
	Unproved properties:
	Oil and gas leasehold			$	754,894		$	721,853
	Less: accumulated valuation allowance				(160,913	)		(78,413	)
					593,981			643,440
	Exploration wells in process				777,823			451,024
	Total unproved properties				1,371,804			1,094,464
	Total oil and gas properties, net				1,464,383			1,094,464
	Other Property and Equipment:
	Computer equipment and software	3			5,115			3,166
	Office equipment and furniture	3 - 5			2,132			2,093
	Vehicles	3			265			268
	Leasehold improvements	3 - 10			2,456			2,298
	Running tools and equipment	3			6,318			—
					16,286			7,825
	Less: accumulated depreciation and amortization(1)				(4,394	)		(2,533	)
	Total other property and equipment, net				11,892			5,292
	Property, plant, and equipment, net			$	1,476,275		$	1,099,756
	-1
	During the year ended December 31, 2012, the Company wrote off $2.2 million of old computer equipment and leasehold improvements which were fully depreciated and therefore had no impact on the consolidated statements of operations and consolidated statements of cash flow.
	The Company recorded $1.9 million, $1.2 million and $0.7 million of depreciation and amortization expense for the years ended December 31, 2013, 2012 and 2011, respectively, and $6.6 million for the period November 10, 2005 (inception) through December 31, 2013, respectively.
	Proved Oil and Gas Properties
	The Heidelberg project was formally sanctioned for development in mid-2013. As a result of the project sanction, the Company reclassified its Heidelberg exploration well costs to proved property well and development costs and these costs will be amortized when the related proved developed reserves are produced. As of December 31, 2013, the well and development costs consist of $31.6 million relating to exploration well costs for the Heidelberg #1 exploration well and Heidelberg #3 appraisal well and $61.0 million for costs associated with well development.
	Unproved Oil and Gas Properties
	On December 20, 2011, the Company acquired a 40% working interest in Block 20 offshore Angola for a total consideration of $347.1 million, of which $337.1 million is contractually scheduled to be paid over five years commencing in January 2012. As of December 31, 2013, out of the $337.1 million, $165.7 million has been paid and the remaining $171.4 million was accrued in short-term and long-term contractual obligations. See Note 12—Contractual Obligations. In addition to the Block 20 interests, the Company has $10.8 million of unproved property acquisition costs relating to its 40% interests in Blocks 9 and 21 offshore Angola and its 21.25% working interest in the Diaba Block offshore Gabon.
	As of December 31, 2013, the Company also has $236.1 million of unproved property acquisition costs, net of valuation allowance for impairment, relating to its U.S. Gulf of Mexico properties. On February 26, 2013, the Company executed a Purchase and Sale agreement (the "PSA") to sell its ownership interests on an unproved oil and gas property on Mississippi Canyon Block 209 for a total consideration of $5.6 million. The Company received $1.5 million at closing and an additional $1.5 million in September 2013 when the buyer commenced operations on the property. Pursuant to the terms and conditions of the PSA, the Company will receive the remaining $2.6 million contingent upon the purchaser's commencement of production on this property in the future. For the year ended December 31, 2013, the Company recognized a gain of $3.0 million on the sale of assets as a result of this transaction. During the year ended December 31, 2013, the Company paid a total consideration of $37.6 million for acquisition of ownership interests in unproved oil and gas properties on Garden Banks Block 822, Mississippi Canyon Block 605 and Walker Ridge Block 232 in the U.S. Gulf of Mexico.
	As of December 31, 2013 and December 31, 2012, the Company has a net total of $594.0 million and $643.4 million, respectively, of unproved property acquisition costs on the consolidated balance sheets.
	Acquisition costs of unproved properties are assessed for impairment during the holding period and transferred to proved oil and gas properties to the extent associated with successful exploration activities. There are no impairment indicators to date that would require the Company to impair the unproved properties in Blocks 20 and 21 offshore Angola and in the Diaba Block offshore Gabon. For the unproved properties associated with Block 9 offshore Angola, the initial exploration phase expires on March 1, 2014 under the Risk Service Agreement for Block 9. The Company has requested an extension of the initial exploration phase and such extension is pending approval by Sonangol and the Angola Ministry of Petroleum. If the extension is not approved, the Company will forfeit its acreage on Block 9, impair the $2.5 million paid for its working interest in Block 9 and may have to relinquish $45.3 million that secures work program obligations on Block 9. Oil and gas leases for unproved properties in the U.S. Gulf of Mexico with a carrying value greater than $1.0 million are assessed individually for impairment based on the Company's current exploration plans and an allowance for impairment is provided if impairment is indicated. Leases that are individually less than $1.0 million in carrying value or are near expiration are amortized on a group basis over the average terms of the leases at rates that provide for full amortization of leases upon lease expiration. These leases have expiration dates ranging from 2014 through 2022. As of December 31, 2013 and 2012, the balance for unproved properties that were subject to amortization before impairment provision was $68.9 million and $69.1 million, respectively. The Company recorded a lease impairment allowance of $87.0 million, $60.2 million and $9.1 million for the years ended December 31, 2013, 2012 and 2011, respectively, and $165.6 million for the period November 10, 2005 (inception) through December 31, 2013.
	Capitalized Exploration Well Costs
	If an exploration well provides evidence as to the existence of sufficient quantities of hydrocarbons to justify potential completion as a producing well, drilling costs associated with the well are initially capitalized, or suspended, pending a determination as to whether a commercially sufficient quantity of proved reserves can be attributed to the area as a result of drilling. This determination may take longer than one year in certain areas (generally, deepwater and international locations) depending upon, among other things, (i) the amount of hydrocarbons discovered, (ii) the outcome of planned geological and engineering studies, (iii) the need for additional appraisal drilling activities to determine whether the discovery is sufficient to support an economic development plan and (iv) the requirement for government sanctioning in international locations before proceeding with development activities.
	The following tables reflect the Company's net changes in and the cumulative costs of capitalized exploration well costs (excluding any related leasehold costs):
		December 31,			December 31,			December 31,
		2013			2012			2011
		($ in thousands)
	Beginning of period	$	451,024		$	178,338		$	106,881
	Additions to capitalized exploration
	U.S. Gulf of Mexico:
	Exploration well costs		154,877			178,295			11,214
	Capitalized interest		3,928			—			—
	West Africa:
	Exploration well costs		457,608			168,309			96,849
	Capitalized interest		12,271			—			—
	Reclassifications to wells, facilities, and equipment based on determination of proved reserves		(38,446	)		—			—
	Amounts charged to expense(1)		(263,439	)		(73,918	)		(36,606	)
	End of period	$	777,823		$	451,024		$	178,338
	-1
	The amount of $263.4 million for the year ended December 31, 2013 represents $120.0 million of impairment charges on exploration wells drilled in the U.S. Gulf of Mexico which did not encounter commercial hydrocarbons, $126.3 million of impairment charges on exploration wells drilled offshore Angola which failed to flow measurable hydrocarbons from drill stem tests and a portion of the cost of exploration wells drilled offshore Angola that were determined to have no utility in the lowest interval beneath the pay zone and $17.1 million of impairment charges on the exploration well drilled offshore Gabon which needed to be re-spud due to mechanical problems with the wellbore. The amount of $73.9 million for the year ended December 31, 2012 represents impairment charges on exploration wells drilled in the U.S. Gulf of Mexico which did not encounter commercial hydrocarbons.
		December 31,			December 31,
		2013			2012
		($ in thousands)
	Cumulative costs:
	U.S. Gulf of Mexico
	Exploration well costs	$	204,707		$	208,275
Capitalized interest		3,928			—
West Africa
Exploration well costs		556,917			242,749
Capitalized interest		12,271			—
	$	777,823		$	451,024
Well costs capitalized for a period greater than one year after completion of drilling (included in table above)	$	399,775		$	194,853
As of December 31, 2013, capitalized exploration well costs that have been suspended longer than one year are associated with the Company's Shenandoah, North Platte and Cameia discoveries. These well costs are suspended pending ongoing evaluation including, but not limited to, results of additional appraisal drilling, well-test analysis, additional geological and geophysical data and approval of a development plan. Management believes these discoveries exhibit sufficient indications of hydrocarbons to justify potential development and is actively pursuing efforts to fully assess them. If additional information becomes available that raises substantial doubt as to the economic or operational viability of these discoveries, the associated costs will be expensed at that time. The Heidelberg discovery has been sanctioned for development and the Heidelberg capitalized exploration and appraisal well costs were reclassified to development costs as of December 31, 2013.

Other_Assets

Other Assets	12 Months Ended
	Dec. 31, 2013
Other Assets	'
Other Assets	'
	10. Other Assets
	As of December 31, 2013 and 2012, the balance in other assets consisted of the following:
		December 31,
		2013		2012
		(in thousands)
	Debt issue cost(1)	$	20,983	$	23,042
	Long-term portion of prepaid shorebase leases		3,241		—
	Rig mobilization costs(2)		11,153		—
	Long-term accounts receivable(3)		17,923		—
	Other		437		—
		$	53,737	$	23,042
	-1
	As of December 31, 2013 and 2012, the $21.0 million and $23.0 million in debt issue cost relate to the issuance of the Company's 2.625% convertible senior notes due 2019, as described in Note 11, and which are amortized over the life of the notes using the effective interest method.
	-2
	The $11.2 million as of December 31, 2013 relates to costs associated with the long-term mobilization and the regulatory acceptance testing of the SSV Catarina drilling rig. These costs are amortized over the term of the drilling rig contract.
	-3
	On March 16, 2012, Angola enacted Presidential Decree No. 3/12, which, among other things, provided that Angolan private petroleum companies are exempt from any requirement to carry Sonangol P&P. As a result of this statute, one of the Company's partners in Angola has taken the position that it is no longer required to pay a 3.75% cost interest attributable to Sonangol P&P's share of expenses. As of December 31, 2013, these expenditures totaled approximately $17.9 million, which is classified as a long term receivable as the Company expects this amount to be recovered pursuant to the terms of the Risk Services Agreements governing Blocks 9 and 21.

Longterm_Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2013
Long-term Debt	'
Long-term Debt	'
	11. Long-term Debt
	On December 17, 2012, the Company issued $1.38 billion aggregate principal amount of its 2.625% convertible senior notes due 2019 (the "Notes"). The Notes are the Company's senior unsecured obligations and interest is payable semi-annually in arrears on June 1 and December 1 of each year. For the year ended December 31, 2013, the Company paid $34.6 million in interest on the notes. The Notes will mature on December 1, 2019, unless earlier repurchased or converted in accordance with the terms of the Notes. The Notes may be converted at the option of the holder at any time prior to 5:00 p.m., New York City time, on the second scheduled trading day immediately preceding the maturity date, in multiples of $1,000 principal amount. The Notes are convertible at an initial conversion rate of 28.023 shares of common stock per $1,000 principal amount, representing an initial conversion price of approximately $35.68 per share for a total of approximately 38.7 million underlying shares. The conversion rate is subject to adjustment upon the occurrence of certain events, as defined in the indenture governing the Notes, but will not be adjusted for any accrued and unpaid interest except in limited circumstances. Upon conversion, the Company's conversion obligation may be satisfied, at the Company's option, in cash, shares of common stock or a combination of cash and shares of common stock.
	Holders of the Notes who convert their Notes in connection with a "make-whole fundamental change", as defined in the indenture governing the Notes, may be entitled to a make-whole premium in the form of an increase in the conversion rate. Additionally, in the event of a fundamental change, as defined in the indenture governing the Notes, holders of the Notes may require the Company to repurchase for cash all or a portion of their Notes equal to $1,000 or a multiple of $1,000 at a fundamental change repurchase price equal to 100% of the principal amount of Notes, plus accrued and unpaid interest, if any, to, but not including, the fundamental change repurchase date.
	Upon the occurrence of an Event of Default, as defined within the Indenture governing the Notes, the Trustee or the Holders of at least 25% in aggregate principal amount of the Notes then outstanding may declare 100% of the principal of, and accrued and unpaid interest on, all the Notes to be due and payable immediately.
	In accordance with accounting guidance relating to, "Debt with Conversion and Other Options", the Company separately accounts for the liability and equity conversion components of the Notes due to the Company's option to settle the conversion obligation in cash. The fair value of the debt excluding the conversion feature at the date of issuance was estimated to be approximately $989.5 million and was calculated based on the fair value of similar non-convertible debt instruments. The resulting value of the conversion option of $390.5 million was recognized as a debt discount and recorded as additional paid-in capital on the Company's consolidated balance sheets. Total debt issue cost on the Notes was $32.2 million of which $23.1 million was allocated to the liability component of the Notes and $9.1 million to the equity component of the Notes. The debt discount and the liability component of the debt issue costs are amortized over the term of the Notes. The effective interest rate used to amortize the debt discount and the liability component of the debt issue costs was approximately 8.40% based on the Company's estimated non-convertible borrowing rate as of the date the Notes were issued. Since the Company incurred losses for all periods, the impact of the conversion option would be anti-dilutive to the earnings per share and therefore was not included in the calculation.
	The carrying amounts of the liability components of the Notes were as follows:
		December 31, 2013								December 31, 2012
		Principal			Unamortized			Carrying		Principal		Unamortized			Carrying
		Amount			discount(1)			Amount		Amount		discount			Amount
		($ in thousands)
	Carrying amount of liability component
	2.625% convertible senior notes due 2019	$	1,380,000		$	(344,020	)	$	1,035,980	$	1,380,000	$	(388,809	)	$	991,191
	-1
	Unamortized discount will be amortized over the remaining life of the Notes which is 6 years.
	The carrying amounts of the equity components of the Notes were as follows:
		December 31,			December 31,
		2013			2012
		($ in thousands)
	Debt discount relating to value of conversion option	$	390,540		$	390,540
	Debt issue costs		(9,124	)		(9,124	)
	Total	$	381,416		$	381,416
	Fair Value The fair value of the Notes excluding the conversion feature was $1,227.1 million and $989.5 million as of December 31, 2013 and 2012, respectively, and was calculated based on the fair value of similar non-convertible debt instruments (level 2) since an observable quoted price of the Notes or a similar asset or liability is not readily available.
	Interest expense associated with the 2.625% convertible senior notes due 2019 was as follows:
										For the Period
										November 10, 2005
										(Inception)
		For Year Ended December 31,								through
		2013			2012			2011		December 31, 2013
		($ in thousands)
	Interest expense associated with accrued interest(1)	$	18,529		$	1,294		$	—	$	19,823
	Interest expense associated with accretion of debt discount		44,789			1,843			—		46,632
	Interest expense associated with amortization of debt issue costs		2,058			75			—		2,133
	Total	$	65,376		$	3,212		$	—	$	68,588
	-1
	The $18.5 million and $1.3 million for the years ended December 31, 2013 and 2012, respectively, represent interest expense net of capitalized amounts of $17.7 million and $0 million, respectively.

Contractual_Obligations

Contractual Obligations	12 Months Ended
	Dec. 31, 2013
Contractual Obligations	'
Contractual Obligations	'
	12. Contractual Obligations
	The short-term and long-term contractual obligations consist of the following:
		December 31,
		2013		2012
		($ in thousands)
	Short-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	150	$	150
	Social obligation payments for Block 21, offshore Angola		300		300
	Social obligation and bonus payments for Block 20, offshore Angola(1)(2)		48,569		48,569
		$	49,019	$	49,019
	Long-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	669	$	848
	Social obligation payments for Block 21, offshore Angola		1,381		1,684
	Social obligation and bonus payments for Block 20, offshore Angola(2)		122,851		165,706
		$	124,901	$	168,238
	-1
	$42.9 million of this amount was paid in January 2014.
	-2
	The total amount of social obligation payments for Block 20 has been capitalized. See Note 9.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Stockholders' Equity	'
Stockholders' Equity	'
	13. Stockholders' Equity
	On January 15, 2012, the Company withheld the issuance of an aggregate amount of 9,127 shares of its common stock, at a price of $18.74 per share, to satisfy tax withholding obligations of certain of its officers that arose upon the distribution of deferred stock compensation.
	On February 29, 2012, the Company issued 18,050,000 shares of common stock at a public offering price of $28.00 per share.
	On December 17, 2012, the Company issued $1.38 billion aggregate principal amount of its 2.625% convertible senior notes due 2019. As of December 31, 2013 and 2012, $381.4 million was recorded as the equity component of the Notes. See also Note 11—Long-term Debt.

Seismic_and_Exploration_Expens

Seismic and Exploration Expenses	12 Months Ended
	Dec. 31, 2013
Seismic and Exploration Expenses	'
Seismic and Exploration Expenses	'
	14. Seismic and Exploration Expenses
	Seismic and exploration expenses consisted of the following:
								For the Period
								November 10, 2005
								(Inception)
		For Year Ended December 31,						through
		2013		2012		2011		December 31, 2013
		($ in thousands)
	Seismic costs	$	63,721	$	42,447	$	20,443	$	405,769
	Seismic cost recovery(1)		—		—		—		(25,126	)
	Leasehold delay rentals		6,660		6,383		6,075		39,562
	Force Majeure expense(2)		—		—		—		13,549
	Drilling rig expense		3,832		12,753		5,721		30,631
		$	74,213	$	61,583	$	32,239	$	464,385
	-1
	These amounts represent reimbursement from partners of past seismic costs incurred by the Company.
	-2
	These amounts represent expenditures resulting from suspension of drilling activities in the U.S. Gulf of Mexico as a result of the explosion and sinking of the Deepwater Horizon drilling rig in the U.S. Gulf of Mexico, the resulting oil spill and the regulatory response thereto and other exploration expenses.

Equity_based_Compensation

Equity based Compensation	12 Months Ended
	Dec. 31, 2013
Equity based Compensation	'
Equity based Compensation	'
	15. Equity based Compensation
	Overview.    Under the Company's Long Term Incentive Plan (the "Incentive Plan"), the Company may issue stock options, stock appreciation rights, restricted stock, restricted stock units, performance awards and other stock-based awards to employees. At December 31, 2013, approximately 7.5 million shares remain available for grant under the Incentive Plan.
	On January 28, 2010, the Company adopted the Non-Employee Directors Compensation Plan (the "NED Plan"). Under the NED Plan, the Company may issue options, restricted stock units, other stock-based award or retainers to non-employee directors. At December 31, 2013, 500,158 shares remain available for grant under the NED Plan.
	In accordance with ASC No. 718, Compensation—Stock Compensation, the Company recognizes compensation cost for equity-based compensation to employees and non-employee directors over the period during which the recipient is required to provide service in exchange for the award, based on the fair value of the equity instrument on the date of grant, net of estimated forfeitures. If actual forfeitures differ from the Company's estimates, additional adjustments to compensation expense will be required in future periods.
	Restricted Stock.    The Company accounted for the restricted stock based on ASC Topic 718 as described above. For restricted stock awards with market conditions, the fair value of the awards is measured using the asset-or-nothing option pricing model. Restricted stock awards without market conditions and the performance-based awards are valued using the market price of the Company's common stock on the grant date. The Company records compensation cost, net of estimated forfeitures, for stock-based compensation awards over the requisite service period except for performance-based awards. For performance-based awards, compensation cost is recognized over the requisite service period as and when the Company determines that the achievement of the performance condition is probable, using the per-share fair value measured at grant date.
	The following table summarizes the information about the restricted stock awarded to employees for each of the three years in the period ended December 31, 2013:
		Years Ended December 31,
		2013					2012					2011
		Restricted			Weighted		Restricted			Weighted		Restricted			Weighted
		Shares			Average		Shares			Average		Shares			Average
					Grant Date					Grant Date					Grant Date
					Fair Value					Fair Value					Fair Value
					Per Share					Per Share					Per Share
	Non-vested shares at beginning of year		4,040,825		$	13.05		4,599,783		$	11.27		5,570,895		$	9.77
	Granted		620,840		$	24.58		487,710		$	26.01		214,792		$	8.54
	Vested		(239,317	)	$	17.37		(738,628	)	$	13.05		(1,185,904	)	$	3.75
	Forfeited or expired		(87,462	)	$	20.91		(308,040	)	$	12.17		—			—
	Non-vested shares at end of year		4,334,886		$	14.31		4,040,825		$	13.05		4,599,783		$	11.27
	Weighted-average vesting period remaining		1.22 years					1.87 years					2.5 years
	Unrecognized compensation ($ in thousands)	$	22,467				$	23,827				$	29,559
	A total of 39,818 restricted stock unit awards were granted to non-employee directors during the year ended December 31, 2013 for annual retainers. As of December 31, 2013, the Company has granted a cumulative total of 177,763 restricted stock units to non-employee directors. For the year ended December 31, 2013 and 2012, the Company also granted 15,318 and 12,221 shares of common stock, respectively, as retainer awards to non-employee directors who elected to be compensated by stock in lieu of cash payments. The weighted average fair value of these shares at grant date was $25.40 per share.
	Non-Qualified Stock Options.    The Company grants non-qualified stock options to employees at an exercise price equal to the market value of the Company's common stock on the grant date. The non-qualified stock option awards have contractual terms of 10 years. The options granted in December 2010 vest ratably over a four-year period from date of grant, the options granted in February 2012 cliff vest on December 31, 2014 and the options granted in February 2013 vest 50% on December 31, 2015 and 50% on December 31, 2016.
	The fair value of each stock option granted is determined using the Black-Scholes-Merton option-pricing model based on several assumptions. These assumptions are based on management's best estimate at the time of grant. The Company used the following the weighted average of each assumption based on the grants in 2013:
		2013
	Expected Term in Years		6.68
	Expected Volatility		61.58	%
	Expected Dividends		0	%
	Risk-Free Interest Rate		1.28	%
	The Company estimates expected volatility based on an analysis of its stock price since the IPO and comparing the stock price volatility for the period from IPO date through December 31, 2013 with the historical stock price volatility of a similar exploration and production company. The Company estimates the expected term of its option awards based on the vesting period and average remaining contractual term, referred to as the "simplified method". The Company uses this method to provide a reasonable basis for estimating its expected term based on a lack of sufficient historical employee exercise data on stock option awards.
	A summary of the stock options activities for the year ended December 31, 2013 is presented below:
		Shares			Weighted		Weighted-Average			Aggregate
					Average		Remaining			Intrinsic Value
					Exercise		Contractual Term			(thousands)
					Price		(years)
	Outstanding at January 1, 2013		1,434,393		$	17.87		8.3		$	12,158
	Granted		959,023		$	23.78		9.1
	Exercised		(13,985	)	$	12.45		6.9		$	219
	Forfeited or expired		(40,713	)	$	22.89
	Outstanding at December 31, 2013		2,338,718		$	20.24		8		$	3,937
	Vested or expected to vest at December 31, 2013		1,568,748		$	23.83		8.5		$	965
	Exercisable at December 31, 2013		737,973		$	12.45		6.9		$	2,952
	The weighted-average grant-date fair value of stock options granted during 2013 and 2012 was $14.08 and $17.92 per option, respectively, using the Black-Scholes option-pricing model. As of December 31, 2013, $14.0 million of total unrecognized compensation cost related to stock option is expected to be recognized over a weighted-average period of 2.15 years.
	Restricted Stock Units.    On December 3, 2010, the Company granted 198,838 restricted stock units to employees based on the Restricted Stock Unit (RSU) Award Agreement. Under the RSU Award Agreement the share-based payment is earned based on the number of successful wells drilled during the three year period ending December 31, 2013. The RSU award will vest within a range of 0% to 200% of the number of RSU shares awarded on scheduled vesting dates contingent upon the recipient's continued service at each vesting date and based on the achievement of successful wells drilled as defined in the RSU Award Agreement. In no event shall the recipients vest in an amount greater than 200% of the Award or in aggregate 397,676 RSU shares. The percentage of the RSU awards vested at each of the three year periods ending December 31, 2013 is calculated by the number of successful wells drilled during the respective years multiplied by vesting percentage ranging from 25% to 37.5%. The RSU Award Agreement therefore has multiple implicit service periods which are determined by and when the Company drills a successful well. The fair value of the RSUs at grant date was $12.45 per share. However, on February 24, 2012, the Company amended certain terms and conditions of its RSU award agreement which resulted in the Company using the fair value of $30.50 per share at modification date to recognize the equity based compensation expense for the RSUs that vested during 2012 and 2013.
	A summary of the restricted stock units activities for the year ended December 31, 2013 is presented below:
		Years Ended December 31,
		2013					2012					2011
		Number of			Weighted		Number of			Weighted		Number of			Weighted
		shares			Average		shares			Average		shares			Average
		relating			Grant Date		relating			Grant Date		relating			Grant Date
		Restricted			Fair Value		Restricted			Fair Value		Restricted			Fair Value
		Stock Units			Per Unit		Stock Units			Per Unit		Stock Units			Per Unit
	Non-vested at beginning of year		109,275		$	30.5		198,838		$	12.45		198,838		$	12.45
	Granted		—			—		—			—		—			—
	Vested		(87,401	)	$	30.5		(74,537	)	$	30.5		—			—
	Forfeited or expired		(250	)	$	30.5		(15,026	)	$	30.5		—			—
	Non-vested at end of year(1)		21,624		$	30.5		109,275		$	30.5		198,838		$	12.45
	Weighted-average period remaining		—					1 year					2 years
	-1
	For the year ended December 31, 2013, the Company recognized $4.6 million in stock compensation expenses for a probable vesting of 129,611 RSU shares during the first quarter of 2014 based on the performance target achieved from the success of three exploration wells drilled in 2013. The vesting of 129,611 RSU shares in 2014 will exceed the total outstanding RSUs of 21,624 at December 31, 2013 as reported in the above table due to the aggregate payout of 162.5% of the target amount of 198,838 RSUs since inception. Payouts of 37.5%, 50% and 75% of the target amount were approved by the Company's board of directors for each of the three years in the period ended December 31, 2013, totaling 162.5% of the target amount. This is within the range of 0% to 200% vesting percentage of the target amount under the terms of the applicable RSU Award Agreements. Since the vesting of 129,611 RSUs is the final tranche of RSUs vesting under the applicable RSU Award Agreements, there was no unrecognized compensation associated with the RSUs as of December 31, 2013
	The table below summarizes the equity-based compensation costs recognized for each of the three years in the period ended December 31, 2013, and for the period November 10, 2005 (inception) through December 31, 2013:
										For the Period
										November 10, 2005
										(Inception)
	For Year Ended December 31,							through
	2013			2012		2011		December 31, 2013
	($ in thousands)
Restricted stock:
Employees	$	15,470		$	13,378	$	12,860		$	62,064
Non-employee directors		1,260			970		804			3,541
Stock options:
Employees		7,405			3,790		1,841			13,137
Restricted stock units (performance-based)		4,619			4,272		—			8,891
Deferred stock compensation(1)		—			—		—			1,828
	$	28,754		$	22,410	$	15,505		$	89,461
-1
In December 2008, the Company adopted a deferred compensation plan and provided certain executive officers the opportunity to defer under the Plan all or a portion of their salary and/or annual bonus for 2009. Amounts deferred under the Plan generally are deemed to be invested in a money market account prior to the IPO and shares of the Company's common stock following the IPO. Subject to accelerated payment under specified circumstances, the deferred amounts were distributed to these executives in January 2012 in the form of shares of the Company's common stock. All of the shares under the Plan were distributed to these executives during 2012.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2013
Employee Benefit Plan	'
Employee Benefit Plan	'
	16. Employee Benefit Plan
	In 2006, the Company established the Cobalt International Energy, L.P., defined contribution 401(k) plan (the Plan). All employees of the Company after three months of continuous employment are eligible to participate in the Plan. The plan is discretionary and provides a 6% employee contribution match as determined by the Company's Board of Directors. Effective December 31, 2009, the Plan was amended to discontinue the employer's matching contributions. Effective January 1, 2012, the Company reinstituted the 6% employee contribution match. For each of the years ended December 31, 2013, 2012 and 2011, the Company recorded $0.8 million, $0.5 million and $0 million, respectively, in benefits contributions to the Plan, which are included in the general and administrative expenses. For the period November 10, 2005 (inception) through December 31, 2013, the Company recorded a cumulative of $2.8 million in benefits contributions to the Plan.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
Income Taxes	'
	17. Income Taxes
	For the years ended December 31, 2013, 2012 and 2011, the Company recorded a net deferred tax asset of $461.6 million, $269.6 million and $177.2 million, respectively with a corresponding full valuation allowance of $461.6 million, $269.6 million and $177.2 million, respectively, for the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes.
	The components of the income tax provision (benefit) are as follows:
		Year Ended
		December 31,
		2013			2012			2011
		($ in thousands)
	Current taxes:
	U.S. federal	$	—		$	—		$	—
	Foreign		—			—			—
	Deferred taxes:
	U.S. federal		—			—			—
	Foreign		—			—			—
	Total	$	—		$	—		$	—
	The reconciliation of income taxes computed at the U.S. federal statutory tax rate to the Company's income tax expense (benefit) for each of the three years in the period ended December 31, 2013 are as follows:
		Year Ended December 31,
		2013			2012			2011
		($ in thousands)
	U.S.:
	Net income (loss) as reported	$	(387,210	)	$	(229,372	)	$	(76,231	)
	Less: net income (loss) applicable to period before corporate reorganization		—			—			—
	Foreign:
	Net income (loss) as reported		(201,814	)	$	(53,627	)	$	(57,406	)
	Less: net income (loss) applicable to period before corporate reorganization		—			—			—
	Net income (loss) applicable to period after corporate reorganization	$	(589,024	)	$	(282,999	)	$	(133,637	)
		Year Ended December 31,
		2013						2012					2011
		($ in thousands)
	Income tax expense (benefit) at the federal statutory rate	$	(206,159	)		35	%	$	(99,050	)	35	%	$	(46,773	)	35	%
	State income taxes, net of federal income tax benefit		(489	)		0.1	%		(512	)	0.2	%		(2,579	)	1.9	%
	Foreign income tax		(70,994	)		12.1	%		4,447		-1.6	%		(30,407	)	22.8	%
	Other		366			-0.1	%		2,678		-0.9	%		117		0.1	%
	Valuation allowance(1)		277,276			-47.1	%		92,437		-32.7	%		79,642		59.6	%
		$	—		$	—		$	—		—		$	—		—
	-1
	The change in the deferred tax asset valuation allowance of $277.3 million for the year ended December 31, 2013, excludes a $85.3 million net decrease in valuation allowance due to previously unrecorded foreign deferred tax assets and a deferred tax liability related to the Company's convertible debt instrument that did not impact the rate reconciliation.
	Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The significant components of the Company's deferred tax assets and liabilities were as follows:
		As of December 31,
		2013			2012
		($ in thousands)
	Short-term deferred tax liabilities:
	2.625% convertible senior notes due 2019(1)	$	17,061		$	—
	Total short-term deferred tax liabilities		17,061			—
	Long-term deferred tax liabilities:
	2.625% convertible senior notes due 2019	$	103,951		$	—
	Oil and gas properties		22,135			23,867
	Total long-term deferred tax liabilities		126,086			23,867
	Long-term deferred tax assets:
	Seismic and exploration costs		280,095			100,414
	Stock based compensation		20,842			12,340
	Domestic NOL carry forwards		273,163			158,310
	Foreign NOL carry forwards		28,633			20,624
	Other		1,976			1,818
	Valuation allowance		(461,562	)		(269,639	)
	Total long-term deferred assets		143,147			23,867
	Net long-term deferred assets		17,061			—
	Net deferred tax assets	$	—		$	—
	-1
	The recognition of the liability and equity components of the debt resulted in a taxable temporary basis difference and recorded as an adjustment to additional paid-in capital.
	The Company has established a full valuation allowance against the deferred tax assets where the Company has determined that it is more likely than not that all of the deferred tax assets will not be realized. Because of the full valuation allowance, no income tax expense or benefit is reflected on the consolidated statement of operations for each of the three years in the period ended December 31, 2013, 2012 and 2011.
	The NOL carryforward for federal and state income tax purposes of approximately $787.2 million and $51.9 million as of December 31, 2013 begins to expire in 2025 and 2024, respectively. The utilization of the NOL carryforwards is dependent upon generating sufficient future taxable income in the appropriate jurisdictions within the carryforward period.
	As of December 31, 2013, the Company had NOL carryforward for foreign income tax purposes of approximately $54.4 million which begins to expire in 2014. The Company has determined that it is more likely than not, that the foreign NOLs will not be fully realized. Therefore, a full valuation allowance was established for these net deferred tax assets.
	There were no unrecognized tax benefits or accrued interest or penalties associated with unrecognized tax benefits as of December 31, 2013 and 2012.

Commitments

Commitments	12 Months Ended
	Dec. 31, 2013
Commitments	'
Commitments	'
	18. Commitments
	The following table summarizes by period the payments due for the Company's estimated commitments, excluding long-term debt, as of December 31, 2013:
		Payments Due By Year
		2014		2015		2016		2017		2018		Thereafter
		($ in thousands)
	Drilling Rig and Related Contracts	$	349,000	$	521,000	$	295,000	$	207,000	$	—	$	—
	Operating Leases		13,000		11,000		8,000		5,000		4,000		8,000
	Lease Rentals(1)		6,000		6,000		4,000		3,000		1,000		1,000
	Social Payment Obligations(2)		49,019		50,619		62,854		5,714		5,714		—
	Total	$	417,019	$	588,619	$	369,854	$	220,714	$	10,714	$	9,000
	-1
	Relates to the annual delay rental payments payable to the Office of Natural Resources Revenue within the U.S. Department of the Interior with respect to the Company's U.S. Gulf of Mexico leases. These annual payments are required to maintain the leases from year to year.
	-2
	Includes the Company's contractual payment obligations for social projects such as the Sonangol Research and Technology Center and academic scholarships for Angolan students that the Company was and is contractually obligated to pay in consideration for the Angolan government granting it the licenses to explore for and develop hydrocarbons offshore Angola. Pursuant to the terms of the Risk Services Agreements for Blocks 9 and 21 and the Production Sharing Agreement for Block 20, the Company is not required to pay annual rental payments to maintain the licenses from year to year.
	The Company recorded $6.7 million, $12.1 million and $7.7 million of office and delay rental expense for the years ended December 31, 2013, 2012 and 2011, respectively, and a cumulative of $49.1 million for the period November 10, 2005 (Inception) through December 31, 2013.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2013
Segment Information	'
Segment Information	'
	19. Segment Information
	The Company currently has two geographic operating segments for its operations. The operating segments are focused in the deepwater U.S. Gulf of Mexico and offshore West Africa. The following tables provide the geographic operating segment information for each of the three years in the period ended December 31, 2013:
		United States			West Africa			Total
		($ in thousands)
	Year ended December 31, 2013
	Operating costs and expense	$	329,832		$	202,852		$	532,684
	Operating income (loss)		(329,832	)		(202,852	)		(532,684	)
	Other income (expense)								(56,340	)
	Net income (loss)							$	(589,024	)
	Additions to Property and Equipment, net(1)	$	44,124		$	332,395		$	376,519
	Year ended December 31, 2012
	Operating costs and expense	$	231,196		$	53,632		$	284,828
	Operating income (loss)		(231,196	)		(53,632	)		(284,828	)
	Other income (expense)								1,829
	Net income (loss)							$	(282,999	)
	Additions to Property and Equipment, net(1)	$	67,068		$	169,362		$	236,430
	Year ended December 31, 2011
	Operating costs and expense	$	80,425		$	57,411		$	137,836
	Operating income (loss)		(80,425	)		(57,411	)		(137,836	)
	Other income (expense)								4,199
	Net income (loss)							$	(133,637	)
	Additions to Property and Equipment, net(1)	$	(12,324	)	$	411,882		$	399,558
	-1
	These amounts are net of accumulated allowance for impairment on oil and gas properties and accumulated depreciation and amortization on other property and equipment.

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2013
Contingencies	'
Contingencies	'
	20. Contingencies
	The Company is not currently party to any legal proceedings. However, from time to time the Company may be subject to various lawsuits, claims and proceedings that arise in the normal course of business, including employment, commercial, environmental, safety and health matters. It is not presently possible to determine whether any such matters will have a material adverse effect on the Company's consolidated financial position, results of operations, or liquidity.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2013
Related Party Transactions	'
Related Party Transactions	'
	21. Related Party Transactions
	On February 20, 2013, the Company entered into software licensing and consulting service agreements with Quorum Business Solutions, Inc. ("Quorum") and Quorum Business Solutions (U.S.A.), Inc, related to certain enterprise resource planning software. Under these agreements, Quorum will license, host, and support this software for us for an initial term of three years. The approximate value of these agreements is $1.5 million. Quorum is owned in part by Riverstone Holdings, LLC, one of our former financial sponsors. For the year ended December 31, 2013, the Company incurred a total of $1.3 million in costs relating to Quorum. The Company did not have any material related party transactions for the years ended December 31, 2012 and 2011.

Selected_Quarterly_Financial_D

Selected Quarterly Financial Data-Unaudited	12 Months Ended
	Dec. 31, 2013
Selected Quarterly Financial Data-Unaudited	'
Selected Quarterly Financial Data-Unaudited	'
	22. Selected Quarterly Financial Data—Unaudited
	Unaudited quarterly financial data for the years ended December 31, 2013 and 2012 are as follows:
		1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
		($ in thousands)
	Year ended December 31, 2013
	Operating costs and expenses	$	112,452		$	65,365		$	145,663		$	209,204
	Operating income (loss)		(112,452	)		(65,365	)		(145,663	)		(209,204	)
	Net income (loss)		(128,087	)		(78,818	)		(160,000	)		(222,119	)
	Basic and diluted income (loss) per common share(1)	$	(0.31	)	$	(0.19	)	$	(0.39	)	$	(0.55	)
	Year ended December 31, 2012
	Operating costs and expenses	$	37,715		$	142,155		$	40,553		$	64,405
	Operating income (loss)		(37,715	)		(142,155	)		(40,553	)		(64,405	)
	Net income (loss)		(36,531	)		(140,723	)		(39,214	)		(66,531	)
	Basic and diluted income (loss) per common share(1)	$	(0.09	)	$	(0.35	)	$	(0.10	)	$	(0.16	)
	-1
	Totals may not add due to rounding.

Supplemental_Information_on_Oi

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited)	12 Months Ended
	Dec. 31, 2013
Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited)	'
Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited)	'
	23. Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited)
	The unaudited supplemental information on oil and gas exploration activities that follows is presented in accordance with supplemental disclosure requirements under ASC No. 932, "Extractive Activities—Oil and Gas" ("ASC No. 932") and the Securities and Exchange Commission's final rule, Modernization of Oil and Gas Reporting. Disclosures include (1) capitalized costs, costs incurred and results of operations related to oil and gas producing activities, (2)  net proved oil and gas reserves, and (3) a standardized measure of discounted future net cash flows relating to proved oil and gas reserves. Since the Company did not have any production activities for each of the three years in the period ended December 31, 2013, 2012 and 2011, there will be no disclosures on results of operations related to oil and gas producing activities.
	Capitalized Costs Related to Oil and Gas Activities
		U.S. Gulf			West Africa		Total
		of Mexico
		($ in thousands)
	As of December 31, 2013
	Unproved properties(1)	$	605,658		$	927,059	$	1,532,717
	Accumulated valuation allowance		(160,913	)		—		(160,913	)
			444,745			927,059		1,371,804
	Proved properties		92,579			—		92,579
	Net capitalized costs	$	537,324		$	927,059	$	1,464,383
	As of December 31, 2012
	Unproved properties	$	572,257		$	600,620	$	1,172,877
	Accumulated valuation allowance		(78,413	)		—		(78,413	)
			493,844			600,620		1,094,464
	Proved properties		—			—		—
	Net capitalized costs	$	493,844		$	600,620	$	1,094,464
	-1
	Unproved properties include capitalized costs net of sale/like-kind exchange of leasehold interest transactions that occurred in 2013 and 2012 of approximately $10.7 million and $0.8 million, respectively, for the U.S. Gulf of Mexico. No gain or loss was recognized for these transactions for the years ended December 31, 2013 and 2012.
	Costs Incurred in Oil and Gas Activities
	The following table reflects total costs incurred, both capitalized and expensed, for oil and gas property acquisition, exploration and development activities.
		U.S. Gulf			West Africa		Total
		of Mexico
		($ in thousands)
	Year ended December 31, 2013
	Property acquisition
	Unproved	$	37,584		$	—	$	37,584
	Proved		—			—		—
	Exploration
	Capitalized		158,806			469,879		628,685
	Expensed		48,688			25,525		74,213
	Development		54,133			—		54,133
	Total Costs Incurred	$	299,211		$	495,404	$	794,615
	Year ended December 31, 2012
	Property acquisition
	Unproved	$	19,961		$	—	$	19,961
	Proved		—			—		—
	Exploration
	Capitalized		178,295			168,309		346,604
	Expensed		32,874			28,709		61,583
	Development		—			—		—
	Total Costs Incurred	$	231,130		$	197,018	$	428,148
	Year ended December 31, 2011
	Property acquisition
	Unproved	$	—		$	337,126	$	337,126
	Proved		—			—		—
	Exploration
	Capitalized		11,214			96,849		108,063
	Expensed		10,707			21,532		32,239
	Development		—			—		—
	Total Costs Incurred	$	21,921		$	455,507	$	477,428
	All of the Company's proved reserves are located in the U.S. Gulf of Mexico. Reserve quantity information for the year ended December 31, 2013 is as follows:
		Natural Gas			Oil and		Equivalent
		(in Bcf)			Condensate		Volumes
					(in MMBbls)		(in MMBOE)
	Proved undeveloped reserves:
	Beginning of year		—
	Discoveries		3.4			7.9		8.5
	End of year		3.4			7.9		8.5
	The reserves as of December 31, 2013 presented above were prepared by the independent engineering firm, Netherland, Sewell & Associates, Inc. ("NSAI"). These reserves are located in the U.S. Gulf of Mexico. Proved oil and natural gas reserves are the estimated quantities of oil and natural gas which geological and engineering data demonstrate, with reasonable certainty, to be recoverable in future years from known reservoirs under economic and operating conditions (i.e., prices and costs) existing at the time the estimate is made. Proved developed oil and natural gas reserves are proved reserves that can be expected to be recovered through existing wells and equipment in place and under operating methods being utilized at the time the estimates were made. A variety of methodologies are used to determine the Company's proved reserve estimates. The principal methodologies employed are decline curve analysis, advance production type curve matching, petro-physics/log analysis and analogy. Some combination of these methods is used to determine reserve estimates in substantially all of the Company's fields. The Company emphasizes that reserve estimates are inherently imprecise and that estimates of new discoveries and undeveloped locations are more imprecise than estimates of established proved producing oil and gas properties. Accordingly, these estimates are expected to change as future information becomes available.
	Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves
	The Company follows the guidelines prescribed in ASC No. 932 for computing a standardized measure of future net cash flows and changes therein relating to estimated proved reserves. The following summarizes the policies used in the preparation of the accompanying oil and natural gas reserve disclosures, standardized measures of discounted future net cash flows from proved oil and natural gas reserves and the reconciliations of standardized measures from year to year.
The information is based on estimates of proved reserves attributable to the Company's interest in oil and natural gas properties as of December 31, 2013. The Company did not have proved reserves as of December 31, 2012. These estimates were prepared by NSAI.
The standardized measure of discounted future net cash flows from production of proved reserves was developed as follows:
-1
Estimates are made of quantities of proved reserves and future periods during which they are expected to be produced based on year-end economic conditions.
-2
The estimated future cash flows are compiled by applying the twelve month average of the first of the month prices of crude oil and natural gas relating to the Company's proved reserves to the year-end quantities of those reserves for reserves.
-3
The future cash flows are reduced by estimated production costs, costs to develop and produce the proved reserves and abandonment costs, all based on year-end economic conditions, plus Company overhead incurred.
-4
Future income tax expenses are based on year-end statutory tax rates giving effect to the remaining tax basis in the oil and natural gas properties, other deductions, credits and allowances relating to the Company's proved oil and natural gas reserves.
-5
Future net cash flows are discounted to present value by applying a discount rate of 10%.
The assumptions used to compute the standardized measure are those prescribed by the U.S. Generally Accepted Accounting Principles. These assumptions do not necessarily reflect the Company's expectations of actual revenues to be derived from those reserves, nor their present value. The limitations inherent in the reserve quantity estimation process, as discussed previously, are equally applicable to the standardized measure computations, since these reserve quantity estimates are the basis for the valuation process. The Company emphasizes that reserve estimates are inherently imprecise and that estimates of new discoveries and undeveloped locations are more imprecise than estimates of established proved producing oil and gas properties. The standardized measure of discounted future net cash flows does not purport, nor should it be interpreted, to present the fair value of the Company's oil and natural gas reserves. An estimate of fair value would also take into account, among other things, the recovery of reserves not presently classified as proved, anticipated future changes in prices and costs and a discount factor more representative of the time value of money and the risks inherent in reserve estimates.
Prices used in the report prepared by NSAI are based on the 12-month unweighted arithmetic average of the first-day-of-the-month price for each month in the period January through December 2013. For oil volumes, the average Light Louisiana Sweet spot price of $107.13 per barrel is adjusted for quality, transportation fees, and a regional price differential. For gas volumes, the average Henry Hub spot price of $3.670 per MMbtu is adjusted for energy content, transportation fees, and a regional price differential. All prices are held constant throughout the lives of the properties. For the proved reserves, the average adjusted product prices weighted by production over the remaining lives of the properties are $103.90 per barrel of oil and $3.507 per Mcf of gas.
Information with respect to the Company's estimated discounted future net cash flows related to its proved natural gas reserves as of December 31, 2013 is as follows ($ in thousands):
	2013
Future cash inflows	$	830,287
Future production costs		(6,400	)
Future development costs		(302,278	)
Future income tax expense(1)		—
Future net cash flows		521,609
10% annual discount for estimated timing of cash flows		(244,976	)
Standardized measure of discounted future net cash flows	$	276,633
-1
There is no future income tax expense as of December 31, 2013, as the tax basis of the oil and gas properties in the United States and net operating losses attributable to oil and gas operations exceed the future net revenues.
Information with respect to the Company's standardized measure of discounted future net cash flows as of December 31, 2013 is as follows ($ in thousands):
	2013
Standardized measure, beginning	$	—
Discoveries		276,633
Standardized measure, ending	$	276,633

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying consolidated financial statements include the financial statements of Cobalt International Energy, Inc. and all of its wholly owned subsidiaries. All significant intercompany transactions and amounts have been eliminated for all years presented. Because the Company is a development stage enterprise, it has presented its financial statements in accordance with accounting guidance relating to "Development Stage Entities."
	At December 31, 2013, the accompanying consolidated financial statements include the accounts of Cobalt and its wholly owned subsidiary, Cobalt International Energy, L.P. ("Partnership"). Prior to the effective date of a corporate reorganization, both entities were under common control arising from common direct or indirect ownership of each. The transfer of the Partnership interests to Cobalt represented a reorganization of entities under common control and was accounted for at historical cost.
Reclassifications	'
	Reclassifications
	Certain reclassifications have been made to prior periods' financial statements to conform to the current presentation in the consolidated statements of cash flows.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with United States generally accepted accounting principles ("GAAP") requires the Company to make estimates and assumptions that affect the reported amounts of assets including proved reserves and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates the Company makes include (a) accruals related to expenses, (b) assumptions used in estimating fair value of equity based awards and the fair value of the liability component of the convertible senior notes and (c) assumptions used in impairment testing. Although the Company believes these estimates are reasonable, actual results could differ from these estimates.
Fair Value Measurements	'
	Fair Value Measurements
	The fair values of the Company's cash and cash equivalents, joint interest and other receivables, restricted funds and investments approximate their carrying amounts due to their short-term duration. The hierarchy below lists three levels of fair value based on the extent to which inputs used in measuring fair value are observable in the market. The Company categorizes each of its fair value measurements as applicable to one of these three levels based on the lowest level input that is significant to the fair value measurement in its entirety. The levels are:
	Level 1—Quoted prices in active markets that are accessible at the measurement date for identical assets or liabilities. This category includes the Company's cash and money market funds.
	Level 2—Quoted prices in non-active markets or in active markets for similar assets or liabilities, and inputs other than quoted prices that are observable, for the asset or liability, either directly or indirectly for substantially the full contractual term of the asset or liability being measured. This category includes the Company's U.S. Treasury bills, U.S. Treasury notes, U.S. Government agency securities, commercial paper, corporate bonds, municipal bonds and certificates of deposits.
	Level 3—Inputs that are generally unobservable and typically reflect management's estimate of assumptions that market participants would use in pricing the asset or liability. The Company does not currently have any financial instruments categorized as Level 3.
Revenue Recognition	'
	Revenue Recognition
	The Company will follow the "sales" (or cash) method of accounting for oil and gas revenues. Under this method, the Company will recognize revenues on the volumes sold. The volumes sold may be more or less than the volumes to which the Company is entitled based on its ownership interest in the property. These differences result in a condition known in the industry as a production imbalance. For the years ended December 31, 2013, 2012, 2011 and for the period November 10, 2005 (Inception) through December 31, 2013, no revenues have been recognized in these consolidated financial statements.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	Cash and cash equivalents consist of demand deposits and funds invested in highly liquid instruments with maturities of three months or less from the date of purchase. Demand deposits typically exceed federally insured limits; however, the Company periodically assesses the financial condition of the institutions where these funds are held as well as the credit ratings of the issuers of the highly liquid instruments and believes that the credit risk is minimal.
Restricted Funds	'
	Restricted Funds
	Restricted funds primarily consist of funds held in escrow accounts and collateral for letters of credit relating to our operations in the U.S. Gulf of Mexico and offshore Angola.
Investments	'
	Investments
	The Company's policy on accounting for its investments, which consist entirely of debt securities money market funds and certificates of deposit, is based on the accounting guidance relating to "Accounting for Certain Investments in Debt and Equity Securities." The Company considers all highly liquid interest-earning investments with a maturity of three months or less at the date of purchase to be cash equivalents. Investments with original maturities of greater than three months and remaining maturities of less than one year are classified as short-term investments. Investments with maturities beyond one year are classified as long-term investments. The debt securities are carried at amortized costs and classified as held-to-maturity securities as the Company has the positive intent and ability to hold them until they mature. The net carrying value of held-to-maturity debt securities is adjusted for amortization of premiums and accretion of discounts to maturity over the life of the securities. Held-to-maturity debt securities are stated at amortized cost, which approximated fair market value as of December 31, 2013 and 2012. Money market funds and certificates of deposit are carried at face value. Income related to these securities is reported as a component of interest income in the Company's consolidated statement of operations. See Note 7—Investments.
	Investments are considered to be impaired when a decline in fair value is determined to be other-than-temporary. The Company conducts a regular assessment of its debt securities with unrealized losses to determine whether securities have other-than-temporary impairment ("OTTI"). This assessment considers, among other factors, the nature of the securities, credit rating or financial condition of the issuer, the extent and duration of the unrealized loss, market conditions and whether the Company intends to sell or whether it is more likely than not that the Company will be required to sell the debt securities. As of December 31, 2013 and 2012, the Company has no OTTI in its debt securities.
Capitalized Interest	'
	Capitalized Interest
	For exploration and development projects that have not commenced production, interest is capitalized as part of the historical cost of developing and constructing assets. Capitalized interest is determined by multiplying the Company's weighted-average borrowing cost on debt by the average amount of qualifying costs incurred. Once an asset subject to interest capitalization is completed and placed in service, the associated capitalized interest is expensed through depreciation or impairment. See Note 9—Property, Plant, and Equipment and Note 11—Long-term Debt.
Joint Interest and Other Receivables	'
	Joint Interest and Other Receivables
	Joint interest and other receivables result primarily from billing shared costs under the respective operating agreements to the Company's partners. These receivables are usually settled within 30 days of the invoice date.
Property, Plant, and Equipment	'
	Property, Plant, and Equipment
	The Company uses the "successful efforts" method of accounting for its oil and gas properties. Acquisition costs for unproved leasehold properties and costs of drilling exploration wells are capitalized pending determination of whether proved reserves can be attributed to the areas as a result of drilling those wells. Under the successful efforts method of accounting, proved leasehold costs are capitalized and amortized over the proved developed and undeveloped reserves on a units-of-production basis. Successful drilling costs, costs of development and developmental dry holes are capitalized and amortized over the proved developed reserves on a units-of-production basis. Significant unproved leasehold costs are capitalized and are not amortized, pending an evaluation of their exploration potential. Unproved leasehold costs are assessed periodically to determine if an impairment of the cost of individual properties has occurred. Factors taken into account for impairment analysis include results of the technical studies conducted, lease terms and management's future exploration plans. The cost of impairment is charged to expense in the period in which it occurs. Costs incurred for exploration dry holes, geological and geophysical work (including the cost of seismic data), and delay rentals are charged to expense as incurred. Costs of other property and equipment are depreciated on a straight-line basis based on their respective useful lives.
Asset Retirement Obligations	'
	Asset Retirement Obligations
	The Company currently does not have any oil and natural gas production or any legal obligations to incur decommissioning costs. Should such production occur in the future, the Company expects to have significant obligations under its lease agreements and federal regulation to remove its equipment and restore land or seabed at the end of oil and natural gas production operations. These asset retirement obligations are primarily associated with plugging and abandoning wells and removing and disposing of offshore oil and natural gas platforms. Estimating the future restoration and removal cost is difficult and requires the Company to make estimates and judgments because most of the removal obligations are many years in the future and contracts and regulation often have vague descriptions of what constitutes removal. Asset removal technologies and cost are constantly changing, as are regulatory, political, environmental, safety and public relations considerations. Pursuant to the accounting guidance relating to "Assets Retirement Obligations", the Company is required to record a separate liability for the estimated fair value of its asset retirement obligations, with an offsetting increase to the related oil and natural gas properties representing asset retirement costs on its balance sheet. The cost of the related oil and natural gas asset, including the asset retirement cost, is depreciated over the useful life of the asset. The estimated fair value of asset retirement obligations is measured by reference to the expected future cash outflows required to satisfy the retirement obligation discounted at the Company's credit-adjusted risk-free interest rate. Accretion expense is recognized over time as the discounted liability is accreted to its expected settlement value.
	Inherent to the present value calculation are numerous estimates, assumptions and judgments, including the ultimate settlement amounts, inflation factors, credit adjusted risk-free rates, timing of settlement and changes in the legal, regulatory, environmental and political environments. To the extent future revisions to these assumptions impact the present value of the abandonment liability, the Company will make corresponding adjustments to both the asset retirement obligation and the related oil and natural gas property asset balance. Increases in the discounted abandonment liability and related oil and natural gas assets resulting from the passage of time will be reflected as additional accretion and depreciation expense in the consolidated statements of operations.
Inventory	'
	Inventory
	Inventories consist of various tubular products that are used in the Company's drilling programs. The products are stated at the average cost. Cost is determined using a weighted average method comprised of the purchase price and other directly attributable costs.
Income Taxes	'
	Income Taxes
	The Company applied the liability method of accounting for income taxes in accordance with accounting guidance related to "Income Taxes" as clarified by "Accounting for Uncertainty in Income Taxes." Under this method, deferred tax assets and liabilities are determined by applying tax rates in effect at the end of a reporting period to the cumulative temporary differences between the tax bases of assets and liabilities and their reported amounts in the financial statements. Since the Company is in development stage and there can be no assurance that the Company will generate any earnings or any specific level of earnings in future years, the Company has established a valuation allowance that equals its net deferred tax assets. See Note 17.
Equity-Based Compensation	'
	Equity-Based Compensation
	The Company accounts for stock-based compensation at fair value. The Company grants various types of stock-based awards including stock options, restricted stock and performance-based awards. The fair value of stock option awards is determined using the Black-Scholes-Merton option-pricing model. For restricted stock awards with market conditions, the fair value of the awards is measured using the asset-or-nothing option pricing model. Restricted stock awards without market conditions and the performance-based awards are valued using the market price of the Company's common stock on the grant date. The Company records compensation cost, net of estimated forfeitures, on a straight-line basis for stock-based compensation awards over the requisite service period except for performance-based awards. For performance-based awards, compensation cost is recognized over the requisite service period as and when the Company determines that the achievement of the performance condition is probable, using the per-share fair value measured at grant date. See Note 15.
Earnings (Loss) Per Share	'
	Earnings (Loss) Per Share
	Basic income (loss) per share was calculated by dividing net income or loss applicable to common shares by the weighted average number of common shares outstanding during the periods presented. The calculation of diluted income (loss) per share should include the potential dilutive impact of non-vested restricted shares, non-vested restricted stock units, outstanding stock options and the Company's 2.625% convertible senior notes due 2019, during the period, unless their effect is anti-dilutive. For the year ended December 31, 2013, 6,735,046 shares of non-vested restricted stock, non-vested restricted stock units, outstanding stock options and 2.625% convertible senior notes due 2019, were excluded from the diluted income (loss) per share because they are anti-dilutive. For the year ended December 31, 2012, 5,617,697 shares of non-vested restricted stock, non-vested restricted stock units and outstanding stock options were excluded from the diluted income (loss) per share because they are anti-dilutive.
Operating Costs and Expenses	'
	Operating Costs and Expenses
	Expenses consist primarily of the costs of acquiring and processing of geological and geophysical data, exploration and appraisal drilling expenses, consultants, telecommunications, payroll and benefit costs, information system and legal costs, office rent, contract costs, and bookkeeping and audit fees.

Cash_and_Cash_Equivalents_Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2013
Cash and Cash Equivalents	'
Cash and cash equivalents	'
		December 31,
		2013		2012
		(in thousands)
	Cash at banks	$	82,428	$	65,935
	Money market funds		75,039		1,105,148
	Held-to-maturity securities(1)		34,993		254,732
		$	192,460	$	1,425,815
	-1
	These securities mature three months or less from date of purchase.

Restricted_Funds_Tables

Restricted Funds (Tables)	12 Months Ended
	Dec. 31, 2013
Restricted Funds	'
Schedule of restricted funds	'
		December 31,
		2013		2012
		(in thousands)
	Short-term:
	Collateral on Letters of Credit for Angola(1)	$	200,339	$	—
	Ensco 8503 escrow account(2)		—		90,440
		$	200,339	$	90,440
	Long-term:
	Ensco 8503 escrow account(2)		—		90,440
	Collateral on Letters of Credit for Angola(1)		104,496		304,492
	Other vendor restricted deposits		—		720
		$	104,496	$	395,652
	-1
	As of December 31, 2013 and December 31, 2012, $304.8 million and $304.5 million, respectively, was held in a collateral account established to secure letters of credit issued in support of the Company's contractually agreed work program obligations on Blocks 9, 20 and 21 offshore Angola. As of December 31, 2013, the collateral in this account was invested in U.S. Treasury bills and Treasury notes purchased at discounts and at premiums, respectively, resulting in a net carrying value of $304.8 million. The contractual maturities of these securities are within one year. The $200.3 million classified as short-term restricted funds at December 31, 2013 includes $153.6 million of cash collateral associated with work program obligations which have been completed for Blocks 20 and 21 and for which the Company expects to receive distribution of the collateral in 2014. The remaining $46.7 million secures work program obligations of $45.3 million for Block 9 for which the initial exploration phase expires on March 1, 2014, if not extended.
	-2
	As of December 31, 2012, $180.9 million was held in an escrow account established in December 2009 as a guarantee of performance to Ensco Offshore Company ("Ensco") for the Ensco 8503 drilling rig contract. As of December 31, 2013 the escrow account balance was refunded to the Company pursuant to the terms of the drilling rig contract. The drilling rig contract expired in January 2014.

Joint_Interests_and_Other_Rece1

Joint Interests and Other Receivables (Tables)	12 Months Ended
	Dec. 31, 2013
Joint Interests and Other Receivables	'
Schedule of joint interest and other receivables	'
		December 31,
		2013		2012
		(in thousands)
	Partners in the U.S. Gulf of Mexico	$	68,664	$	52,439
	Partners in West Africa(1)		46,897		2,185
	Accrued interest on investment securities		5,632		3,647
	Other		3,446		3,321
		$	124,639	$	61,592
	-1
	The amount of $46.9 million as of December 31, 2013 includes $15.7 million related to the Company's partners on Block 20 offshore Angola and $31.2 million related to the outstanding balance due from the Company's partners on Blocks 9 and 21 offshore Angola, a portion of which is currently past due but the Company expects to recover.

Prepaid_Expenses_and_Other_Cur1

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2013
Prepaid Expenses and Other Current Assets	'
Schedule of prepaid expenses and other current assets	'
		December 31,
		2013		2012
		(in thousands)
	Prepaid expenses:
	Prepaid expenses(1)	$	37,796	$	11,729
	Other current assets:
	Cash advance to joint venture partner(2)		9,685		351
	Rig mobilization, regulatory and other related costs(3)		8,376		11,861
		$	55,857	$	23,941
	-1
	As of December 31, 2013, prepaid expenses include $11.5 million of the prepaid and unamortized portion of payments made for software licenses, related maintenance fees, insurance and $26.3 million of prepaid costs associated with the Ensco drilling rig contract. The drilling rig contract terminated in January 2014 and upon receipt and application of prepaid amounts against the final invoice from Ensco, any remaining balance of the prepayment will be refunded to the Company. As of December 31, 2012, the $11.7 million in prepaid expenses consisted of the prepaid and unamortized portion of payments made for software licenses, related maintenance fees and insurance.
	-2
	As of December 31, 2013, the $9.7 million in other current assets relates to payment of cash calls made to our joint interest partner, Total Gabon, for operating costs to drill the Diaman #1B exploration well. This prepayment will be applied against the joint interest bills upon receipt from Total Gabon.
	-3
	As of December 31, 2013, the $8.4 million in other current assets relates to the short-term portion of the mobilization and regulatory acceptance testing costs associated with the SSV Catarina drilling rig. As of December 31, 2012, the $11.9 million in other current assets relates to the remaining balance of the mobilization and equipment upgrade costs associated with the Ensco 8503 drilling rig. These costs are amortized on a straight-line basis over the terms of the respective drilling contracts.

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2013
Investments	'
Schedule of fair value of held-to-maturity securities recorded at amortized cost	'
		December 31,
		2013		2012
		(in thousands)
	U.S. Treasury securities	$	304,834	$	483,775
	Corporate securities		856,002		510,691
	Commercial paper		408,033		562,975
	Certificates of deposit		105,000		7,000
	Total	$	1,673,869	$	1,564,441
Schedule of held-to-maturity securities included in the company's balance sheets	'
		December 31,
		2013		2012
		(in thousands)
	Cash and cash equivalents	$	34,993	$	254,732
	Short-term investments		1,319,380		789,668
	Short-term restricted funds		200,339		90,440
	Long-term restricted funds		104,496		393,334
	Long-term investments		14,661		36,267
		$	1,673,869	$	1,564,441
Schedule of contractual maturities of held-to-maturity securities	'
		December 31,
		2013				2012
		Amortized		Estimated Fair		Amortized		Estimated Fair
		Cost		Value		Cost		Value
		($ in thousands)
	Within 1 year	$	1,659,208	$	1,659,208	$	1,528,174	$	1,528,174
	After 1 year		14,661		14,661		36,267		36,267
		$	1,673,869	$	1,673,869	$	1,564,441	$	1,564,441

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2013
Fair Value Measurements	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'
		Level 1				Level 2
		Carrying		Fair		Carrying		Fair		Balance as of
		Value		Value(1)		Value		Value(1)		December 31,
										2013
		($ in thousands)
	Cash and cash equivalents:
	Cash	$	82,428	$	82,428	$	—	$	—	$	82,428
	Money market funds		75,039		75,039		—		—		75,039
	Commercial paper		—		—		9,993		9,993		9,993
	Certificate of deposits						25,000		25,000		25,000
	Subtotal		157,467		157,467		34,993		34,993		192,460
	Short-term restricted funds:
	U.S. Treasury notes		—		—		200,339		200,339		200,339
	Subtotal		—		—		200,339		200,339		200,339
	Short-term investments:
	Corporate bonds		—		—		848,307		848,307		848,307
	Commercial paper		—		—		391,073		391,073		391,073
	Certificates of deposits		—		—		80,000		80,000		80,000
	Subtotal		—		—		1,319,380		1,319,380		1,319,380
	Long-term restricted funds:
	U.S. Treasury notes		—		—		104,496		104,496		104,496
	Subtotal		—		—		104,496		104,496		104,496
	Long-term investments:
	Commercial paper		—		—		6,967		6,967		6,967
	Corporate bonds		—		—		7,694		7,694		7,694
	Subtotal		—		—		14,661		14,661		14,661
	Total	$	157,467	$	157,467	$	1,673,869	$	1,673,869	$	1,831,336
		Level 1				Level 2
										Balance as of
										December 31,
		Carrying Value		Fair Value(1)		Carrying Value		Fair Value(1)		2012
		($ in Thousands)
	Cash and cash equivalents:
	Cash	$	65,935	$	65,935	$	—	$	—	$	65,935
	Money market funds		1,105,148		1,105,148		—		—		1,105,148
	Commercial paper		—		—		247,206		247,206		247,206
	Corporate bonds		—		—		7,526		7,526		7,526
	Subtotal		1,171,083		1,171,083		254,732		254,732		1,425,815
	Short-term restricted funds:
	U.S. Treasury bills		—		—		90,440		90,440		90,440
	Subtotal		—		—		90,440		90,440		90,440
	Short-term investments:
	Corporate bonds		—		—		466,898		466,898		466,898
	Commercial paper		—		—		315,769		315,769		315,769
	Certificate of deposits		—		—		7,001		7,001		7,001
	Subtotal		—		—		789,668		789,668		789,668
	Long-term restricted funds:
	Money market funds		2,318		2,318		—		—		2,318
	U.S. Treasury bills		—		—		178,216		178,216		178,216
	U.S. Treasury notes		—		—		215,118		215,118		215,118
	Subtotal		2,318		2,318		393,334		393,334		395,652
	Long-term investments:
	Corporate bonds		—		—		36,267		36,267		36,267
	Subtotal		—		—		36,267		36,267		36,267
	Total	$	1,173,401	$	1,173,401	$	1,564,441	$	1,564,441	$	2,737,842
	-1
	As of December 31, 2013 and 2012, the Company did not record any OTTI on these assets.

Property_Plant_and_Equipment_T

Property, Plant, and Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
Property, Plant, and Equipment	'
Schedule of Property, Plant, and Equipment	'
				December 31,
		Estimated
		Useful Life
		(Years)		2013			2012
				($ in thousands)
	Oil and Gas Properties:
	Proved properties:
	Well and development costs			$	92,579		$	—
	Total proved properties				92,579			—
	Unproved properties:
	Oil and gas leasehold			$	754,894		$	721,853
	Less: accumulated valuation allowance				(160,913	)		(78,413	)
					593,981			643,440
	Exploration wells in process				777,823			451,024
	Total unproved properties				1,371,804			1,094,464
	Total oil and gas properties, net				1,464,383			1,094,464
	Other Property and Equipment:
	Computer equipment and software	3			5,115			3,166
	Office equipment and furniture	3 - 5			2,132			2,093
	Vehicles	3			265			268
	Leasehold improvements	3 - 10			2,456			2,298
	Running tools and equipment	3			6,318			—
					16,286			7,825
	Less: accumulated depreciation and amortization(1)				(4,394	)		(2,533	)
	Total other property and equipment, net				11,892			5,292
	Property, plant, and equipment, net			$	1,476,275		$	1,099,756
	-1
	During the year ended December 31, 2012, the Company wrote off $2.2 million of old computer equipment and leasehold improvements which were fully depreciated and therefore had no impact on the consolidated statements of operations and consolidated statements of cash flow.
Schedule of net changes in capitalized exploration well costs	'
		December 31,			December 31,			December 31,
		2013			2012			2011
		($ in thousands)
	Beginning of period	$	451,024		$	178,338		$	106,881
	Additions to capitalized exploration
	U.S. Gulf of Mexico:
	Exploration well costs		154,877			178,295			11,214
	Capitalized interest		3,928			—			—
	West Africa:
	Exploration well costs		457,608			168,309			96,849
	Capitalized interest		12,271			—			—
	Reclassifications to wells, facilities, and equipment based on determination of proved reserves		(38,446	)		—			—
	Amounts charged to expense(1)		(263,439	)		(73,918	)		(36,606	)
	End of period	$	777,823		$	451,024		$	178,338
	-1
	The amount of $263.4 million for the year ended December 31, 2013 represents $120.0 million of impairment charges on exploration wells drilled in the U.S. Gulf of Mexico which did not encounter commercial hydrocarbons, $126.3 million of impairment charges on exploration wells drilled offshore Angola which failed to flow measurable hydrocarbons from drill stem tests and a portion of the cost of exploration wells drilled offshore Angola that were determined to have no utility in the lowest interval beneath the pay zone and $17.1 million of impairment charges on the exploration well drilled offshore Gabon which needed to be re-spud due to mechanical problems with the wellbore. The amount of $73.9 million for the year ended December 31, 2012 represents impairment charges on exploration wells drilled in the U.S. Gulf of Mexico which did not encounter commercial hydrocarbons.
Schedule of cumulative costs of capitalized exploration well costs	'
		December 31,			December 31,
		2013			2012
		($ in thousands)
	Cumulative costs:
	U.S. Gulf of Mexico
	Exploration well costs	$	204,707		$	208,275
	Capitalized interest		3,928			—
	West Africa
	Exploration well costs		556,917			242,749
	Capitalized interest		12,271			—
		$	777,823		$	451,024
	Well costs capitalized for a period greater than one year after completion of drilling (included in table above)	$	399,775		$	194,853

Other_Assets_Table

Other Assets (Table)	12 Months Ended
	Dec. 31, 2013
Other Assets	'
Schedule of other assets	'
		December 31,
		2013		2012
		(in thousands)
	Debt issue cost(1)	$	20,983	$	23,042
	Long-term portion of prepaid shorebase leases		3,241		—
	Rig mobilization costs(2)		11,153		—
	Long-term accounts receivable(3)		17,923		—
	Other		437		—
		$	53,737	$	23,042
	-1
	As of December 31, 2013 and 2012, the $21.0 million and $23.0 million in debt issue cost relate to the issuance of the Company's 2.625% convertible senior notes due 2019, as described in Note 11, and which are amortized over the life of the notes using the effective interest method.
	-2
	The $11.2 million as of December 31, 2013 relates to costs associated with the long-term mobilization and the regulatory acceptance testing of the SSV Catarina drilling rig. These costs are amortized over the term of the drilling rig contract.
	-3
	On March 16, 2012, Angola enacted Presidential Decree No. 3/12, which, among other things, provided that Angolan private petroleum companies are exempt from any requirement to carry Sonangol P&P. As a result of this statute, one of the Company's partners in Angola has taken the position that it is no longer required to pay a 3.75% cost interest attributable to Sonangol P&P's share of expenses. As of December 31, 2013, these expenditures totaled approximately $17.9 million, which is classified as a long term receivable as the Company expects this amount to be recovered pursuant to the terms of the Risk Services Agreements governing Blocks 9 and 21.

Longterm_Debt_Tables

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Long-term Debt	'
Schedule of the carrying amounts of the liability components of the Notes	'
		December 31, 2013								December 31, 2012
		Principal			Unamortized			Carrying		Principal		Unamortized			Carrying
		Amount			discount(1)			Amount		Amount		discount			Amount
		($ in thousands)
	Carrying amount of liability component
	2.625% convertible senior notes due 2019	$	1,380,000		$	(344,020	)	$	1,035,980	$	1,380,000	$	(388,809	)	$	991,191
	-1
	Unamortized discount will be amortized over the remaining life of the Notes which is 6 years.
Schedule of carrying amounts of the equity components of the Notes	'
		December 31,			December 31,
		2013			2012
		($ in thousands)
	Debt discount relating to value of conversion option	$	390,540		$	390,540
	Debt issue costs		(9,124	)		(9,124	)
	Total	$	381,416		$	381,416
Schedule of interest expense	'
										For the Period
										November 10, 2005
										(Inception)
		For Year Ended December 31,								through
		2013			2012			2011		December 31, 2013
		($ in thousands)
	Interest expense associated with accrued interest(1)	$	18,529		$	1,294		$	—	$	19,823
	Interest expense associated with accretion of debt discount		44,789			1,843			—		46,632
	Interest expense associated with amortization of debt issue costs		2,058			75			—		2,133
	Total	$	65,376		$	3,212		$	—	$	68,588
	-1
	The $18.5 million and $1.3 million for the years ended December 31, 2013 and 2012, respectively, represent interest expense net of capitalized amounts of $17.7 million and $0 million, respectively.

Contractual_Obligations_Tables

Contractual Obligations (Tables)	12 Months Ended
	Dec. 31, 2013
Contractual Obligations	'
Summary of components of short-term and long-term contractual obligations	'
		December 31,
		2013		2012
		($ in thousands)
	Short-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	150	$	150
	Social obligation payments for Block 21, offshore Angola		300		300
	Social obligation and bonus payments for Block 20, offshore Angola(1)(2)		48,569		48,569
		$	49,019	$	49,019
	Long-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	669	$	848
	Social obligation payments for Block 21, offshore Angola		1,381		1,684
	Social obligation and bonus payments for Block 20, offshore Angola(2)		122,851		165,706
		$	124,901	$	168,238
	-1
	$42.9 million of this amount was paid in January 2014.
	-2
	The total amount of social obligation payments for Block 20 has been capitalized. See Note 9.

Seismic_and_Exploration_Expens1

Seismic and Exploration Expenses (Tables)	12 Months Ended
	Dec. 31, 2013
Seismic and Exploration Expenses	'
Schedule of seismic and exploration expenses	'
								For the Period
								November 10, 2005
								(Inception)
		For Year Ended December 31,						through
		2013		2012		2011		December 31, 2013
		($ in thousands)
	Seismic costs	$	63,721	$	42,447	$	20,443	$	405,769
	Seismic cost recovery(1)		—		—		—		(25,126	)
	Leasehold delay rentals		6,660		6,383		6,075		39,562
	Force Majeure expense(2)		—		—		—		13,549
	Drilling rig expense		3,832		12,753		5,721		30,631
		$	74,213	$	61,583	$	32,239	$	464,385
	-1
	These amounts represent reimbursement from partners of past seismic costs incurred by the Company.
	-2
	These amounts represent expenditures resulting from suspension of drilling activities in the U.S. Gulf of Mexico as a result of the explosion and sinking of the Deepwater Horizon drilling rig in the U.S. Gulf of Mexico, the resulting oil spill and the regulatory response thereto and other exploration expenses.

Equity_based_Compensation_Tabl

Equity based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
Equity based Compensation	'
Schedule of restricted stock awarded to employees and restricted stock units	'
		Years Ended December 31,
		2013					2012					2011
		Restricted			Weighted		Restricted			Weighted		Restricted			Weighted
		Shares			Average		Shares			Average		Shares			Average
					Grant Date					Grant Date					Grant Date
					Fair Value					Fair Value					Fair Value
					Per Share					Per Share					Per Share
	Non-vested shares at beginning of year		4,040,825		$	13.05		4,599,783		$	11.27		5,570,895		$	9.77
	Granted		620,840		$	24.58		487,710		$	26.01		214,792		$	8.54
	Vested		(239,317	)	$	17.37		(738,628	)	$	13.05		(1,185,904	)	$	3.75
	Forfeited or expired		(87,462	)	$	20.91		(308,040	)	$	12.17		—			—
	Non-vested shares at end of year		4,334,886		$	14.31		4,040,825		$	13.05		4,599,783		$	11.27
	Weighted-average vesting period remaining		1.22 years					1.87 years					2.5 years
	Unrecognized compensation ($ in thousands)	$	22,467				$	23,827				$	29,559
Schedule of assumptions used to determine the fair value of each stock option granted using the Black-Scholes-Merton option-pricing model	'
		2013
	Expected Term in Years		6.68
	Expected Volatility		61.58	%
	Expected Dividends		0	%
	Risk-Free Interest Rate		1.28	%
Schedule of stock option activities	'
		Shares			Weighted		Weighted-Average			Aggregate
					Average		Remaining			Intrinsic Value
					Exercise		Contractual Term			(thousands)
					Price		(years)
	Outstanding at January 1, 2013		1,434,393		$	17.87		8.3		$	12,158
	Granted		959,023		$	23.78		9.1
	Exercised		(13,985	)	$	12.45		6.9		$	219
	Forfeited or expired		(40,713	)	$	22.89
	Outstanding at December 31, 2013		2,338,718		$	20.24		8		$	3,937
	Vested or expected to vest at December 31, 2013		1,568,748		$	23.83		8.5		$	965
	Exercisable at December 31, 2013		737,973		$	12.45		6.9		$	2,952
Schedule of recognized equity-based compensation costs	'
										For the Period
										November 10, 2005
										(Inception)
		For Year Ended December 31,								through
		2013			2012		2011			December 31, 2013
		($ in thousands)
	Restricted stock:
	Employees	$	15,470		$	13,378	$	12,860		$	62,064
	Non-employee directors		1,260			970		804			3,541
	Stock options:
	Employees		7,405			3,790		1,841			13,137
	Restricted stock units (performance-based)		4,619			4,272		—			8,891
	Deferred stock compensation(1)		—			—		—			1,828
		$	28,754		$	22,410	$	15,505		$	89,461
	-1
	In December 2008, the Company adopted a deferred compensation plan and provided certain executive officers the opportunity to defer under the Plan all or a portion of their salary and/or annual bonus for 2009. Amounts deferred under the Plan generally are deemed to be invested in a money market account prior to the IPO and shares of the Company's common stock following the IPO. Subject to accelerated payment under specified circumstances, the deferred amounts were distributed to these executives in January 2012 in the form of shares of the Company's common stock. All of the shares under the Plan were distributed to these executives during 2012.
Restricted stock units (performance-based)	'
Equity based Compensation	'
Schedule of stock option activities	'
		Years Ended December 31,
		2013					2012					2011
		Number of			Weighted		Number of			Weighted		Number of			Weighted
		shares			Average		shares			Average		shares			Average
		relating			Grant Date		relating			Grant Date		relating			Grant Date
		Restricted			Fair Value		Restricted			Fair Value		Restricted			Fair Value
		Stock Units			Per Unit		Stock Units			Per Unit		Stock Units			Per Unit
	Non-vested at beginning of year		109,275		$	30.5		198,838		$	12.45		198,838		$	12.45
	Granted		—			—		—			—		—			—
	Vested		(87,401	)	$	30.5		(74,537	)	$	30.5		—			—
	Forfeited or expired		(250	)	$	30.5		(15,026	)	$	30.5		—			—
	Non-vested at end of year(1)		21,624		$	30.5		109,275		$	30.5		198,838		$	12.45
	Weighted-average period remaining		—					1 year					2 years
	-1
	For the year ended December 31, 2013, the Company recognized $4.6 million in stock compensation expenses for a probable vesting of 129,611 RSU shares during the first quarter of 2014 based on the performance target achieved from the success of three exploration wells drilled in 2013. The vesting of 129,611 RSU shares in 2014 will exceed the total outstanding RSUs of 21,624 at December 31, 2013 as reported in the above table due to the aggregate payout of 162.5% of the target amount of 198,838 RSUs since inception. Payouts of 37.5%, 50% and 75% of the target amount were approved by the Company's board of directors for each of the three years in the period ended December 31, 2013, totaling 162.5% of the target amount. This is within the range of 0% to 200% vesting percentage of the target amount under the terms of the applicable RSU Award Agreements. Since the vesting of 129,611 RSUs is the final tranche of RSUs vesting under the applicable RSU Award Agreements, there was no unrecognized compensation associated with the RSUs as of December 31, 2013

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
Schedule of components of the income tax provision (benefit)	'
		Year Ended
		December 31,
		2013			2012			2011
		($ in thousands)
	Current taxes:
	U.S. federal	$	—		$	—		$	—
	Foreign		—			—			—
	Deferred taxes:
	U.S. federal		—			—			—
	Foreign		—			—			—
	Total	$	—		$	—		$	—
Schedule of net income pre or post of corporate reorganization	'
		Year Ended December 31,
		2013			2012			2011
		($ in thousands)
	U.S.:
	Net income (loss) as reported	$	(387,210	)	$	(229,372	)	$	(76,231	)
	Less: net income (loss) applicable to period before corporate reorganization		—			—			—
	Foreign:
	Net income (loss) as reported		(201,814	)	$	(53,627	)	$	(57,406	)
	Less: net income (loss) applicable to period before corporate reorganization		—			—			—
	Net income (loss) applicable to period after corporate reorganization	$	(589,024	)	$	(282,999	)	$	(133,637	)
Schedule of effective income tax reconciliation	'
		Year Ended December 31,
		2013						2012					2011
		($ in thousands)
	Income tax expense (benefit) at the federal statutory rate	$	(206,159	)		35	%	$	(99,050	)	35	%	$	(46,773	)	35	%
	State income taxes, net of federal income tax benefit		(489	)		0.1	%		(512	)	0.2	%		(2,579	)	1.9	%
	Foreign income tax		(70,994	)		12.1	%		4,447		-1.6	%		(30,407	)	22.8	%
	Other		366			-0.1	%		2,678		-0.9	%		117		0.1	%
	Valuation allowance(1)		277,276			-47.1	%		92,437		-32.7	%		79,642		59.6	%
		$	—		$	—		$	—		—		$	—		—
	-1
	The change in the deferred tax asset valuation allowance of $277.3 million for the year ended December 31, 2013, excludes a $85.3 million net decrease in valuation allowance due to previously unrecorded foreign deferred tax assets and a deferred tax liability related to the Company's convertible debt instrument that did not impact the rate reconciliation.
Schedule of Company's deferred tax assets and liabilities	'
		As of December 31,
		2013			2012
		($ in thousands)
	Short-term deferred tax liabilities:
	2.625% convertible senior notes due 2019(1)	$	17,061		$	—
	Total short-term deferred tax liabilities		17,061			—
	Long-term deferred tax liabilities:
	2.625% convertible senior notes due 2019	$	103,951		$	—
	Oil and gas properties		22,135			23,867
	Total long-term deferred tax liabilities		126,086			23,867
	Long-term deferred tax assets:
	Seismic and exploration costs		280,095			100,414
	Stock based compensation		20,842			12,340
	Domestic NOL carry forwards		273,163			158,310
	Foreign NOL carry forwards		28,633			20,624
	Other		1,976			1,818
	Valuation allowance		(461,562	)		(269,639	)
	Total long-term deferred assets		143,147			23,867
	Net long-term deferred assets		17,061			—
	Net deferred tax assets	$	—		$	—
	-1
	The recognition of the liability and equity components of the debt resulted in a taxable temporary basis difference and recorded as an adjustment to additional paid-in capital.

Commitments_Tables

Commitments (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments	'
Schedule of payments due for the estimated commitments, excluding long-term debt	'
		Payments Due By Year
		2014		2015		2016		2017		2018		Thereafter
		($ in thousands)
	Drilling Rig and Related Contracts	$	349,000	$	521,000	$	295,000	$	207,000	$	—	$	—
	Operating Leases		13,000		11,000		8,000		5,000		4,000		8,000
	Lease Rentals(1)		6,000		6,000		4,000		3,000		1,000		1,000
	Social Payment Obligations(2)		49,019		50,619		62,854		5,714		5,714		—
	Total	$	417,019	$	588,619	$	369,854	$	220,714	$	10,714	$	9,000
	-1
	Relates to the annual delay rental payments payable to the Office of Natural Resources Revenue within the U.S. Department of the Interior with respect to the Company's U.S. Gulf of Mexico leases. These annual payments are required to maintain the leases from year to year.
	-2
	Includes the Company's contractual payment obligations for social projects such as the Sonangol Research and Technology Center and academic scholarships for Angolan students that the Company was and is contractually obligated to pay in consideration for the Angolan government granting it the licenses to explore for and develop hydrocarbons offshore Angola. Pursuant to the terms of the Risk Services Agreements for Blocks 9 and 21 and the Production Sharing Agreement for Block 20, the Company is not required to pay annual rental payments to maintain the licenses from year to year.

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2013
Segment Information	'
Schedule of segment information by geographic operating segment	'
		United States			West Africa			Total
		($ in thousands)
	Year ended December 31, 2013
	Operating costs and expense	$	329,832		$	202,852		$	532,684
	Operating income (loss)		(329,832	)		(202,852	)		(532,684	)
	Other income (expense)								(56,340	)
	Net income (loss)							$	(589,024	)
	Additions to Property and Equipment, net(1)	$	44,124		$	332,395		$	376,519
	Year ended December 31, 2012
	Operating costs and expense	$	231,196		$	53,632		$	284,828
	Operating income (loss)		(231,196	)		(53,632	)		(284,828	)
	Other income (expense)								1,829
	Net income (loss)							$	(282,999	)
	Additions to Property and Equipment, net(1)	$	67,068		$	169,362		$	236,430
	Year ended December 31, 2011
	Operating costs and expense	$	80,425		$	57,411		$	137,836
	Operating income (loss)		(80,425	)		(57,411	)		(137,836	)
	Other income (expense)								4,199
	Net income (loss)							$	(133,637	)
	Additions to Property and Equipment, net(1)	$	(12,324	)	$	411,882		$	399,558
	-1
	These amounts are net of accumulated allowance for impairment on oil and gas properties and accumulated depreciation and amortization on other property and equipment.

Selected_Quarterly_Financial_D1

Selected Quarterly Financial Data-Unaudited (Tables)	12 Months Ended
	Dec. 31, 2013
Selected Quarterly Financial Data-Unaudited	'
Schedule of Selected Quarterly Financial Data Unaudited	'
		1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
		($ in thousands)
	Year ended December 31, 2013
	Operating costs and expenses	$	112,452		$	65,365		$	145,663		$	209,204
	Operating income (loss)		(112,452	)		(65,365	)		(145,663	)		(209,204	)
	Net income (loss)		(128,087	)		(78,818	)		(160,000	)		(222,119	)
	Basic and diluted income (loss) per common share(1)	$	(0.31	)	$	(0.19	)	$	(0.39	)	$	(0.55	)
	Year ended December 31, 2012
	Operating costs and expenses	$	37,715		$	142,155		$	40,553		$	64,405
	Operating income (loss)		(37,715	)		(142,155	)		(40,553	)		(64,405	)
	Net income (loss)		(36,531	)		(140,723	)		(39,214	)		(66,531	)
	Basic and diluted income (loss) per common share(1)	$	(0.09	)	$	(0.35	)	$	(0.10	)	$	(0.16	)
	-1
	Totals may not add due to rounding.

Supplemental_Information_on_Oi1

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited)	'
Schedule of Capitalized Costs Related to Oil and Gas Activities	'
		U.S. Gulf			West Africa		Total
		of Mexico
		($ in thousands)
	As of December 31, 2013
	Unproved properties(1)	$	605,658		$	927,059	$	1,532,717
	Accumulated valuation allowance		(160,913	)		—		(160,913	)
			444,745			927,059		1,371,804
	Proved properties		92,579			—		92,579
	Net capitalized costs	$	537,324		$	927,059	$	1,464,383
	As of December 31, 2012
	Unproved properties	$	572,257		$	600,620	$	1,172,877
	Accumulated valuation allowance		(78,413	)		—		(78,413	)
			493,844			600,620		1,094,464
	Proved properties		—			—		—
	Net capitalized costs	$	493,844		$	600,620	$	1,094,464
	-1
	Unproved properties include capitalized costs net of sale/like-kind exchange of leasehold interest transactions that occurred in 2013 and 2012 of approximately $10.7 million and $0.8 million, respectively, for the U.S. Gulf of Mexico. No gain or loss was recognized for these transactions for the years ended December 31, 2013 and 2012.
Schedule of Costs Incurred in Oil and Gas Activities	'
		U.S. Gulf			West Africa		Total
		of Mexico
		($ in thousands)
	Year ended December 31, 2013
	Property acquisition
	Unproved	$	37,584		$	—	$	37,584
	Proved		—			—		—
	Exploration
	Capitalized		158,806			469,879		628,685
	Expensed		48,688			25,525		74,213
	Development		54,133			—		54,133
	Total Costs Incurred	$	299,211		$	495,404	$	794,615
	Year ended December 31, 2012
	Property acquisition
	Unproved	$	19,961		$	—	$	19,961
	Proved		—			—		—
	Exploration
	Capitalized		178,295			168,309		346,604
	Expensed		32,874			28,709		61,583
	Development		—			—		—
	Total Costs Incurred	$	231,130		$	197,018	$	428,148
	Year ended December 31, 2011
	Property acquisition
	Unproved	$	—		$	337,126	$	337,126
	Proved		—			—		—
	Exploration
	Capitalized		11,214			96,849		108,063
	Expensed		10,707			21,532		32,239
	Development		—			—		—
	Total Costs Incurred	$	21,921		$	455,507	$	477,428
Schedule of reserve quantity information	'
		Natural Gas			Oil and		Equivalent
		(in Bcf)			Condensate		Volumes
					(in MMBbls)		(in MMBOE)
	Proved undeveloped reserves:
	Beginning of year		—
	Discoveries		3.4			7.9		8.5
	End of year		3.4			7.9		8.5
Schedule of the Company's estimated discounted future net cash flows related to its proved natural gas reserves	'
	Information with respect to the Company's estimated discounted future net cash flows related to its proved natural gas reserves as of December 31, 2013 is as follows ($ in thousands):
		2013
	Future cash inflows	$	830,287
	Future production costs		(6,400	)
	Future development costs		(302,278	)
	Future income tax expense(1)		—
	Future net cash flows		521,609
	10% annual discount for estimated timing of cash flows		(244,976	)
	Standardized measure of discounted future net cash flows	$	276,633
	-1
	There is no future income tax expense as of December 31, 2013, as the tax basis of the oil and gas properties in the United States and net operating losses attributable to oil and gas operations exceed the future net revenues.
Schedule of information with respect to the company's standardized measure of discounted future net cash flows	'
	Information with respect to the Company's standardized measure of discounted future net cash flows as of December 31, 2013 is as follows ($ in thousands):
		2013
	Standardized measure, beginning	$	—
	Discoveries		276,633
	Standardized measure, ending	$	276,633

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended			98 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 17, 2012
					2.625% convertible senior notes due 2019	2.625% convertible senior notes due 2019	2.625% convertible senior notes due 2019
Revenue Recognition	'	'	'	'	'	'	'
Oil and gas revenue	$0	$0	$0	$0	'	'	'
Investments	'	'	'	'	'	'	'
OTTI in debt securities	$0	$0	'	$0	'	'	'
Joint Interest and Other Receivables	'	'	'	'	'	'	'
Settlement period of receivables, maximum	'30 days	'	'	'	'	'	'
Earnings (Loss) Per Share	'	'	'	'	'	'	'
Shares of non-vested restricted stock, non vested restricted stock units, outstanding stock options and 2.625% convertible senior notes due 2019 excluded from the diluted income (loss) per share calculation	6,735,046	5,617,697	'	'	'	'	'
Earnings (Loss) Per Share	'	'	'	'	'	'	'
Interest rate (as a percent)	'	2.63%	'	'	2.63%	2.63%	2.63%

Cash_and_Cash_Equivalents_Deta

Cash and Cash Equivalents (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Cash and Cash Equivalents	'	'	'	'
Cash at banks	$82,428	$65,935	'	'
Money market funds	75,039	1,105,148	'	'
Held-to-maturity securities	34,993	254,732	'	'
Total	$192,460	$1,425,815	$292,546	$302,720

Restricted_Funds_Details

Restricted Funds (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2009	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2013
			Block 9, offshore Angola	Ensco 8503 escrow account	Ensco 8503 escrow account	Collateral on letters of credit for Angola	Collateral on letters of credit for Angola	Collateral on letters of credit for Angola	Other vendor restricted deposits	Cash collateral associated with work program obligations which have been completed	Cash collateral associated with work program obligations which have not been completed
								U.S. Treasury bills
Restricted Funds	'	'	'	'	'	'	'	'	'	'	'
Short-term restricted funds	$200,339,000	$90,440,000	'	$90,440,000	$180,900,000	$200,339,000	'	'	'	$153,600,000	$46,700,000
Long-term restricted funds	104,496,000	395,652,000	'	90,440,000	180,900,000	104,496,000	304,492,000	'	720,000	'	'
Collateral held	'	'	'	'	'	304,800,000	304,500,000	'	'	'	'
Net carrying value of investments invested through the funds	'	'	'	'	'	'	'	304,800,000	'	'	'
Maturity period of investments	'	'	'	'	'	'1 year	'	'	'	'	'
Work program obligations secured	'	'	$45,300,000	'	'	'	'	'	'	'	'

Joint_Interests_and_Other_Rece2

Joint Interests and Other Receivables (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Joint Interest Receivables	'	'
Accrued interest on investment securities	$5,632,000	$3,647,000
Other	3,446,000	3,321,000
Total	124,639,000	61,592,000
Partners in the U.S. Gulf of Mexico	'	'
Joint Interest Receivables	'	'
Receivable attributable to joint interest partners	68,664,000	52,439,000
Partners in West Africa	'	'
Joint Interest Receivables	'	'
Receivable attributable to joint interest partners	46,897,000	2,185,000
Partners in West Africa | Block 20, offshore Angola	'	'
Joint Interest Receivables	'	'
Receivable attributable to joint interest partners	15,700,000	'
Partners in West Africa | Blocks 9 and 21 offshore Angola	'	'
Joint Interest Receivables	'	'
Joint interest and other receivables which became past due	$31,200,000	'

Prepaid_Expenses_and_Other_Cur2

Prepaid Expenses and Other Current Assets (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Prepaid expenses:	'	'
Prepaid expenses	$37,796,000	$11,729,000
Other current assets:	'	'
Cash advance to joint venture partner	9,685,000	351,000
Rig mobilization, regulatory and other related costs	8,376,000	11,861,000
Prepaid expenses and other current assets	55,857,000	23,941,000
Unamortized portion of payments made for software licenses included in prepaid expenses	11,500,000	'
Costs associated with Ensco drilling rig contract included in prepaid expenses	$26,300,000	'

Investments_Details

Investments (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments	'	'
Fair market value	$1,673,869	$1,564,441
Held-to-maturities, Amortized Cost	'	'
Within 1 year	1,659,208	1,528,174
After 1 year	14,661	36,267
Total	1,673,869	1,564,441
Held-to-maturity securities, Estimated fair value	'	'
Within 1 year	1,659,208	1,528,174
After 1 year	14,661	36,267
Total	1,673,869	1,564,441
Cash and cash equivalents	'	'
Investments	'	'
Fair market value	34,993	254,732
Held-to-maturity securities, Estimated fair value	'	'
Total	34,993	254,732
Short-term investments	'	'
Investments	'	'
Fair market value	1,319,380	789,668
Held-to-maturity securities, Estimated fair value	'	'
Total	1,319,380	789,668
Short-term restricted funds	'	'
Investments	'	'
Fair market value	200,339	90,440
Held-to-maturity securities, Estimated fair value	'	'
Total	200,339	90,440
Long-term restricted funds	'	'
Investments	'	'
Fair market value	104,496	393,334
Held-to-maturity securities, Estimated fair value	'	'
Total	104,496	393,334
Long-term investments	'	'
Investments	'	'
Fair market value	14,661	36,267
Held-to-maturity securities, Estimated fair value	'	'
Total	14,661	36,267
U.S. Treasury securities	'	'
Investments	'	'
Fair market value	304,834	483,775
Held-to-maturity securities, Estimated fair value	'	'
Total	304,834	483,775
Corporate securities	'	'
Investments	'	'
Fair market value	856,002	510,691
Held-to-maturity securities, Estimated fair value	'	'
Total	856,002	510,691
Commercial paper	'	'
Investments	'	'
Fair market value	408,033	562,975
Held-to-maturity securities, Estimated fair value	'	'
Total	408,033	562,975
Certificates of deposit	'	'
Investments	'	'
Fair market value	105,000	7,000
Held-to-maturity securities, Estimated fair value	'	'
Total	$105,000	$7,000

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	$192,460	$1,425,815	$292,546	$302,720
Short-term restricted funds	200,339	90,440	'	'
Short-term investments	1,319,380	789,668	'	'
Long-term restricted funds	104,496	395,652	'	'
Long-term investments	14,661	36,267	'	'
Total	1,831,336	2,737,842	'	'
Cash | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	82,428	65,935	'	'
Money market funds | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	75,039	1,105,148	'	'
Long-term restricted funds	'	2,318	'	'
Commercial paper | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	9,993	247,206	'	'
Short-term investments	391,073	315,769	'	'
Long-term investments	6,967	'	'	'
Corporate bonds | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	'	7,526	'	'
Short-term investments	848,307	466,898	'	'
Long-term investments	7,694	36,267	'	'
U.S. Treasury bills | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term restricted funds	'	90,440	'	'
Long-term restricted funds	'	178,216	'	'
U.S. Treasury notes | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term restricted funds	200,339	'	'	'
Long-term restricted funds	104,496	215,118	'	'
Certificates of deposits | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	25,000	'	'	'
Short-term investments	80,000	7,001	'	'
Level 1 | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	157,467	1,171,083	'	'
Long-term restricted funds	'	2,318	'	'
Total	157,467	1,173,401	'	'
Level 1 | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	157,467	1,171,083	'	'
Long-term restricted funds	'	2,318	'	'
Total	157,467	1,173,401	'	'
Level 1 | Cash | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	82,428	65,935	'	'
Level 1 | Cash | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	82,428	65,935	'	'
Level 1 | Money market funds | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	75,039	1,105,148	'	'
Long-term restricted funds	'	2,318	'	'
Level 1 | Money market funds | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	75,039	1,105,148	'	'
Long-term restricted funds	'	2,318	'	'
Level 2 | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	34,993	254,732	'	'
Short-term restricted funds	200,339	90,440	'	'
Short-term investments	1,319,380	789,668	'	'
Long-term restricted funds	104,496	393,334	'	'
Long-term investments	14,661	36,267	'	'
Total	1,673,869	1,564,441	'	'
Level 2 | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	34,993	254,732	'	'
Short-term restricted funds	200,339	90,440	'	'
Short-term investments	1,319,380	789,668	'	'
Long-term restricted funds	104,496	393,334	'	'
Long-term investments	14,661	36,267	'	'
Total	1,673,869	1,564,441	'	'
Level 2 | Commercial paper | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	9,993	247,206	'	'
Short-term investments	391,073	315,769	'	'
Long-term investments	6,967	'	'	'
Level 2 | Commercial paper | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	9,993	247,206	'	'
Short-term investments	391,073	315,769	'	'
Long-term investments	6,967	'	'	'
Level 2 | Corporate bonds | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	'	7,526	'	'
Short-term investments	848,307	466,898	'	'
Long-term investments	7,694	36,267	'	'
Level 2 | Corporate bonds | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	'	7,526	'	'
Short-term investments	848,307	466,898	'	'
Long-term investments	7,694	36,267	'	'
Level 2 | U.S. Treasury bills | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term restricted funds	'	90,440	'	'
Long-term restricted funds	'	178,216	'	'
Level 2 | U.S. Treasury bills | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term restricted funds	'	90,440	'	'
Long-term restricted funds	'	178,216	'	'
Level 2 | U.S. Treasury notes | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term restricted funds	200,339	'	'	'
Long-term restricted funds	104,496	215,118	'	'
Level 2 | U.S. Treasury notes | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term restricted funds	200,339	'	'	'
Long-term restricted funds	104,496	215,118	'	'
Level 2 | Certificates of deposits | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	25,000	'	'	'
Short-term investments	80,000	7,001	'	'
Level 2 | Certificates of deposits | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	25,000	'	'	'
Short-term investments	$80,000	$7,001	'	'

Property_Plant_and_Equipment_D

Property, Plant, and Equipment (Details) (USD $)

12 Months Ended

98 Months Ended

12 Months Ended

98 Months Ended

0 Months Ended

1 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Feb. 26, 2013

Sep. 30, 2013

Dec. 31, 2013

Dec. 20, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Exploration well costs

Well development costs

Block 9, offshore Angola

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Oil and gas properties, net

Exploration wells in process

Exploration wells in process

Computer equipment and software

Computer equipment and software

Office equipment and furniture

Office equipment and furniture

Office equipment and furniture

Office equipment and furniture

Vehicles

Vehicles

Leasehold improvements

Leasehold improvements

Leasehold improvements

Leasehold improvements

Running tools and equipment

Mississippi Canyon Block 209

Mississippi Canyon Block 209

Mississippi Canyon Block 209

Block 20 offshore Angola

Block 20 offshore Angola

Blocks 9 and 21 offshore Angola and Gabon

Blocks 9 and 21 offshore Angola

Diaba Block offshore Gabon

U.S. Gulf of Mexico

Garden Banks Block 822, Mississippi Canyon Block 605 and Walker Ridge Block 232

Minimum

Maximum

Minimum

Maximum

Property, Plant, and Equipment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimated Useful Life

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'3 years

'

'

'

'3 years

'5 years

'3 years

'

'

'

'3 years

'10 years

'3 years

Well and development costs

$92,579,000

'

'

$92,579,000

$31,600,000

$61,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total proved properties

92,579,000

'

'

92,579,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Oil and gas leasehold

754,894,000

721,853,000

'

754,894,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Less: accumulated valuation allowance

-160,913,000

-78,413,000

'

-160,913,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unproved leasehold properties

593,981,000

643,440,000

'

593,981,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total unproved leasehold properties

1,371,804,000

1,094,464,000

'

1,371,804,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

777,823,000

451,024,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Total oil and gas properties, net

1,464,383,000

1,094,464,000

'

1,464,383,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property, plant, and equipment, gross

16,286,000

7,825,000

'

16,286,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,115,000

3,166,000

2,132,000

2,093,000

'

'

265,000

268,000

2,456,000

2,298,000

'

'

6,318,000

Less: accumulated depreciation and amortization

-4,394,000

-2,533,000

'

-4,394,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total other property and equipment

11,892,000

5,292,000

'

11,892,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total property, plant, and equipment, net

1,476,275,000

1,099,756,000

'

1,476,275,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Old computer equipment and leasehold improvements written off during the period

'

2,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Depreciation and amortization

1,874,000

1,197,000

735,000

6,626,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of working interest acquired

'

'

'

'

'

'

'

'

'

'

'

'

'

'

40.00%

'

'

40.00%

21.25%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Consideration for the acquisition

'

'

'

'

'

'

'

'

'

'

'

'

'

'

347,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Consideration payable over five years on acquisition

'

'

'

'

'

'

'

'

'

'

'

'

'

'

337,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Period over which consideration is payable

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Consideration paid on acquisition

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

165,700,000

'

'

'

'

37,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected impairment charges

'

'

'

'

'

'

2,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Acquisition costs relinquished

'

'

'

'

'

'

45,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Short-term and long-term contractual obligations

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

171,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unproved

37,584,000

19,961,000

337,126,000

'

'

'

'

'

'

'

'

'

'

'

'

'

10,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unproved property acquisition costs, net of valuation allowance, relating to properties offshore

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

236,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total consideration for the sale

'

'

'

'

'

'

'

'

'

'

'

5,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Consideration for the sale received at closing date

'

'

'

'

'

'

'

'

'

'

'

1,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Additional consideration for the sale receivable on commencement of operations

'

'

'

'

'

'

'

'

'

'

'

'

1,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Contingent consideration for the sale to be receivable on commencement of production

'

'

'

'

'

'

'

'

'

'

'

2,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain on sale of assets

2,993,000

'

'

2,993,000

'

'

'

'

'

'

'

'

'

3,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Lower limit of unproved leasehold costs assessed individually for impairment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Upper limit of unproved leasehold costs on individual properties included in group amortization

'

'

'

'

'

'

'

1,000,000

'

'

1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Carrying amount of unproved properties subject to amortization before impairment provision

'

'

'

'

'

'

'

68,900,000

69,100,000

'

68,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Lease impairment allowance

'

'

'

'

'

'

'

$87,000,000

$60,200,000

$9,100,000

$165,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property_Plant_and_Equipment_D1

Property, Plant, and Equipment (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Beginning of period	$451,024	$178,338	$106,881
Reclassification to wells, facilities, and equipment based on determination of proved reserves	-38,446	'	'
Amounts charged to expense	-263,439	-73,918	-36,606
End of period	777,823	451,024	178,338
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Cumulative costs	777,823	451,024	178,338
Well costs capitalized for a period greater than one year after completion of drilling	399,775	194,853	'
Exploration well costs | Offshore Gabon	'	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Amounts charged to expense	-17,100	'	'
Exploration well costs | Offshore Angola	'	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Amounts charged to expense	-126,300	'	'
U.S. Gulf of Mexico | Exploration well costs	'	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Beginning of period	208,275	'	'
Additions to capitalized exploration	154,877	178,295	11,214
Amounts charged to expense	-120,000	'	'
End of period	204,707	208,275	'
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Cumulative costs	204,707	208,275	'
U.S. Gulf of Mexico | Capitalized interest	'	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Additions to capitalized exploration	3,928	'	'
End of period	3,928	'	'
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Cumulative costs	3,928	'	'
West Africa | Exploration well costs	'	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Beginning of period	242,749	'	'
Additions to capitalized exploration	457,608	168,309	96,849
End of period	556,917	242,749	'
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Cumulative costs	556,917	242,749	'
West Africa | Capitalized interest	'	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Additions to capitalized exploration	12,271	'	'
End of period	12,271	'	'
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'	'
Cumulative costs	$12,271	'	'

Other_Assets_Details

Other Assets (Details) (USD $)	0 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 17, 2012	Dec. 31, 2013	Dec. 31, 2012
Other Assets	'	'	'
Debt issue cost	'	$20,983	$23,042
Long-term portion of prepaid shorebase leases	'	3,241	'
Rig mobilization costs	'	11,153	'
Long-term accounts receivable	'	17,923	'
Other	'	437	'
Other assets	'	53,737	23,042
Interest rate (as a percent)	'	'	2.63%
Blocks 9 and 21 offshore Angola	'	'	'
Other Assets	'	'	'
Long-term accounts receivable	'	17,900	'
Percentage of paying interest due from related parties	'	3.75%	'
Notes	'	'	'
Other Assets	'	'	'
Debt issue cost	$32,200	$21,000	$23,000
Interest rate (as a percent)	2.63%	2.63%	2.63%

Longterm_Debt_Details

Long-term Debt (Details) (USD $)	12 Months Ended		98 Months Ended	0 Months Ended	12 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 17, 2012	Dec. 31, 2013	Dec. 31, 2012
				Notes	Notes	Notes
Debt instrument	'	'	'	'	'	'
Aggregate principal amount of notes issued	'	'	'	$1,380,000,000	'	'
Interest rate (as a percent)	'	2.63%	'	2.63%	2.63%	2.63%
Interest paid	34,615,000	'	34,615,000	'	34,600,000	'
Initial conversion rate of common stock	'	'	'	0.028023	'	'
Initial conversion price per share of common stock (in dollars per share)	'	'	'	$35.68	'	'
Number of underlying shares that the holder of the debt instrument would receive upon conversion	'	'	'	38.7	'	'
Repurchase price as a percentage of principal amount of debt instrument	'	'	'	100.00%	'	'
Specified minimum percentage of principal amount, the holders of which may declare all principal, accrued and unpaid interest to be due and payable immediately, upon the occurrence of an Event of Default	'	'	'	25.00%	'	'
Percentage of principal amount, which may be declared by holders of a specified principal amount to be due and payable immediately upon occurrence of an Event of Default	'	'	'	100.00%	'	'
Fair value of the notes excluding conversion feature at the date of issuance	'	'	'	989,500,000	'	'
Effective interest rate used to amortize liability component of debt issue costs (as a percent)	'	'	'	8.40%	'	'
Debt issue cost	20,983,000	23,042,000	'	32,200,000	21,000,000	23,000,000
Debt issue cost allocated to the liability component	'	'	'	23,100,000	'	'
Debt issue cost allocated to the equity component	'	'	'	9,100,000	9,124,000	9,124,000
Carrying amounts of the liability components	'	'	'	'	'	'
Principal Amount	'	'	'	'	1,380,000,000	1,380,000,000
Unamortized discount	'	'	'	'	-344,020,000	-388,809,000
Carrying amount of the liability components	1,035,980,000	991,191,000	1,035,980,000	'	1,035,980,000	991,191,000
Remaining term of debt	'	'	'	'	'6 years	'
Carrying amounts of the equity components	'	'	'	'	'	'
Debt discount relating to value of conversion option	'	'	'	'	390,540,000	390,540,000
Debt issue costs	'	'	'	-9,100,000	-9,124,000	-9,124,000
Carrying amount of the equity components	'	'	'	'	381,416,000	381,416,000
Fair value of the notes excluding conversion feature	'	'	'	'	$1,227,100,000	$989,500,000

Longterm_Debt_Details_2

Long-term Debt (Details 2) (2.625% convertible senior notes due 2019, USD $)	12 Months Ended		98 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013
2.625% convertible senior notes due 2019	'	'	'
Debt instrument	'	'	'
Interest expense associated with accrued interest	$18,529,000	$1,294,000	$19,823,000
Interest expense associated with accretion of debt discount	44,789,000	1,843,000	46,632,000
Interest expense associated with amortization of debt issue costs	2,058,000	75,000	2,133,000
Total	65,376,000	3,212,000	68,588,000
Capitalized interest costs	$17,700,000	$0	'

Contractual_Obligations_Detail

Contractual Obligations (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2014
			Block 9, offshore Angola	Block 9, offshore Angola	Block 21, offshore Angola	Block 21, offshore Angola	Block 20, offshore Angola	Block 20, offshore Angola	Block 20, offshore Angola
									Subsequent event
Contractual obligations	'	'	'	'	'	'	'	'	'
Short-term Contractual Obligations: Social obligation payments	$49,019,000	$49,019,000	$150,000	$150,000	$300,000	$300,000	$48,569,000	$48,569,000	'
Long-term Contractual Obligations: Social obligation payments	124,901,000	168,238,000	669,000	848,000	1,381,000	1,684,000	122,851,000	165,706,000	'
Payment of short-term contractual obligation	'	'	'	'	'	'	'	'	$42,900,000

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Feb. 29, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 17, 2012	Jan. 15, 2012
				Notes	Notes	Notes	Deferred Compensation Plan
Stockholders' Equity	'	'	'	'	'	'	'
Common stock, shares issued	406,949,839	406,596,884	18,050,000	'	'	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01	$28	'	'	'	'
Equity based Compensation	'	'	'	'	'	'	'
Aggregate number of shares withheld to satisfy tax withholding obligations of employees relating to equity based compensation	'	'	'	'	'	'	9,127
Stock price of shares withheld to satisfy tax withholding obligations of employees relating to equity based compensation (in dollars per share)	'	'	'	'	'	'	$18.74
Aggregate principal amount of notes issued	'	'	'	'	'	$1,380,000,000	'
Interest rate (as a percent)	'	2.63%	'	2.63%	2.63%	2.63%	'
Carrying amount of the equity components	'	'	'	$381,416,000	$381,416,000	'	'

Seismic_and_Exploration_Expens2

Seismic and Exploration Expenses (Details) (USD $)	12 Months Ended			98 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Seismic and Exploration Expenses	'	'	'	'
Seismic costs	$63,721	$42,447	$20,443	$405,769
Seismic cost recovery	'	'	'	-25,126
Leasehold delay rentals	6,660	6,383	6,075	39,562
Force Majeure expense	'	'	'	13,549
Drilling rig expense	3,832	12,753	5,721	30,631
Total seismic and exploration expenses	$74,213	$61,583	$32,239	$464,385

Equity_based_Compensation_Deta

Equity based Compensation (Details) (USD $)

12 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

item

Incentive Plan

NED Plan

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock

Retainer awards

Retainer awards

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Non-employee directors

Non-employee directors

Non-employee directors

Minimum

Maximum

Period one

Period two

Period three

Forecast

Non-employee directors

Common Stock

Common Stock

Subsequent event

Equity based Compensation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares available for grant under the plan

'

7,500,000

500,158

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Restricted Shares

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Non-vested shares at beginning of the period

'

'

'

4,040,825

4,599,783

5,570,895

'

'

'

109,275

198,838

198,838

'

'

'

'

'

'

'

Granted (in shares)

'

'

'

620,840

487,710

214,792

'

'

'

'

'

'

'

'

'

'

'

'

'

Vested (in shares)

'

'

'

-239,317

-738,628

-1,185,904

'

'

'

-87,401

-74,537

'

'

'

'

'

'

-129,611

'

Forfeited or expired (in shares)

'

'

'

-87,462

-308,040

'

'

'

'

-250

-15,026

'

'

'

'

'

'

'

'

Non-vested shares at end of the period

'

'

'

4,334,886

4,040,825

4,599,783

'

'

'

21,624

109,275

198,838

'

'

'

'

'

'

'

Weighted Average Grant Date Fair Value Per Share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Non-vested shares at beginning of the period (in dollars per share)

'

'

'

$13.05

$11.27

$9.77

'

'

'

$30.50

$12.45

$12.45

'

'

'

'

'

'

'

Granted (in dollars per share)

'

'

'

$24.58

$26.01

$8.54

'

'

'

'

'

'

'

'

'

'

'

'

'

Vested (in dollars per share)

'

'

'

$17.37

$13.05

$3.75

'

'

'

$30.50

$30.50

'

'

'

'

'

'

'

'

Forfeited or expired (in dollars per share)

'

'

'

$20.91

$12.17

'

'

'

'

$30.50

$30.50

'

'

'

'

'

'

'

'

Non-vested shares at end of the period (in dollars per share)

'

'

'

$14.31

$13.05

$11.27

'

'

'

$30.50

$30.50

$12.45

'

'

'

'

'

'

'

Weighted-average vesting period remaining

'

'

'

'1 year 2 months 19 days

'1 year 10 months 13 days

'2 years 6 months

'

'

'

'

'1 year

'2 years

'

'

'

'

'

'

'

Compensation expenses for probable vesting of performance based units

'

'

'

$4,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of exploration wells drilled

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payout percentage

'

'

'

'

'

'

'

'

'

162.50%

'

'

0.00%

200.00%

37.50%

50.00%

75.00%

'

'

Unrecognized compensation

'

'

'

$22,467,000

$23,827,000

$29,559,000

'

'

'

$0

'

'

'

'

'

'

'

'

'

Awards granted (in shares)

'

'

'

'

'

'

'

15,318

12,221

'

'

'

'

'

'

'

'

'

39,818

Awards granted as on period end (in shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

177,763

Weighted average fair value of shares at grant date (in dollars per share)

'

'

'

'

'

'

$25.40

'

'

$12.45

'

'

'

'

'

'

'

'

'

Equity_based_Compensation_Deta1

Equity based Compensation (Details 2) (Non-Qualified Stock Options, USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Equity based Compensation	'	'
Contractual term for options granted	'10 years	'
Vesting period	'4 years	'
Assumptions used to determine the fair value of each stock option granted using the Black-Scholes-Merton option-pricing model	'	'
Expected Term in Years	'6 years 8 months 5 days	'
Expected Volatility (as a percent)	61.58%	'
Expected Dividends (as a percent)	0.00%	'
Risk-Free Interest Rate (as a percent)	1.28%	'
Number of Stock Options	'	'
Outstanding at the beginning of the period (in shares)	1,434,393	'
Granted (in shares)	959,023	'
Exercised (in shares)	-13,985	'
Forfeited or expired (in shares)	-40,713	'
Outstanding at the end of the period (in shares)	2,338,718	1,434,393
Vested or expected to vest at the end of the period (in shares)	1,568,748	'
Exercisable at the end of the period (in shares)	737,973	'
Weighted Average Exercise Price	'	'
Outstanding at the beginning of the period (in dollars per share)	$17.87	'
Granted (in dollars per share)	$23.78	'
Exercised (in dollars per share)	$12.45	'
Forfeited or expired (in dollars per share)	$22.89	'
Outstanding at the end of the period (in dollars per share)	$20.24	$17.87
Vested or expected to vest at the end of the period (in dollars per share)	$23.83	'
Exercisable at the end of the period (in dollars per share)	$12.45	'
Weighted-Average Remaining Contractual Term (in years)	'	'
Outstanding at the beginning of the period	'8 years	'8 years 3 months 18 days
Granted	'9 years 1 month 6 days	'
Exercised	'6 years 10 months 24 days	'
Outstanding at the end of the period	'8 years	'8 years 3 months 18 days
Vested or expected to vest at the end of the period	'8 years 6 months	'
Exercisable at the end of the period	'6 years 10 months 24 days	'
Weighted-average grant-date fair value of stock options granted (in dollars per share) using the Black-Scholes option-pricing model	$14.08	$17.92
Unrecognized compensation cost	$14,000	'
Period for recognition of unrecognized compensation cost	'2 years 1 month 24 days	'
Aggregate Intrinsic Value	'	'
Outstanding at the beginning of the period	12,158	'
Exercised	219	'
Outstanding at the end of the period	3,937	12,158
Vested or expected to vest at the end of the period	965	'
Exercisable at the end of the period	$2,952	'
31-Dec-15	'	'
Equity based Compensation	'	'
Vesting percentage	50.00%	'
31-Dec-16	'	'
Equity based Compensation	'	'
Vesting percentage	50.00%	'

Equity_based_Compensation_Deta2

Equity based Compensation (Details 3) (USD $)

12 Months Ended

98 Months Ended

12 Months Ended

98 Months Ended

12 Months Ended

98 Months Ended

0 Months Ended

12 Months Ended

98 Months Ended

12 Months Ended

98 Months Ended

In Thousands, except Share data, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 03, 2010

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Deferred stock compensation

Stock options

Stock options

Stock options

Stock options

Stock options

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted stock units (performance-based)

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock

Employees

Employees

Employees

Employees

Employees

Non-employee directors

Minimum

Maximum

Employees

Employees

Employees

Employees

Non-employee directors

Non-employee directors

Non-employee directors

Non-employee directors

Equity based Compensation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Granted during the period (in shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

198,838

39,818

'

'

'

'

'

'

'

'

'

'

Vesting period

'

'

'

'

'

'4 years

'

'

'

'

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting percentage

'

'

'

'

'

'

'

'

'

'

162.50%

'

'

'

'

0.00%

200.00%

'

'

'

'

'

'

'

'

Shares authorized under the plan

'

'

'

'

'

'

'

'

'

'

397,676

'

397,676

'

'

'

'

'

'

'

'

'

'

'

'

Multiplier to determine awards vested (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

37.50%

'

'

'

'

'

'

'

'

Closing price of the entity's common stock at the date of grant (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$12.45

'

'

'

'

'

'

'

'

'

'

$25.40

'

'

'

Equity-based compensation costs

$28,754

$22,410

$15,505

$89,461

$1,828

'

$7,405

$3,790

$1,841

$13,137

$4,619

$4,272

$8,891

'

'

'

'

$15,470

$13,378

$12,860

$62,064

$1,260

$970

$804

$3,541

Employee_Benefit_Plan_Details

Employee Benefit Plan (Details) (USD $)	12 Months Ended				98 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2006	Dec. 31, 2013
Employee Benefit Plan	'	'	'	'	'
Minimum period following date of hire after which employees become eligible to participate in the Plan	'	'	'	'3 months	'
Employee contribution match in plan (as a percent)	'	'	'	6.00%	'
Expenses recorded in benefit contributions to the Plan	$0.80	$0.50	$0	'	$2.80

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended			98 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Income Taxes	'	'	'	'
Net deferred tax asset	$461,600,000	$269,600,000	$177,200,000	$461,600,000
Valuation allowance	461,562,000	269,639,000	177,200,000	461,562,000
U.S.:	'	'	'	'
Net income (loss) as reported	-387,210,000	-229,372,000	-76,231,000	'
Foreign:	'	'	'	'
Net income (loss) as reported	-201,814,000	-53,627,000	-57,406,000	'
Net income (loss) before income tax	($589,024,000)	($282,999,000)	($133,637,000)	($1,516,859,000)

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of income taxes computed at the U.S. federal statutory tax rate to the Company's income tax expense (benefit)	'	'	'
Income tax expense (benefit) at the federal statutory rate	($206,159,000)	($99,050,000)	($46,773,000)
State income taxes, net of federal income tax benefit	-489,000	-512,000	-2,579,000
Foreign income taxes	-70,994,000	4,447,000	-30,407,000
Other	366,000	2,678,000	117,000
Valuation allowance	277,276,000	92,437,000	79,642,000
Total	0	0	0
Reconciliation of income taxes computed at the U.S. federal statutory tax rate to the Company's income tax expense (benefit)	'	'	'
Income tax expense (benefit) at the federal statutory rate (as a percent)	35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit (as a percent)	0.10%	0.20%	1.90%
Foreign income taxes (as a percent)	12.10%	-1.60%	22.80%
Other (as a percent)	-0.10%	-0.90%	0.10%
Valuation allowance (as a percent)	-47.10%	-32.70%	59.60%
Amount of previously unrecorded foreign deferred tax assets and deferred tax liability related to convertible debt excluded from the change in deferred tax asset valuation allowance	$85,300,000	'	'

Income_Taxes_Details_3

Income Taxes (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Short-term deferred tax liabilities:	'	'	'
2.625% convertible senior notes due 2019	$17,061,000	'	'
Total short-term deferred tax liabilities	17,061,000	'	'
Long-term deferred tax liabilities:	'	'	'
2.625% convertible senior notes due 2019	103,951,000	'	'
Oil and gas properties	22,135,000	23,867,000	'
Total long-term deferred tax liabilities	126,086,000	23,867,000	'
Long-term deferred tax assets:	'	'	'
Seismic and exploration costs	280,095,000	100,414,000	'
Stock-based compensation	20,842,000	12,340,000	'
Domestic NOL carry forwards	273,163,000	158,310,000	'
Foreign NOL carry forwards	28,633,000	20,624,000	'
Other	1,976,000	1,818,000	'
Valuation allowance	-461,562,000	-269,639,000	-177,200,000
Total long-term deferred assets	143,147,000	23,867,000	'
Net long-term deferred assets	17,061,000	'	'
Income tax expense or benefit	0	0	0
Income Taxes	'	'	'
Unrecognized tax benefits	0	0	'
Accrued interest or penalties associated with unrecognized tax benefits	0	0	'
Federal	'	'	'
Income Taxes	'	'	'
Net operating loss carryforwards	787,200,000	'	'
State	'	'	'
Income Taxes	'	'	'
Net operating loss carryforwards	51,900,000	'	'
Foreign	'	'	'
Income Taxes	'	'	'
Net operating loss carryforwards	$54,400,000	'	'

Commitments_Details

Commitments (Details) (USD $)	12 Months Ended			98 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Contractual obligation and commitments	'	'	'	'
2014	$417,019,000	'	'	$417,019,000
2015	588,619,000	'	'	588,619,000
2016	369,854,000	'	'	369,854,000
2017	220,714,000	'	'	220,714,000
2018	10,714,000	'	'	10,714,000
Thereafter	9,000,000	'	'	9,000,000
Office and delay rental expense	6,700,000	12,100,000	7,700,000	49,100,000
Drilling Rig and Related Contracts	'	'	'	'
Contractual obligation and commitments	'	'	'	'
2014	349,000,000	'	'	349,000,000
2015	521,000,000	'	'	521,000,000
2016	295,000,000	'	'	295,000,000
2017	207,000,000	'	'	207,000,000
Operating Leases	'	'	'	'
Contractual obligation and commitments	'	'	'	'
2014	13,000,000	'	'	13,000,000
2015	11,000,000	'	'	11,000,000
2016	8,000,000	'	'	8,000,000
2017	5,000,000	'	'	5,000,000
2018	4,000,000	'	'	4,000,000
Thereafter	8,000,000	'	'	8,000,000
Lease Rentals	'	'	'	'
Contractual obligation and commitments	'	'	'	'
2014	6,000,000	'	'	6,000,000
2015	6,000,000	'	'	6,000,000
2016	4,000,000	'	'	4,000,000
2017	3,000,000	'	'	3,000,000
2018	1,000,000	'	'	1,000,000
Thereafter	1,000,000	'	'	1,000,000
Social Payment Obligations	'	'	'	'
Contractual obligation and commitments	'	'	'	'
2014	49,019,000	'	'	49,019,000
2015	50,619,000	'	'	50,619,000
2016	62,854,000	'	'	62,854,000
2017	5,714,000	'	'	5,714,000
2018	$5,714,000	'	'	$5,714,000

Segment_Information_Details

Segment Information (Details) (USD $)

3 Months Ended

12 Months Ended

24 Months Ended

98 Months Ended

In Thousands, unless otherwise specified

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2013

segment

Segment Information

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of geographic operating segments

'

'

'

'

'

'

'

'

2

'

'

'

'

Segment Information

'

'

'

'

'

'

'

'

'

'

'

'

'

Operating costs and expense

$209,204

$145,663

$65,365

$112,452

$64,405

$40,553

$142,155

$37,715

$532,684

$284,828

$137,836

'

$1,472,283

Operating income (loss)

-209,204

-145,663

-65,365

-112,452

-64,405

-40,553

-142,155

-37,715

-532,684

-284,828

-137,836

'

-1,472,283

Other income (expense)

'

'

'

'

'

'

'

'

-56,340

1,829

4,199

'

-44,576

Net income (loss)

-222,119

-160,000

-78,818

-128,087

-66,531

-39,214

-140,723

-36,531

-589,024

-282,999

-133,637

-217,733

-1,516,859

Additions to Property and Equipment, net

'

'

'

'

'

'

'

'

376,519

236,430

399,558

'

'

United States

'

'

'

'

'

'

'

'

'

'

'

'

'

Segment Information

'

'

'

'

'

'

'

'

'

'

'

'

'

Operating costs and expense

'

'

'

'

'

'

'

'

329,832

231,196

80,425

'

'

Operating income (loss)

'

'

'

'

'

'

'

'

-329,832

-231,196

-80,425

'

'

Additions to Property and Equipment, net

'

'

'

'

'

'

'

'

44,124

67,068

-12,324

'

'

West Africa

'

'

'

'

'

'

'

'

'

'

'

'

'

Segment Information

'

'

'

'

'

'

'

'

'

'

'

'

'

Operating costs and expense

'

'

'

'

'

'

'

'

202,852

53,632

57,411

'

'

Operating income (loss)

'

'

'

'

'

'

'

'

-202,852

-53,632

-57,411

'

'

Additions to Property and Equipment, net

'

'

'

'

'

'

'

'

$332,395

$169,362

$411,882

'

'

Related_Party_Transactions_Det

Related Party Transactions (Details) (Software licensing and consulting service agreement, USD $)	0 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Feb. 20, 2013	Dec. 31, 2013
Related party transactions	'	'
Value of agreement	1.5	'
Quorum	'	'
Related party transactions	'	'
Initial term to license, host and support software	'3 years	'
Amount incurred	'	$1.30

Selected_Quarterly_Financial_D2

Selected Quarterly Financial Data-Unaudited (Details) (USD $)	3 Months Ended								12 Months Ended			24 Months Ended	98 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013
Selected Quarterly Financial Data Unaudited	'	'	'	'	'	'	'	'	'	'	'	'	'
Operating costs and expenses	$209,204	$145,663	$65,365	$112,452	$64,405	$40,553	$142,155	$37,715	$532,684	$284,828	$137,836	'	$1,472,283
Operating income (loss)	-209,204	-145,663	-65,365	-112,452	-64,405	-40,553	-142,155	-37,715	-532,684	-284,828	-137,836	'	-1,472,283
Net income (loss)	($222,119)	($160,000)	($78,818)	($128,087)	($66,531)	($39,214)	($140,723)	($36,531)	($589,024)	($282,999)	($133,637)	($217,733)	($1,516,859)
Basic and diluted income (loss) per common share (in dollars per share)	($0.55)	($0.39)	($0.19)	($0.31)	($0.16)	($0.10)	($0.35)	($0.09)	($1.45)	($0.70)	($0.35)	'	'

Supplemental_Information_on_Oi2

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Capitalized Costs Related to Oil and Gas Activities	'	'
Unproved properties	$1,532,717,000	$1,172,877,000
Accumulated valuation allowance	-160,913,000	-78,413,000
Capitalized costs, gross	1,371,804,000	1,094,464,000
Proved properties	92,579,000	'
Net capitalized costs	1,464,383,000	1,094,464,000
Gain (loss) recognized on sale and exchange of leasehold interests transactions	0	0
U.S. Gulf of Mexico	'	'
Capitalized Costs Related to Oil and Gas Activities	'	'
Unproved properties	605,658,000	572,257,000
Accumulated valuation allowance	-160,913,000	-78,413,000
Capitalized costs, gross	444,745,000	493,844,000
Proved properties	92,579,000	'
Net capitalized costs	537,324,000	493,844,000
Proceeds from sale and exchange of leasehold interests transactions	10,700,000	800,000
West Africa	'	'
Capitalized Costs Related to Oil and Gas Activities	'	'
Unproved properties	927,059,000	600,620,000
Capitalized costs, gross	927,059,000	600,620,000
Net capitalized costs	$927,059,000	$600,620,000

Supplemental_Information_on_Oi3

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Details 2) (USD $)	12 Months Ended			98 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Property acquisition	'	'	'	'
Unproved	$37,584	$19,961	$337,126	'
Exploration	'	'	'	'
Capitalized	628,685	346,604	108,063	'
Expensed	74,213	61,583	32,239	464,385
Development	54,133	'	'	'
Total Costs Incurred	794,615	428,148	477,428	'
U.S. Gulf of Mexico	'	'	'	'
Property acquisition	'	'	'	'
Unproved	37,584	19,961	'	'
Exploration	'	'	'	'
Capitalized	158,806	178,295	11,214	'
Expensed	48,688	32,874	10,707	'
Development	54,133	'	'	'
Total Costs Incurred	299,211	231,130	21,921	'
West Africa	'	'	'	'
Property acquisition	'	'	'	'
Unproved	'	'	337,126	'
Exploration	'	'	'	'
Capitalized	469,879	168,309	96,849	'
Expensed	25,525	28,709	21,532	'
Total Costs Incurred	$495,404	$197,018	$455,507	'

Supplemental_Information_on_Oi4

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Details 3)	12 Months Ended
	Dec. 31, 2013
	MMBoe
Proved undeveloped reserves:	'
Discoveries	8.5
End of year	8.5
Period for calculating un-weighted arithmetic average of the first-day-of-the-month prices	'12 months
Natural Gas (in Bcf)	'
Proved undeveloped reserves:	'
Discoveries	3,400
End of year	3,400
Unweighted average resulting price (in dollars per Bbl or Mcf)	3.507
Natural Gas (in Bcf) | Henry Hub	'
Proved undeveloped reserves:	'
Unweighted arithmetic average price (in dollars per Bbl or MMbtu)	3.67
Oil and Condensate (in MBbls)	'
Proved undeveloped reserves:	'
Discoveries	7.9
End of year	7.9
Unweighted average resulting price (in dollars per Bbl or Mcf)	103.9
Oil and Condensate (in MBbls) | Light Louisiana Sweet	'
Proved undeveloped reserves:	'
Unweighted arithmetic average price (in dollars per Bbl or MMbtu)	107.13

Supplemental_Information_on_Oi5

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Details 4) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Future net cash flows relating to proved oil and gas reserves based on the standardized measure	'
Future cash inflows	$830,287
Future production costs	-6,400
Future development costs	-302,278
Future income tax expense	0
Future net cash flows	521,609
10% annual discount for estimated timing of cash flows	-244,976
Standardized measure of discounted future net cash flows	$276,633

Supplemental_Information_on_Oi6

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Details 5) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Information with respect to the company's standardized measure of discounted future net cash flows related to its proved natural gas reserves	'
Discoveries	$276,633
Standardized measure, ending	$276,633