Cobalt International Energy 10-Q 1 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014
Document and Entity Information	'
Entity Registrant Name	'Cobalt International Energy, Inc.
Entity Central Index Key	'0001471261
Document Type	'10-Q
Document Period End Date	31-Mar-14
Amendment Flag	'false
Current Fiscal Year End Date	'--12-31
Entity Current Reporting Status	'Yes
Entity Filer Category	'Large Accelerated Filer
Entity Common Stock, Shares Outstanding	412,478,706
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'Q1

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$151,804	$192,460
Joint interest and other receivables	77,766	124,639
Prepaid expenses and other current assets	28,509	55,857
Inventory	79,255	74,768
Short-term restricted funds	158,495	200,339
Short-term investments	1,099,489	1,319,380
Total current assets	1,595,318	1,967,443
Property, plant, and equipment:	'	'
Oil and gas properties, successful efforts method of accounting, net of accumulated depletion of $-0-	1,609,463	1,464,383
Other property and equipment, net of accumulated depreciation and amortization of $5,501 and $4,394, as of March 31, 2014 and December 31, 2013, respectively	11,076	11,892
Total property, plant, and equipment, net	1,620,539	1,476,275
Long-term restricted funds	103,237	104,496
Long-term investments	100,008	14,661
Deferred income taxes	12,738	17,061
Other assets	52,381	53,737
Total assets	3,484,221	3,633,673
Current liabilities:	'	'
Trade and other accounts payable	15,337	131,428
Accrued liabilities	194,834	143,459
Short-term contractual obligations	49,687	49,019
Deferred income taxes	12,738	17,061
Total current liabilities	272,596	340,967
Long-term debt	1,047,747	1,035,980
Long-term contractual obligations	81,377	124,901
Other long-term liabilities	2,610	2,679
Total long-term liabilities	1,131,734	1,163,560
Stockholders' Equity:	'	'
Common stock, $0.01 par value per share; 2,000,000,000 shares authorized, 407,059,370 and 406,949,839 issued and outstanding as of March 31, 2014 and December 31, 2013, respectively	4,071	4,069
Additional paid-in capital	3,649,594	3,641,936
Accumulated deficit during the development stage	-1,573,774	-1,516,859
Total stockholders' equity	2,079,891	2,129,146
Total liabilities and stockholders' equity	$3,484,221	$3,633,673

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Condensed 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)	$5,501	$4,394
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	407,059,370	406,949,839
Common stock, shares outstanding	407,059,370	406,949,839

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended		101 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Operating costs and expenses:	'	'	'
Seismic and exploration	$8,976	$22,318	$473,361
Dry hole expense and impairment	13,041	68,168	602,824
General and administrative	24,169	21,507	435,658
Depreciation and amortization	1,107	459	7,733
Total operating costs and expenses	47,293	112,452	1,519,576
Operating income (loss)	-47,293	-112,452	-1,519,576
Other income (expense):	'	'	'
Gain on sale of assets	'	1,497	2,993
Interest income	945	1,525	22,032
Interest expense, net	-10,567	-18,657	-79,223
Total other income (expense)	-9,622	-15,635	-54,198
Net income (loss) before income tax	-56,915	-128,087	-1,573,774
Net income (loss)	($56,915)	($128,087)	($1,573,774)
Basic and diluted income (loss) per common share (in dollars per share)	($0.14)	($0.31)	'
Weighted average common shares outstanding (in shares)	407,001,208	406,651,869	'

Condensed_Consolidated_Stateme1

Condensed 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 Nov. 10, 2005	'	'	'	'	'	'	'
Class A limited partners' contributions	$1,256,738	$1,256,738	'	'	'	'	'
Class B & C limited partners' equity compensation	7,718	'	6,984	734	'	'	'
Common stock issued upon corporate reorganization	'	-1,256,738	-6,984	-734	2,743	1,261,713	'
Common stock issued at initial public offering, net of offering costs	807,259	'	'	'	630	806,629	'
Common stock issued at private placement	42,188	'	'	'	32	42,156	'
Common stock issued at the closing of the over-allotment portion of initial public offering, net of offering costs	101,256	'	'	'	80	101,176	'
Common stock issued at public offering, net of costs	967,512	'	'	'	538	966,974	'
Common stock issued for restricted stock and stock options	'	'	'	'	47	-47	'
Equity based compensation	81,743	'	'	'	'	81,743	'
Exercise of stock options	536	'	'	'	'	536	'
Common stock withheld for taxes on equity based compensation	-361	'	'	'	-1	-360	'
Conversion option relating to 2.625% convertible senior notes, net of allocated costs	381,416	'	'	'	'	381,416	'
Net income (loss)	-1,516,859	'	'	'	'	'	-1,516,859
Balance at Dec. 31, 2013	2,129,146	'	'	'	4,069	3,641,936	-1,516,859
Common stock issued for restricted stock and stock options	'	'	'	'	2	-2	'
Equity based compensation	8,257	'	'	'	'	8,257	'
Exercise of stock options	33	'	'	'	'	33	'
Common stock withheld for taxes on equity based compensation	-630	'	'	'	'	-630	'
Net income (loss)	-56,915	'	'	'	'	'	-56,915
Balance at Mar. 31, 2014	$2,079,891	'	'	'	$4,071	$3,649,594	($1,573,774)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Changes in Partners' Capital and Stockholders' Equity (Parenthetical)	Dec. 31, 2013
Condensed Consolidated Statements of Changes in Partners' Capital and Stockholders' Equity	'
Interest rate (as a percent)	2.63%

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended		101 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Cash flows provided from operating activities	'	'	'
Net income (loss)	($56,915)	($128,087)	($1,573,774)
Adjustments to reconcile net income (loss) to net cash used in operating activities:	'	'	'
Depreciation and amortization	1,107	459	7,733
Dry hole expense and impairment of unproved properties	13,041	68,168	602,824
Gain on sale of assets	'	-1,497	-2,993
Equity based compensation	8,257	6,283	97,718
Amortization of premium (accretion of discount) on investments	4,230	4,822	61,840
Amortization of debt discount	12,352	11,305	60,947
Other	'	'	580
Changes in operating assets and liabilities:	'	'	'
Joint interest and other receivables	46,223	-7,373	-81,939
Inventory	-4,487	2,518	-79,825
Prepaid expense and other current assets	27,348	-6,199	-28,508
Deferred charges	5,094	-2,938	-44,722
Trade and other accounts payable	-116,091	-61,252	15,337
Accrued liabilities and other	-25,832	9,207	38,301
Net cash provided by (used in) operating activities	-85,673	-104,584	-926,481
Cash flows from investing activities	'	'	'
Capital expenditures for oil and gas properties	-42,855	-50,855	-970,242
Capital expenditures for other property and equipment	-291	-111	-18,840
Exploratory wells drilling in process	-85,307	-53,667	-1,277,475
Proceeds from sale of oil and gas properties	'	'	342,007
Change in restricted funds	43,659	90,322	-88,807
Proceeds from maturity of investment securities	519,205	346,709	4,485,236
Purchase of investment securities	-388,797	-1,326,757	-5,915,325
Net cash provided by (used in) investing activities	45,614	-994,359	-3,443,446
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 offerings, net of costs	'	'	967,513
Proceeds from debt offering, net of costs	'	-1,190	1,347,760
Proceeds from stock option exercises	33	74	569
Payments for common stock withheld for taxes on equity based compensation	-630	'	-993
Net cash provided by (used in) financing activities	-597	-1,116	4,521,731
Net increase (decrease) in cash and cash equivalents	-40,656	-1,100,059	151,804
Cash and cash equivalents, beginning of period	192,460	1,425,815	'
Cash and cash equivalents, end of period	151,804	325,756	151,804
Non-Cash Disclosures	'	'	'
Changes in accrued capital expenditures	29,959	35,147	29,959
Transfer of investment securities to and from restricted funds	$42,672	$26	$221,476

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Summary of Significant Accounting Policies	'
Summary of Significant Accounting Policies	'
	1. Summary of Significant Accounting Policies
	General
	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.
	Basis of Presentation
	The accompanying unaudited condensed 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 periods presented. Because the Company is a development stage enterprise, it has presented its financial statements in accordance with accounting guidance related to "Development Stage Entities."
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles ("GAAP") for interim financial information and the appropriate rules and regulations of the Securities and Exchange Commission ("SEC"). Accordingly, the condensed consolidated financial statements do not include all of the information and footnote disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for interim periods are not necessarily indicative of the results that may be presented for the entire year. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company's Annual Report on Form 10-K for the year ended December 31, 2013.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets 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 made by the Company include (i) accruals related to expenses, (ii) assumptions used in estimating fair value of equity based awards and the fair value of the liability component of the convertible senior notes and (iii) assumptions used in impairment testing. Although the Company believes these estimates are reasonable, actual results could differ from these estimates.
	Investments
	The Company's policy on accounting for its investments, which consist entirely of debt securities, 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 securities is adjusted for amortization of premiums and accretion of discounts to maturity over the life of the securities. Held-to-maturity securities are stated at amortized cost, which approximates fair market value as of March 31, 2014 and December 31, 2013. Income related to these securities is reported as a component of interest income in the Company's condensed consolidated statement of operations. See Note 5—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 March 31, 2014 and December 31, 2013, 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 7—Property, Plant, and Equipment and Note 9—Long-term Debt.
	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 2.625% convertible senior notes due 2019, during the period, unless their effect is anti-dilutive. For the three months ended March 31, 2014 and 2013, 8,606,462 and 6,848,139 shares of non-vested restricted stock, non-vested restricted stock units, outstanding stock options and the Company's 2.625% convertible senior notes due 2019, respectively, were excluded from the diluted income (loss) per share because they are anti-dilutive.

Cash_and_Cash_Equivalents

Cash and Cash Equivalents	3 Months Ended
	Mar. 31, 2014
Cash and Cash Equivalents	'
Cash and Cash Equivalents	'
	2. Cash and Cash Equivalents
	Cash and cash equivalents consisted of the following:
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Cash at banks	$	34,340	$	82,428
	Money market funds		65,995		75,039
	Held-to-maturity securities(1)		51,469		34,993
		$	151,804	$	192,460
	-1
	These securities mature three months or less from the date of purchase.

Restricted_Funds

Restricted Funds	3 Months Ended
	Mar. 31, 2014
Restricted Funds	'
Restricted Funds	'
	3. Restricted Funds
	Restricted funds consisted of the following:
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Short-term:
	Collateral on letters of credit for Angola(1)	$	158,495	$	200,339
		$	158,495	$	200,339
	Long-term:
	Collateral on letters of credit for Angola	$	103,237	$	104,496
		$	103,237	$	104,496
	-1
	As of March 31, 2014 and December 31, 2013, $261.7 million and $304.8 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 March 31, 2014 and 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 $261.7 million and $304.8 million, respectively. The contractual maturities of these securities are within one year. The $158.5 million classified as short-term restricted funds at March 31, 2014 includes $111.8 million of cash collateral associated with letters of credit issued in support of work program obligations which have been completed for Block 20 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 has been extended to March 1, 2016.

Joint_Interest_and_Other_Recei

Joint Interest and Other Receivables	3 Months Ended
	Mar. 31, 2014
Joint Interest and Other Receivables	'
Joint Interest and Other Receivables	'
	4. 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 are usually settled within 30 days of the invoice date. As of March 31, 2014 and December 31, 2013, the balance in joint interest and other receivables consisted of the following:
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Partners in the U.S. Gulf of Mexico	$	5,693	$	68,664
	Partners in West Africa(1)		60,198		46,897
	Accrued interest on investment securities		6,792		5,632
	Other		5,083		3,446
		$	77,766	$	124,639
	-1
	The amount of $60.2 million as of March 31, 2014 includes $28.7 million related to the Company's partners on Block 20 offshore Angola and $31.5 million related to the outstanding balance due from the Company's partners on Blocks 9 and 21 offshore Angola.

Investments

Investments	3 Months Ended
	Mar. 31, 2014
Investments	'
Investments	'
	5. Investments
	The Company's investments in held-to-maturity securities which are recorded at amortized cost and approximate fair market value, were as follows as of March 31, 2014 and December 31, 2013:
		March 31,		December 31,
		2014		2013
		($ in thousands)
	U.S. Treasury bills	$	87,850	$	304,834
	U.S. Treasury notes		216,552		—
	Corporate securities		779,887		856,002
	Commercial paper		353,409		408,033
	Certificates of deposit		75,000		105,000
	Total	$	1,512,698	$	1,673,869
	The Company's condensed consolidated balance sheet included the following held-to-maturity securities:
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Cash and cash equivalents	$	51,469	$	34,993
	Short-term investments		1,099,489		1,319,380
	Short-term restricted funds		158,495		200,339
	Long-term restricted funds		103,237		104,496
	Long-term investments		100,008		14,661
		$	1,512,698	$	1,673,869
	The contractual maturities of these held-to-maturity securities as of March 31, 2014 and December 31, 2013 were as follows:
		March 31, 2014				December 31, 2013
		Carrying		Estimated		Carrying		Estimated
		Value		Fair Value		Value		Fair Value
		($ in thousands)
	Within 1 year	$	1,412,690	$	1,412,690	$	1,659,208	$	1,659,208
	After 1 year		100,008		100,008		14,661		14,661
		$	1,512,698	$	1,512,698	$	1,673,869	$	1,673,869

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2014
Fair Value Measurements	'
Fair Value Measurements	'
	6. 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, commercial paper, corporate 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.
	The following tables summarize the Company's significant financial instruments as categorized by the fair value measurement hierarchy:
		Level 1				Level 2
										Balance
										as of
										March 31,
		Carrying		Fair		Carrying		Fair		2014
		Value		Value(1)		Value		Value(1)
		($ in thousands)
	Cash and cash equivalents:
	Cash	$	34,340	$	34,340	$	—	$	—	$	34,340
	Money market funds		65,995		65,995		—		—		65,995
	U.S. Treasury bills		—		—		42,671		42,671		42,671
	Commercial paper		—		—		8,798		8,798		8,798
	Subtotal		100,335		100,335		51,469		51,469		151,804
	Short-term restricted funds:
	U.S. Treasury notes		—		—		45,179		45,179		45,179
	U.S. Treasury bills		—		—		113,316		113,316		113,316
	Subtotal		—		—		158,495		158,495		158,495
	Short-term investments:
	Corporate bonds		—		—		679,879		679,879		679,879
	Commercial paper		—		—		344,610		344,610		344,610
	Certificates of deposits		—		—		75,000		75,000		75,000
	Subtotal		—		—		1,099,489		1,099,489		1,099,489
	Long-term restricted funds:
	U.S. Treasury notes		—		—		103,237		103,237		103,237
	Subtotal		—		—		103,237		103,237		103,237
	Long-term investments:
	Corporate bonds		—		—		100,008		100,008		100,008
	Subtotal		—		—		100,008		100,008		100,008
	Total	$	100,335	$	100,335	$	1,512,698	$	1,512,698	$	1,613,033
		Level 1				Level 2
										Balance
										as of
										December 31,
		Carrying		Fair		Carrying		Fair		2013
		Value		Value(1)		Value		Value(1)
		($ 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
-1
As of March 31, 2014 and December 31, 2013, the Company did not record any OTTI on these assets.

Property_Plant_and_Equipment

Property, Plant, and Equipment	3 Months Ended
	Mar. 31, 2014
Property, Plant, and Equipment	'
Property, Plant, and Equipment	'
	7. Property, Plant, and Equipment
	Property, plant, and equipment is stated at cost less accumulated depreciation/amortization and consisted of the following:
		Estimated		March 31,			December 31,
		Useful Life		2014			2013
		(Years)
				($ in thousands)
	Oil and Gas Properties:
	Proved properties:
	Well and development costs			$	108,227		$	92,579
	Total proved properties				108,227			92,579
	Unproved properties:
	Oil and gas leasehold				754,267			754,894
	Less: accumulated valuation allowance				(169,948	)		(160,913	)
					584,319			593,981
	Exploration wells in process				916,917			777,823
	Total unproved properties				1,501,236			1,371,804
	Total oil and gas properties, net				1,609,463			1,464,383
	Other Property and Equipment:
	Computer equipment and software	3			5,406			5,115
	Office equipment and furniture	3 - 5			2,132			2,132
	Vehicles	3			265			265
	Leasehold improvements	3 - 10			2,456			2,456
	Running tools and equipment	3			6,318			6,318
					16,577			16,286
	Less: accumulated depreciation and amortization(1)				(5,501	)		(4,394	)
	Total other property and equipment, net				11,076			11,892
	Property, plant, and equipment, net			$	1,620,539		$	1,476,275
	The Company recorded $1.1 million, $0.5 million and $7.7 million of depreciation and amortization expense for the three months ended March 31, 2014 and 2013, and for the period November 10, 2005 (inception) through March 31, 2014, 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 March 31, 2014, 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 $76.6 million for costs associated with field development. 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 $61.0 million for costs associated with field development.
	Unproved Oil and Gas Properties
	As of March 31, 2014 and December 31, 2013, the Company has the following unproved property acquisition costs, net of valuation allowance on the consolidated balance sheets:
		March 31,			December 31,
		2014			2013
		($ in thousands)
	U.S. Gulf of Mexico:
	Individual oil and gas leaseholds with carrying value greater than $1 million	$	327,869		$	328,128
	Individual oil and gas leaseholds with carrying value less than $1 million		68,527			68,895
			396,396			397,023
	Accumulated valuation allowance & impairment		(169,948	)		(160,913	)
			226,448			236,110
	West Africa:
	Blocks 9, 20 and 21 offshore Angola		355,876			355,876
	Diaba Block offshore Gabon		1,995			1,995
			357,871			357,871
	Total oil and gas leasehold	$	584,319		$	593,981
	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):
		March 31,			December 31,
		2014			2013
		($ in thousands)
	Beginning of period	$	777,823		$	451,024
	Additions to capitalized exploration
	U.S. Gulf of Mexico:
	Exploration well costs		17,524			154,877
	Capitalized interest		1,251			3,928
	West Africa:
	Exploration well costs		115,465			457,608
	Capitalized interest		8,234			12,271
	Reclassifications to wells, facilities, and equipment based on determination of proved reserves		—			(38,446	)
	Amounts charged to expense(1)		(3,380	)		(263,439	)
	End of period	$	916,917		$	777,823
-1
The amounts of $3.4 million and $263.4 million for the three months ended March 31, 2014 and for the year ended December 31, 2013, respectively, represent impairment charges on exploration wells drilled offshore U.S. Gulf of Mexico, offshore Angola and offshore Gabon which did not encounter commercial hydrocarbons.
	March 31,			December 31,
	2014			2013
	($ in thousands)
Cumulative costs:
U.S. Gulf of Mexico
Exploration well costs	$	219,011		$	204,707
Capitalized interest		5,179			3,928
West Africa
Exploration well costs		672,222			556,917
Capitalized interest		20,505			12,271
	$	916,917		$	777,823
Well costs capitalized for a period greater than one year after completion of drilling (included in table above)	$	404,920		$	399,775
As of March 31, 2014, capitalized exploration well costs that have been suspended longer than one year are associated with the Company's Shenandoah, North Platte and Cameia discoveries. Capitalized exploration well costs associated with our Orca, Lontra, Bicuar, Mavinga and Diaman discoveries have been suspended for less than one year. 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 in 2013.

Other_Assets

Other Assets	3 Months Ended
	Mar. 31, 2014
Other Assets	'
Other Assets	'
	8. Other Assets
	As of March 31, 2014 and December 31, 2013, the balance in other assets consisted of the following:
		March 31,		December 31,
		2014		2013
		(in thousands)
	Debt issue cost(1)	$	20,399	$	20,983
	Long-term portion of prepaid shorebase leases		2,492		3,241
	Rig mobilization costs(2)		9,086		11,153
	Long-term accounts receivable(3)		19,967		17,923
	Other		437		437
		$	52,381	$	53,737
	-1
	As of March 31, 2014 and December 31, 2013, the $20.4 million and $21.0 million, respectively, in debt issue cost relate to the issuance of the Company's 2.625% convertible senior notes due 2019, as described in Note 9, and which are amortized over the life of the notes using the effective interest method.
	-2
	As of March 31, 2014 and December 31, 2013, the $9.1 million and $11.2 million, respectively, relate 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 March 31, 2014 and December 31, 2013, these expenditures totaled approximately $20.0 million and $17.9 million, respectively, which were 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	3 Months Ended
	Mar. 31, 2014
Long-term Debt	'
Long-term Debt	'
	9. 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 three months ended March 31, 2014, the Company recorded $12.1 million in accrued 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 $9.1 million to the equity component of the Notes. The debt discount and the liability component of the debt issue costs are amortized over the term of the Notes. The effective interest rate used to amortize the debt discount and the liability component of the debt issue costs was approximately 8.40% based on the Company's estimated non-convertible borrowing rate as of the date the Notes were issued. Since the Company incurred losses for all periods, the impact of the conversion option would be anti-dilutive to the earnings per share and therefore was not included in the calculation.
	The carrying amounts of the liability components of the Notes were as follows:
		March 31, 2014								December 31, 2013
		Principal			Unamortized			Carrying		Principal		Unamortized			Carrying
		Amount			discount(1)			Amount		Amount		discount			Amount
		($ in thousands)
	Carrying amount of liability component
	2.625% convertible senior notes	$	1,380,000		$	(332,253	)	$	1,047,747	$	1,380,000	$	(344,020	)	$	1,035,980
	-1
	Unamortized discount will be amortized over the remaining life of the Notes which is 5.75 years.
	The carrying amounts of the equity components of the Notes were as follows:
		March 31,			December 31,
		2014			2013
		($ 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 $1,172.2 million and $1,227.1 million as of March 31, 2014 and December 31, 2013, respectively, and was calculated based on the fair value of similar non-convertible debt instruments since an observable quoted price of the Notes or a similar asset or liability is not readily available.
	For the three months ended March 31, 2014 and 2013, the interest expense, net of capitalized amount, relating to the Notes was $10.6 million and $18.7 million, respectively. For the period from November 10, 2005 (inception) to March 31, 2014, the interest expense, net of capitalized amount, was $79.2 million.

Contractual_Obligations

Contractual Obligations	3 Months Ended
	Mar. 31, 2014
Contractual Obligations	'
Contractual Obligations	'
	10. Contractual Obligations
	The short-term and long-term contractual obligations consist of the following:
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Short-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	—	$	150
	Social obligation payments for Block 21, offshore Angola		1,118		300
	Social obligation and bonus payments for Block 20, offshore Angola(1)		48,569		48,569
		$	49,687	$	49,019
	Long-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	—	$	669
	Social obligation payments for Block 21, offshore Angola		1,381		1,381
	Social obligation and bonus payments for Block 20, offshore Angola(1)		79,996		122,851
		$	81,377	$	124,901
	-1
	The total amount of social obligation payments for Block 20 has been capitalized.

Seismic_and_Exploration_Expens

Seismic and Exploration Expenses	3 Months Ended
	Mar. 31, 2014
Seismic and Exploration Expenses	'
Seismic and Exploration Expenses	'
	11. Seismic and Exploration Expenses
	Seismic and exploration expenses consisted of the following:
		Three Months
		Ended March 31,				For the Period
						November 10, 2005
						(Inception) through
		2014		2013		March 31, 2014
		($ in Thousands)
	Seismic costs	$	3,349	$	18,109	$	409,118
	Seismic cost recovery(1)		—		—		(25,126	)
	Leasehold delay rentals		1,291		1,387		40,853
	Force Majeure expense(2)		—		—		13,549
	Drilling rig expense		4,336		2,822		34,967
		$	8,976	$	22,318	$	473,361
	-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 exploratory expenses.

Equity_Based_Compensation

Equity Based Compensation	3 Months Ended
	Mar. 31, 2014
Equity Based Compensation	'
Equity Based Compensation	'
	12. 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, 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. As of March 31, 2014, the final tranche of the restricted stock units relating to the performance-based awards were fully vested.
	During the three months ended March 31, 2014, the Company granted a total of 1,108,367 shares of restricted stock and 812,055 stock options to employees. During the three months ended March 31, 2014, the Company also granted 6,539 shares of common stock as retainer awards to non-employee directors who elected to be compensated by stock in lieu of cash payments.
	For the three months ended March 31, 2014 and 2013, total equity based compensation recognized, net of forfeitures, was $8.3 million and $6.3 million, respectively. For the period November 5, 2005 (inception) through March 31, 2014, total equity based compensation recognized, net of forfeitures, was $97.7 million.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2014
Segment Information	'
Segment Information	'
	13. Segment Information
	The Company currently has two geographic operating segments for its exploratory 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 the three months ended March 31, 2014 and 2013:
		U.S. Gulf of			West Africa			Total
		Mexico
		($ in thousands)
	Three months ended March 31, 2014
	Operating costs and expense	$	31,027		$	16,266		$	47,293
	Operating income (loss)		(31,027	)		(16,266	)		(47,293	)
	Other income (expense)								(9,622	)
	Net income (loss)							$	(56,915	)
	Additions to Property and Equipment, net(1)	$	21,376		$	122,888		$	144,264
	Three months ended March 31, 2013
	Operating costs and expense	$	23,105		$	89,347		$	112,452
	Operating income (loss)		(23,105	)		(89,347	)		(112,452	)
	Other income (expense)								(15,635	)
	Net income (loss)							$	(128,087	)
	Additions to Property and Equipment, net(1)	$	54,859		$	(24,902	)	$	29,957
	-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	3 Months Ended
	Mar. 31, 2014
Contingencies	'
Contingencies	'
	14. 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.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Summary of Significant Accounting Policies	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited condensed 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 periods presented. Because the Company is a development stage enterprise, it has presented its financial statements in accordance with accounting guidance related to "Development Stage Entities."
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles ("GAAP") for interim financial information and the appropriate rules and regulations of the Securities and Exchange Commission ("SEC"). Accordingly, the condensed consolidated financial statements do not include all of the information and footnote disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for interim periods are not necessarily indicative of the results that may be presented for the entire year. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company's Annual Report on Form 10-K for the year ended December 31, 2013.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets 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 made by the Company include (i) accruals related to expenses, (ii) assumptions used in estimating fair value of equity based awards and the fair value of the liability component of the convertible senior notes and (iii) assumptions used in impairment testing. Although the Company believes these estimates are reasonable, actual results could differ from these estimates.
Investments	'
	Investments
	The Company's policy on accounting for its investments, which consist entirely of debt securities, 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 securities is adjusted for amortization of premiums and accretion of discounts to maturity over the life of the securities. Held-to-maturity securities are stated at amortized cost, which approximates fair market value as of March 31, 2014 and December 31, 2013. Income related to these securities is reported as a component of interest income in the Company's condensed consolidated statement of operations. See Note 5—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 March 31, 2014 and December 31, 2013, 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 7—Property, Plant, and Equipment and Note 9—Long-term Debt.
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 2.625% convertible senior notes due 2019, during the period, unless their effect is anti-dilutive. For the three months ended March 31, 2014 and 2013, 8,606,462 and 6,848,139 shares of non-vested restricted stock, non-vested restricted stock units, outstanding stock options and the Company's 2.625% convertible senior notes due 2019, respectively, were excluded from the diluted income (loss) per share because they are anti-dilutive.

Cash_and_Cash_Equivalents_Tabl

Cash and Cash Equivalents (Tables)	3 Months Ended
	Mar. 31, 2014
Cash and Cash Equivalents	'
Cash and cash equivalents	'
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Cash at banks	$	34,340	$	82,428
	Money market funds		65,995		75,039
	Held-to-maturity securities(1)		51,469		34,993
		$	151,804	$	192,460
	-1
	These securities mature three months or less from the date of purchase.

Restricted_Funds_Tables

Restricted Funds (Tables)	3 Months Ended
	Mar. 31, 2014
Restricted Funds	'
Schedule of restricted funds	'
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Short-term:
	Collateral on letters of credit for Angola(1)	$	158,495	$	200,339
		$	158,495	$	200,339
	Long-term:
	Collateral on letters of credit for Angola	$	103,237	$	104,496
		$	103,237	$	104,496
	-1
	As of March 31, 2014 and December 31, 2013, $261.7 million and $304.8 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 March 31, 2014 and 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 $261.7 million and $304.8 million, respectively. The contractual maturities of these securities are within one year. The $158.5 million classified as short-term restricted funds at March 31, 2014 includes $111.8 million of cash collateral associated with letters of credit issued in support of work program obligations which have been completed for Block 20 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 has been extended to March 1, 2016.

Joint_Interest_and_Other_Recei1

Joint Interest and Other Receivables (Tables)	3 Months Ended
	Mar. 31, 2014
Joint Interest and Other Receivables	'
Schedule of joint interest and other receivables	'
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Partners in the U.S. Gulf of Mexico	$	5,693	$	68,664
	Partners in West Africa(1)		60,198		46,897
	Accrued interest on investment securities		6,792		5,632
	Other		5,083		3,446
		$	77,766	$	124,639
	-1
	The amount of $60.2 million as of March 31, 2014 includes $28.7 million related to the Company's partners on Block 20 offshore Angola and $31.5 million related to the outstanding balance due from the Company's partners on Blocks 9 and 21 offshore Angola.

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2014
Investments	'
Schedule of fair value of held-to-maturity securities recorded at amortized cost	'
		March 31,		December 31,
		2014		2013
		($ in thousands)
	U.S. Treasury bills	$	87,850	$	304,834
	U.S. Treasury notes		216,552		—
	Corporate securities		779,887		856,002
	Commercial paper		353,409		408,033
	Certificates of deposit		75,000		105,000
	Total	$	1,512,698	$	1,673,869
Schedule of held-to-maturity securities included in the company's condensed consolidated balance sheet	'
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Cash and cash equivalents	$	51,469	$	34,993
	Short-term investments		1,099,489		1,319,380
	Short-term restricted funds		158,495		200,339
	Long-term restricted funds		103,237		104,496
	Long-term investments		100,008		14,661
		$	1,512,698	$	1,673,869
Schedule of contractual maturities of held-to-maturity securities	'
		March 31, 2014				December 31, 2013
		Carrying		Estimated		Carrying		Estimated
		Value		Fair Value		Value		Fair Value
		($ in thousands)
	Within 1 year	$	1,412,690	$	1,412,690	$	1,659,208	$	1,659,208
	After 1 year		100,008		100,008		14,661		14,661
		$	1,512,698	$	1,512,698	$	1,673,869	$	1,673,869

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value Measurements	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'
		Level 1				Level 2
										Balance
										as of
										March 31,
		Carrying		Fair		Carrying		Fair		2014
		Value		Value(1)		Value		Value(1)
		($ in thousands)
	Cash and cash equivalents:
	Cash	$	34,340	$	34,340	$	—	$	—	$	34,340
	Money market funds		65,995		65,995		—		—		65,995
	U.S. Treasury bills		—		—		42,671		42,671		42,671
	Commercial paper		—		—		8,798		8,798		8,798
	Subtotal		100,335		100,335		51,469		51,469		151,804
	Short-term restricted funds:
	U.S. Treasury notes		—		—		45,179		45,179		45,179
	U.S. Treasury bills		—		—		113,316		113,316		113,316
	Subtotal		—		—		158,495		158,495		158,495
	Short-term investments:
	Corporate bonds		—		—		679,879		679,879		679,879
	Commercial paper		—		—		344,610		344,610		344,610
	Certificates of deposits		—		—		75,000		75,000		75,000
	Subtotal		—		—		1,099,489		1,099,489		1,099,489
	Long-term restricted funds:
	U.S. Treasury notes		—		—		103,237		103,237		103,237
	Subtotal		—		—		103,237		103,237		103,237
	Long-term investments:
	Corporate bonds		—		—		100,008		100,008		100,008
	Subtotal		—		—		100,008		100,008		100,008
	Total	$	100,335	$	100,335	$	1,512,698	$	1,512,698	$	1,613,033
		Level 1				Level 2
										Balance
										as of
										December 31,
		Carrying		Fair		Carrying		Fair		2013
		Value		Value(1)		Value		Value(1)
		($ 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
	-1
	As of March 31, 2014 and December 31, 2013, the Company did not record any OTTI on these assets.

Property_Plant_and_Equipment_T

Property, Plant, and Equipment (Tables)	3 Months Ended
	Mar. 31, 2014
Property, Plant, and Equipment	'
Schedule of Property, Plant, and Equipment	'
		Estimated		March 31,			December 31,
		Useful Life		2014			2013
		(Years)
				($ in thousands)
	Oil and Gas Properties:
	Proved properties:
	Well and development costs			$	108,227		$	92,579
	Total proved properties				108,227			92,579
	Unproved properties:
	Oil and gas leasehold				754,267			754,894
	Less: accumulated valuation allowance				(169,948	)		(160,913	)
					584,319			593,981
	Exploration wells in process				916,917			777,823
	Total unproved properties				1,501,236			1,371,804
	Total oil and gas properties, net				1,609,463			1,464,383
	Other Property and Equipment:
	Computer equipment and software	3			5,406			5,115
	Office equipment and furniture	3 - 5			2,132			2,132
	Vehicles	3			265			265
	Leasehold improvements	3 - 10			2,456			2,456
	Running tools and equipment	3			6,318			6,318
					16,577			16,286
	Less: accumulated depreciation and amortization(1)				(5,501	)		(4,394	)
	Total other property and equipment, net				11,076			11,892
	Property, plant, and equipment, net			$	1,620,539		$	1,476,275
Schedule of unproved property acquisition costs, net of valuation allowance	'
		March 31,			December 31,
		2014			2013
		($ in thousands)
	U.S. Gulf of Mexico:
	Individual oil and gas leaseholds with carrying value greater than $1 million	$	327,869		$	328,128
	Individual oil and gas leaseholds with carrying value less than $1 million		68,527			68,895
			396,396			397,023
	Accumulated valuation allowance & impairment		(169,948	)		(160,913	)
			226,448			236,110
	West Africa:
	Blocks 9, 20 and 21 offshore Angola		355,876			355,876
	Diaba Block offshore Gabon		1,995			1,995
			357,871			357,871
	Total oil and gas leasehold	$	584,319		$	593,981
Schedule of net changes in capitalized exploration well costs	'
		March 31,			December 31,
		2014			2013
		($ in thousands)
	Beginning of period	$	777,823		$	451,024
	Additions to capitalized exploration
	U.S. Gulf of Mexico:
	Exploration well costs		17,524			154,877
	Capitalized interest		1,251			3,928
	West Africa:
	Exploration well costs		115,465			457,608
	Capitalized interest		8,234			12,271
	Reclassifications to wells, facilities, and equipment based on determination of proved reserves		—			(38,446	)
	Amounts charged to expense(1)		(3,380	)		(263,439	)
	End of period	$	916,917		$	777,823
	-1
	The amounts of $3.4 million and $263.4 million for the three months ended March 31, 2014 and for the year ended December 31, 2013, respectively, represent impairment charges on exploration wells drilled offshore U.S. Gulf of Mexico, offshore Angola and offshore Gabon which did not encounter commercial hydrocarbons.
Schedule of cumulative costs of capitalized exploration well costs	'
		March 31,			December 31,
		2014			2013
		($ in thousands)
	Cumulative costs:
	U.S. Gulf of Mexico
	Exploration well costs	$	219,011		$	204,707
	Capitalized interest		5,179			3,928
	West Africa
	Exploration well costs		672,222			556,917
	Capitalized interest		20,505			12,271
		$	916,917		$	777,823
	Well costs capitalized for a period greater than one year after completion of drilling (included in table above)	$	404,920		$	399,775

Other_Assets_Table

Other Assets (Table)	3 Months Ended
	Mar. 31, 2014
Other Assets	'
Schedule of other assets	'
		March 31,		December 31,
		2014		2013
		(in thousands)
	Debt issue cost(1)	$	20,399	$	20,983
	Long-term portion of prepaid shorebase leases		2,492		3,241
	Rig mobilization costs(2)		9,086		11,153
	Long-term accounts receivable(3)		19,967		17,923
	Other		437		437
		$	52,381	$	53,737
	-1
	As of March 31, 2014 and December 31, 2013, the $20.4 million and $21.0 million, respectively, in debt issue cost relate to the issuance of the Company's 2.625% convertible senior notes due 2019, as described in Note 9, and which are amortized over the life of the notes using the effective interest method.
	-2
	As of March 31, 2014 and December 31, 2013, the $9.1 million and $11.2 million, respectively, relate 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 March 31, 2014 and December 31, 2013, these expenditures totaled approximately $20.0 million and $17.9 million, respectively, which were 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)	3 Months Ended
	Mar. 31, 2014
Long-term Debt	'
Schedule of the carrying amounts of the liability components of the Notes	'
		March 31, 2014								December 31, 2013
		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	$	1,380,000		$	(332,253	)	$	1,047,747	$	1,380,000	$	(344,020	)	$	1,035,980
	-1
	Unamortized discount will be amortized over the remaining life of the Notes which is 5.75 years.
Schedule of carrying amounts of the equity components of the Notes	'
		March 31,			December 31,
		2014			2013
		($ 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

Contractual_Obligations_Tables

Contractual Obligations (Tables)	3 Months Ended
	Mar. 31, 2014
Contractual Obligations	'
Summary of components of short-term and long-term contractual obligations	'
		March 31,		December 31,
		2014		2013
		($ in thousands)
	Short-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	—	$	150
	Social obligation payments for Block 21, offshore Angola		1,118		300
	Social obligation and bonus payments for Block 20, offshore Angola(1)		48,569		48,569
		$	49,687	$	49,019
	Long-term Contractual Obligations:
	Social obligation payments for Block 9, offshore Angola	$	—	$	669
	Social obligation payments for Block 21, offshore Angola		1,381		1,381
	Social obligation and bonus payments for Block 20, offshore Angola(1)		79,996		122,851
		$	81,377	$	124,901
	-1
	The total amount of social obligation payments for Block 20 has been capitalized.

Seismic_and_Exploration_Expens1

Seismic and Exploration Expenses (Tables)	3 Months Ended
	Mar. 31, 2014
Seismic and Exploration Expenses	'
Schedule of seismic and exploration expenses	'
		Three Months
		Ended March 31,				For the Period
						November 10, 2005
						(Inception) through
		2014		2013		March 31, 2014
		($ in Thousands)
	Seismic costs	$	3,349	$	18,109	$	409,118
	Seismic cost recovery(1)		—		—		(25,126	)
	Leasehold delay rentals		1,291		1,387		40,853
	Force Majeure expense(2)		—		—		13,549
	Drilling rig expense		4,336		2,822		34,967
		$	8,976	$	22,318	$	473,361
	-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 exploratory expenses.

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Information	'
Schedule of segment information by geographic operating segment	'
		U.S. Gulf of			West Africa			Total
		Mexico
		($ in thousands)
	Three months ended March 31, 2014
	Operating costs and expense	$	31,027		$	16,266		$	47,293
	Operating income (loss)		(31,027	)		(16,266	)		(47,293	)
	Other income (expense)								(9,622	)
	Net income (loss)							$	(56,915	)
	Additions to Property and Equipment, net(1)	$	21,376		$	122,888		$	144,264
	Three months ended March 31, 2013
	Operating costs and expense	$	23,105		$	89,347		$	112,452
	Operating income (loss)		(23,105	)		(89,347	)		(112,452	)
	Other income (expense)								(15,635	)
	Net income (loss)							$	(128,087	)
	Additions to Property and Equipment, net(1)	$	54,859		$	(24,902	)	$	29,957
	-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.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 17, 2012
				2.625% convertible senior notes due 2019	2.625% convertible senior notes due 2019	2.625% convertible senior notes due 2019	2.625% convertible senior notes due 2019
Investments	'	'	'	'	'	'	'
OTTI in debt securities	$0	'	$0	'	'	'	'
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	8,606,462	6,848,139	'	'	'	'	'
Earnings (Loss) Per Share	'	'	'	'	'	'	'
Interest rate (as a percent)	'	'	2.63%	2.63%	2.63%	2.63%	2.63%

Cash_and_Cash_Equivalents_Deta

Cash and Cash Equivalents (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Cash and Cash Equivalents	'	'	'	'
Cash at banks	$34,340	$82,428	'	'
Money market funds	65,995	75,039	'	'
Held-to-maturity securities	51,469	34,993	'	'
Total	$151,804	$192,460	$325,756	$1,425,815

Restricted_Funds_Details

Restricted Funds (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Restricted Funds	'	'
Short-term restricted funds	$158,495,000	$200,339,000
Long-term restricted funds	103,237,000	104,496,000
Block 9, offshore Angola	'	'
Restricted Funds	'	'
Work program obligations secured	45,300,000	'
Collateral on letters of credit for Angola	'	'
Restricted Funds	'	'
Short-term restricted funds	158,495,000	200,339,000
Long-term restricted funds	103,237,000	104,496,000
Collateral held	261,700,000	304,800,000
Maturity period of investments	'1 year	'
Collateral on letters of credit for Angola | U.S. Treasury bills	'	'
Restricted Funds	'	'
Net carrying value of investments invested through the funds	261,700,000	304,800,000
Cash collateral associated with work program obligations which have been completed	'	'
Restricted Funds	'	'
Short-term restricted funds	111,800,000	'
Cash collateral associated with work program obligations which have not been completed	'	'
Restricted Funds	'	'
Short-term restricted funds	$46,700,000	'

Joint_Interest_and_Other_Recei2

Joint Interest and Other Receivables (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Joint Interest and Other Receivables	'	'
Settlement period for bills under operating agreements	'30 days	'
Joint Interest Receivables	'	'
Accrued interest on investment securities	$6,792,000	$5,632,000
Other	5,083,000	3,446,000
Total	77,766,000	124,639,000
Partners in the U.S. Gulf of Mexico	'	'
Joint Interest Receivables	'	'
Receivable attributable to joint interest partners	5,693,000	68,664,000
Partners in West Africa	'	'
Joint Interest Receivables	'	'
Receivable attributable to joint interest partners	60,198,000	46,897,000
Partners in West Africa | Block 20, offshore Angola	'	'
Joint Interest Receivables	'	'
Receivable attributable to joint interest partners	28,700,000	'
Partners in West Africa | Blocks 9 and 21 offshore Angola	'	'
Joint Interest Receivables	'	'
Joint interest and other receivables which became past due	$31,500,000	'

Investments_Details

Investments (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Investments	'	'
Fair market value	$1,512,698	$1,673,869
Held-to-maturities, Carrying value	'	'
Within 1 year	1,412,690	1,659,208
After 1 year	100,008	14,661
Total	1,512,698	1,673,869
Held-to-maturity securities, Estimated fair value	'	'
Within 1 year	1,412,690	1,659,208
After 1 year	100,008	14,661
Total	1,512,698	1,673,869
Cash and cash equivalents	'	'
Investments	'	'
Fair market value	51,469	34,993
Held-to-maturity securities, Estimated fair value	'	'
Total	51,469	34,993
Short-term investments	'	'
Investments	'	'
Fair market value	1,099,489	1,319,380
Held-to-maturity securities, Estimated fair value	'	'
Total	1,099,489	1,319,380
Short-term restricted funds	'	'
Investments	'	'
Fair market value	158,495	200,339
Held-to-maturity securities, Estimated fair value	'	'
Total	158,495	200,339
Long-term restricted funds	'	'
Investments	'	'
Fair market value	103,237	104,496
Held-to-maturity securities, Estimated fair value	'	'
Total	103,237	104,496
Long-term investments	'	'
Investments	'	'
Fair market value	100,008	14,661
Held-to-maturity securities, Estimated fair value	'	'
Total	100,008	14,661
U.S. Treasury bills	'	'
Investments	'	'
Fair market value	87,850	304,834
Held-to-maturity securities, Estimated fair value	'	'
Total	87,850	304,834
U.S. Treasury notes	'	'
Investments	'	'
Fair market value	216,552	'
Held-to-maturity securities, Estimated fair value	'	'
Total	216,552	'
Corporate securities	'	'
Investments	'	'
Fair market value	779,887	856,002
Held-to-maturity securities, Estimated fair value	'	'
Total	779,887	856,002
Commercial paper	'	'
Investments	'	'
Fair market value	353,409	408,033
Held-to-maturity securities, Estimated fair value	'	'
Total	353,409	408,033
Certificates of deposit	'	'
Investments	'	'
Fair market value	75,000	105,000
Held-to-maturity securities, Estimated fair value	'	'
Total	$75,000	$105,000

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	$151,804	$192,460	$325,756	$1,425,815
Short-term restricted funds	158,495	200,339	'	'
Short-term investments	1,099,489	1,319,380	'	'
Long-term restricted funds	103,237	104,496	'	'
Long-term investments	100,008	14,661	'	'
Total	1,613,033	1,831,336	'	'
Cash | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	34,340	82,428	'	'
Money market funds | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	65,995	75,039	'	'
U.S. Treasury bills | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	42,671	'	'	'
Short-term restricted funds	113,316	'	'	'
Commercial paper | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	8,798	9,993	'	'
Short-term investments	344,610	391,073	'	'
Long-term investments	'	6,967	'	'
U.S. Treasury notes | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term restricted funds	45,179	200,339	'	'
Long-term restricted funds	103,237	104,496	'	'
Corporate bonds | Recurring basis	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term investments	679,879	848,307	'	'
Long-term investments	100,008	7,694	'	'
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	75,000	80,000	'	'
Level 1 | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	100,335	157,467	'	'
Total	100,335	157,467	'	'
Level 1 | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	100,335	157,467	'	'
Total	100,335	157,467	'	'
Level 1 | Cash | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	34,340	82,428	'	'
Level 1 | Cash | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	34,340	82,428	'	'
Level 1 | Money market funds | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	65,995	75,039	'	'
Level 1 | Money market funds | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	65,995	75,039	'	'
Level 2 | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	51,469	34,993	'	'
Short-term restricted funds	158,495	200,339	'	'
Short-term investments	1,099,489	1,319,380	'	'
Long-term restricted funds	103,237	104,496	'	'
Long-term investments	100,008	14,661	'	'
Total	1,512,698	1,673,869	'	'
Level 2 | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	51,469	34,993	'	'
Short-term restricted funds	158,495	200,339	'	'
Short-term investments	1,099,489	1,319,380	'	'
Long-term restricted funds	103,237	104,496	'	'
Long-term investments	100,008	14,661	'	'
Total	1,512,698	1,673,869	'	'
Level 2 | U.S. Treasury bills | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	42,671	'	'	'
Short-term restricted funds	113,316	'	'	'
Level 2 | U.S. Treasury bills | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	42,671	'	'	'
Short-term restricted funds	113,316	'	'	'
Level 2 | Commercial paper | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Cash and cash equivalents	8,798	9,993	'	'
Short-term investments	344,610	391,073	'	'
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	8,798	9,993	'	'
Short-term investments	344,610	391,073	'	'
Long-term investments	'	6,967	'	'
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	45,179	200,339	'	'
Long-term restricted funds	103,237	104,496	'	'
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	45,179	200,339	'	'
Long-term restricted funds	103,237	104,496	'	'
Level 2 | Corporate bonds | Recurring basis | Carrying Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term investments	679,879	848,307	'	'
Long-term investments	100,008	7,694	'	'
Level 2 | Corporate bonds | Recurring basis | Fair Value	'	'	'	'
Significant financial instruments as categorized by the fair value measurement hierarchy	'	'	'	'
Short-term investments	679,879	848,307	'	'
Long-term investments	100,008	7,694	'	'
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	75,000	80,000	'	'
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	$75,000	$80,000	'	'

Property_Plant_and_Equipment_D

Property, Plant, and Equipment (Details) (USD $)	3 Months Ended		101 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Dec. 31, 2013
Property, Plant, and Equipment	'	'	'	'
Well and development costs	$108,227,000	'	$108,227,000	$92,579,000
Total proved properties	108,227,000	'	108,227,000	92,579,000
Oil and gas leasehold	754,267,000	'	754,267,000	754,894,000
Less: accumulated valuation allowance	-169,948,000	'	-169,948,000	-160,913,000
Total oil and gas leasehold	584,319,000	'	584,319,000	593,981,000
Total unproved leasehold properties	1,501,236,000	'	1,501,236,000	1,371,804,000
Total oil and gas properties, net	1,609,463,000	'	1,609,463,000	1,464,383,000
Property, plant, and equipment, gross	16,577,000	'	16,577,000	16,286,000
Less: accumulated depreciation and amortization	-5,501,000	'	-5,501,000	-4,394,000
Total other property and equipment	11,076,000	'	11,076,000	11,892,000
Total property, plant, and equipment, net	1,620,539,000	'	1,620,539,000	1,476,275,000
Depreciation and amortization	1,107,000	459,000	7,733,000	'
Unproved property acquisition costs, net of valuation allowance	'	'	'	'
Unproved property	754,267,000	'	754,267,000	754,894,000
Accumulated valuation allowance & impairment	-169,948,000	'	-169,948,000	-160,913,000
Total oil and gas leasehold	584,319,000	'	584,319,000	593,981,000
Exploration well costs	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Well and development costs	31,600,000	'	31,600,000	31,600,000
Well development costs	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Well and development costs	76,600,000	'	76,600,000	61,000,000
Exploration wells in process	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Total unproved leasehold properties	916,917,000	'	916,917,000	777,823,000
Computer equipment and software	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Estimated Useful Life	'3 years	'	'	'
Property, plant, and equipment, gross	5,406,000	'	5,406,000	5,115,000
Office equipment and furniture	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Property, plant, and equipment, gross	2,132,000	'	2,132,000	2,132,000
Office equipment and furniture | Minimum	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Estimated Useful Life	'3 years	'	'	'
Office equipment and furniture | Maximum	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Estimated Useful Life	'5 years	'	'	'
Vehicles	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Estimated Useful Life	'3 years	'	'	'
Property, plant, and equipment, gross	265,000	'	265,000	265,000
Leasehold improvements	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Property, plant, and equipment, gross	2,456,000	'	2,456,000	2,456,000
Leasehold improvements | Minimum	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Estimated Useful Life	'3 years	'	'	'
Leasehold improvements | Maximum	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Estimated Useful Life	'10 years	'	'	'
Running tools and equipment	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Estimated Useful Life	'3 years	'	'	'
Property, plant, and equipment, gross	6,318,000	'	6,318,000	6,318,000
Oil and gas properties, net	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Total oil and gas leasehold	584,319,000	'	584,319,000	593,981,000
Unproved property acquisition costs, net of valuation allowance	'	'	'	'
Total oil and gas leasehold	584,319,000	'	584,319,000	593,981,000
Oil and gas properties, net | U.S. Gulf of Mexico	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Oil and gas leasehold	396,396,000	'	396,396,000	397,023,000
Less: accumulated valuation allowance	-169,948,000	'	-169,948,000	-160,913,000
Unproved property acquisition costs, net of valuation allowance	'	'	'	'
Individual oil and gas leaseholds with carrying value greater than $1 million	327,869,000	'	327,869,000	328,128,000
Individual oil and gas leaseholds with carrying value less than $1 million	68,527,000	'	68,527,000	68,895,000
Unproved property	396,396,000	'	396,396,000	397,023,000
Accumulated valuation allowance & impairment	-169,948,000	'	-169,948,000	-160,913,000
Unproved property, net of valuation allowance	226,448,000	'	226,448,000	236,110,000
Upper limit of individual leasehold	1,000,000	'	1,000,000	1,000,000
Lower limit of individual leasehold	1,000,000	'	1,000,000	1,000,000
Oil and gas properties, net | West Africa	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Oil and gas leasehold	357,871,000	'	357,871,000	357,871,000
Unproved property acquisition costs, net of valuation allowance	'	'	'	'
Unproved property	357,871,000	'	357,871,000	357,871,000
Oil and gas properties, net | Blocks 9, 20 and 21 offshore Angola	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Oil and gas leasehold	355,876,000	'	355,876,000	355,876,000
Unproved property acquisition costs, net of valuation allowance	'	'	'	'
Unproved property	355,876,000	'	355,876,000	355,876,000
Oil and gas properties, net | Diaba Block offshore Gabon	'	'	'	'
Property, Plant, and Equipment	'	'	'	'
Oil and gas leasehold	1,995,000	'	1,995,000	1,995,000
Unproved property acquisition costs, net of valuation allowance	'	'	'	'
Unproved property	$1,995,000	'	$1,995,000	$1,995,000

Property_Plant_and_Equipment_D1

Property, Plant, and Equipment (Details 2) (USD $)	3 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Beginning of period	$777,823	$451,024
Reclassification to wells, facilities, and equipment based on determination of proved reserves	'	-38,446
Amounts charged to expense	-3,380	-263,439
End of period	916,917	777,823
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Cumulative costs	916,917	777,823
Well costs capitalized for a period greater than one year after completion of drilling	404,920	399,775
U.S. Gulf of Mexico | Exploration well costs	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Beginning of period	204,707	'
Additions to capitalized exploration	17,524	154,877
End of period	219,011	204,707
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Cumulative costs	219,011	204,707
U.S. Gulf of Mexico | Capitalized interest	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Beginning of period	3,928	'
Additions to capitalized exploration	1,251	3,928
End of period	5,179	3,928
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Cumulative costs	5,179	3,928
West Africa | Exploration well costs	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Beginning of period	556,917	'
Additions to capitalized exploration	115,465	457,608
End of period	672,222	556,917
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Cumulative costs	672,222	556,917
West Africa | Capitalized interest	'	'
Net changes in capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Beginning of period	12,271	'
Additions to capitalized exploration	8,234	12,271
End of period	20,505	12,271
Cumulative costs of capitalized exploratory well costs (excluding any related leasehold costs)	'	'
Cumulative costs	$20,505	$12,271

Other_Assets_Details

Other Assets (Details) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 17, 2012	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Other Assets	'	'	'	'
Debt issue cost	'	$20,399	$20,983	'
Long-term portion of prepaid shorebase leases	'	2,492	3,241	'
Rig mobilization costs	'	9,086	11,153	'
Long-term accounts receivable	'	19,967	17,923	'
Other	'	437	437	'
Other assets	'	52,381	53,737	'
Interest rate (as a percent)	'	'	2.63%	'
Blocks 9 and 21 offshore Angola	'	'	'	'
Other Assets	'	'	'	'
Long-term accounts receivable	'	20,000	17,900	'
Percentage of paying interest due from related parties	'	3.75%	3.75%	'
Notes	'	'	'	'
Other Assets	'	'	'	'
Debt issue cost	$32,200	$20,400	$21,000	'
Interest rate (as a percent)	2.63%	2.63%	2.63%	2.63%

Longterm_Debt_Details

Long-term Debt (Details) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended	101 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Dec. 17, 2012	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Debt instrument	'	'	'	'	'
Interest rate (as a percent)	'	'	2.63%	'	'
Debt issue cost	'	$20,399,000	$20,983,000	'	'
Carrying amounts of the liability components	'	'	'	'	'
Carrying amount of the liability components	'	1,047,747,000	1,035,980,000	1,047,747,000	'
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%	2.63%
Accrued interest recorded	'	12,100,000	'	12,100,000	'
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	32,200,000	20,400,000	21,000,000	'	'
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	1,380,000,000	'
Unamortized discount	'	-332,253,000	-344,020,000	-332,253,000	'
Carrying amount of the liability components	'	1,047,747,000	1,035,980,000	1,047,747,000	'
Remaining term of debt	'	'5 years 9 months	'	'	'
Carrying amounts of the equity components	'	'	'	'	'
Debt discount relating to value of conversion option	'	390,540,000	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	381,416,000	'
Fair value of the notes excluding conversion feature	'	1,172,200,000	1,227,100,000	1,172,200,000	'
Interest expense, net of capitalized amount	'	$10,600,000	$18,700,000	$79,200,000	'

Contractual_Obligations_Detail

Contractual Obligations (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Contractual obligations	'	'
Short-term Contractual Obligations: Social obligation payments	$49,687	$49,019
Long-term Contractual Obligations: Social obligation payments	81,377	124,901
Block 9, offshore Angola	'	'
Contractual obligations	'	'
Short-term Contractual Obligations: Social obligation payments	'	150
Long-term Contractual Obligations: Social obligation payments	'	669
Block 21, offshore Angola	'	'
Contractual obligations	'	'
Short-term Contractual Obligations: Social obligation payments	1,118	300
Long-term Contractual Obligations: Social obligation payments	1,381	1,381
Block 20, offshore Angola	'	'
Contractual obligations	'	'
Short-term Contractual Obligations: Social obligation payments	48,569	48,569
Long-term Contractual Obligations: Social obligation payments	$79,996	$122,851

Seismic_and_Exploration_Expens2

Seismic and Exploration Expenses (Details) (USD $)	3 Months Ended		101 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Seismic and Exploration Expenses	'	'	'
Seismic costs	$3,349	$18,109	$409,118
Seismic cost recovery	'	'	-25,126
Leasehold delay rentals	1,291	1,387	40,853
Force Majeure expense	'	'	13,549
Drilling rig expense	4,336	2,822	34,967
Total seismic and exploration expenses	$8,976	$22,318	$473,361

Equity_Based_Compensation_Deta

Equity Based Compensation (Details) (USD $)	3 Months Ended		101 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Number of Stock Options	'	'	'
Equity based compensation expense, net of forfeitures recognized	$8,257	$6,283	$97,718
Restricted Stock	'	'	'
Number of shares relating to award	'	'	'
Granted (in shares)	1,108,367	'	'
Retainer awards | Non-employee directors | Common Stock	'	'	'
Number of shares relating to award	'	'	'
Granted (in shares)	6,539	'	'
Stock options	'	'	'
Number of Stock Options	'	'	'
Granted (in shares)	812,055	'	'

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended		98 Months Ended	101 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014
	segment
Segment Information	'	'	'	'
Number of geographic operating segments	2	'	'	'
Segment Information	'	'	'	'
Operating costs and expense	$47,293	$112,452	'	$1,519,576
Operating income (loss)	-47,293	-112,452	'	-1,519,576
Other income (expense)	-9,622	-15,635	'	-54,198
Net income (loss)	-56,915	-128,087	-1,516,859	-1,573,774
Additions to Property and Equipment, net	144,264	29,957	'	'
U.S. Gulf of Mexico	'	'	'	'
Segment Information	'	'	'	'
Operating costs and expense	31,027	23,105	'	'
Operating income (loss)	-31,027	-23,105	'	'
Additions to Property and Equipment, net	21,376	54,859	'	'
West Africa	'	'	'	'
Segment Information	'	'	'	'
Operating costs and expense	16,266	89,347	'	'
Operating income (loss)	-16,266	-89,347	'	'
Additions to Property and Equipment, net	$122,888	($24,902)	'	'