Concho Resources (CXO) 10-Q 7 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Nov. 04, 2013
Document Documentand Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'CXO	'
Entity Registrant Name	'CONCHO RESOURCES INC	'
Entity Central Index Key	'0001358071	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	105,061,575

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$22	$2,880
Accounts receivable, net of allowance for doubtful accounts:	'	'
Oil and natural gas	277,045	198,053
Joint operations and other	277,286	202,738
Derivative instruments	872	35,942
Deferred income taxes	33,150	0
Prepaid costs and other	19,337	19,269
Total current assets	607,712	458,882
Property and equipment:	'	'
Oil and natural gas properties, successful efforts method	10,852,246	9,455,599
Accumulated depletion and depreciation	-2,176,041	-1,565,316
Total oil and natural gas properties, net	8,676,205	7,890,283
Other property and equipment, net	111,705	103,141
Total property and equipment, net	8,787,910	7,993,424
Funds held in escrow	1,964	0
Deferred loan costs, net	76,377	77,609
Intangible asset - operating rights, net	28,980	30,076
Inventory	19,894	20,611
Noncurrent derivative instruments	0	2,769
Other assets	7,864	6,066
Total assets	9,530,701	8,589,437
Accounts payable:	'	'
Trade	36,813	31,144
Related parties	0	185
Bank overdrafts	69,444	24,275
Revenue payable	194,008	162,073
Accrued and prepaid drilling costs	323,928	351,919
Derivative instruments	71,364	1,584
Deferred income taxes	0	8,566
Other current liabilities	178,727	160,340
Total current liabilities	874,284	740,086
Long-term debt	3,588,650	3,101,103
Deferred income taxes	1,302,249	1,186,621
Noncurrent derivative instruments	24,049	12,049
Asset retirement obligations and other long-term liabilities	96,756	83,382
Commitments and contingencies (Note J)	'	'
Stockholders' equity:	'	'
Common stock, $0.001 par value; 300,000,000 authorized; 105,194,283 and 104,668,427 shares issued at September 30, 2013 and December 31, 2012, respectively	105	105
Additional paid-in capital	2,019,540	1,982,714
Retained earnings	1,635,777	1,490,563
Treasury stock, at cost; 125,580 and 86,861 shares at September 30, 2013 and December 31, 2012, respectively	-10,709	-7,186
Total stockholders' equity	3,644,713	3,466,196
Total liabilities and stockholders' equity	$9,530,701	$8,589,437

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	105,194,283	104,668,427
Treasury shares	125,580	86,861

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating revenues:	'	'	'	'
Oil sales	$553,068	$380,446	$1,412,887	$1,099,504
Natural gas sales	99,852	84,897	274,946	242,784
Total operating revenues	652,920	465,343	1,687,833	1,342,288
Operating costs and expenses:	'	'	'	'
Oil and natural gas production	120,231	87,964	328,295	251,641
Exploration and abandonments	10,992	6,958	37,797	27,335
Depreciation, depletion and amortization	200,625	148,145	557,775	408,675
Accretion of discount on asset retirement obligations	1,574	1,084	4,410	2,826
Impairments of long-lived assets	0	0	65,375	0
General and administrative (including non-cash stock-based compensation of $9,923 and $7,959 for the three months ended September 30, 2013 and 2012, respectively, and $25,278 and $21,434 for the nine months ended September 30, 2013 and 2012, respectively)	40,836	35,492	125,120	95,994
(Gain) loss on derivatives not designated as hedges	168,610	135,415	157,303	-109,542
Total operating costs and expenses	542,868	415,058	1,276,075	676,929
Income (loss) from continuing operations	110,052	50,285	411,758	665,359
Other income (expense):	'	'	'	'
Interest expense	-55,995	-51,337	-162,180	-129,073
Loss on extinguishment of debt	0	0	-28,616	0
Other, net	-1,941	-3,114	-1,806	-4,917
Total other expense	-57,936	-54,451	-192,602	-133,990
Income (loss) from continuing operations before income taxes	52,116	-4,166	219,156	531,369
Income tax (expense ) benefit	-21,695	995	-86,023	-204,327
Income (loss) from continuing operations	30,421	-3,171	133,133	327,042
Income from discontinued operations, net of tax	0	9,159	12,081	29,360
Net income	$30,421	$5,988	$145,214	$356,402
Basic earnings per share:	'	'	'	'
Income (loss) from continuing operations	$0.29	($0.03)	$1.27	$3.17
Income from discontinued operations, net of tax	$0	$0.09	$0.12	$0.29
Net income	$0.29	$0.06	$1.39	$3.46
Diluted earnings per share:	'	'	'	'
Income (loss) from continuing operations	$0.29	($0.03)	$1.27	$3.15
Income from discontinued operations, net of tax	$0	$0.09	$0.11	$0.28
Net income	$0.29	$0.06	$1.38	$3.43

Consolidated_Statements_of_Ope1

Consolidated Statements of Operations (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]	'	'	'	'
Non-cash stock-based compensation	$9,923	$7,959	$25,278	$21,434

Consolidated_Statement_of_Stoc

Consolidated Statement of Stockholders Equity (USD $)	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
In Thousands, except Share data
BALANCE at Dec. 31, 2012	$3,466,196	$105	$1,982,714	$1,490,563	($7,186)
BALANCE, Shares at Dec. 31, 2012	'	104,668,000	'	'	87,000
Net income	145,214	0	0	145,214	0
Stock options exercised	2,304	0	2,304	0	0
Stock options exercised, shares	139,111	139,000	'	'	0
Grants of restricted stock, shares	483,440	484,000	'	'	0
Cancellation of restricted stock, shares	'	-97,000	'	'	0
Stock-based compensation	25,278	0	25,278	0	0
Excess tax benefits related to stock-based compensation	9,244	0	9,244	0	0
Purchase of treasury stock	-3,523	0	0	0	-3,523
Purchase of treasury stock, shares	'	0	'	'	39,000
BALANCE at Sep. 30, 2013	$3,644,713	$105	$2,019,540	$1,635,777	($10,709)
BALANCE, Shares at Sep. 30, 2013	'	105,194,000	'	'	126,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:	'	'
Net income	$145,214	$356,402
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation, depletion and amortization	557,775	408,675
Accretion of discount on asset retirement obligations	4,410	2,826
Impairments of long-lived assets	65,375	0
Exploration and abandonments, including dry holes	13,159	15,224
Non-cash compensation expense	25,278	21,434
Deferred income taxes	75,808	203,107
Loss on sale of assets, net	1,717	285
(Gain) loss on derivatives not designated as hedges	157,303	-109,542
Discontinued operations	-12,250	28,591
Other non-cash items	17,020	9,066
Changes in operating assets and liabilities, net of acquisitions:	'	'
Accounts receivable	-113,226	-54,752
Prepaid costs and other	-1,866	-14,894
Inventory	434	-8,528
Accounts payable	4,407	-4,919
Revenue payable	44,983	-3,673
Other current liabilities	-40,897	-3,666
Net cash provided by operating activities	944,644	845,636
CASH FLOWS FROM INVESTING ACTIVITIES:	'	'
Capital expenditures on oil and natural gas properties	-1,426,349	-2,334,246
Additions to other property and equipment	-21,311	-47,489
Proceeds from the sale of assets	15,212	4,419
Funds held in escrow	-1,964	17,394
Settlements received from (paid on) derivatives not designated as hedges	-37,684	-7,485
Net cash used in investing activities	-1,472,096	-2,367,407
CASH FLOWS FROM FINANCING ACTIVITIES:	'	'
Proceeds from issuance of debt	3,283,875	3,856,500
Payments of debt	-2,798,400	-2,336,000
Exercise of stock options	2,304	8,062
Excess tax benefit from stock-based compensation	9,244	18,522
Payments for loan costs	-14,075	-23,926
Purchase of treasury stock	-3,523	-2,721
Bank overdrafts	45,169	1,283
Net cash provided by financing activities	524,594	1,521,720
Net increase (decrease) in cash and cash equivalents	-2,858	-51
Cash and cash equivalents at beginning of period	2,880	342
Cash and cash equivalents at end of period	$22	$291

Organization_and_nature_of_ope

Organization and nature of operations	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization and nature of operations	'
	Note A. Organization and nature of operations
	Concho Resources Inc. (the “Company”) is a Delaware corporation formed on February 22, 2006. The Company's principal business is the acquisition, development and exploration of oil and natural gas properties primarily located in the Permian Basin region of Southeast New Mexico and West Texas.

Summary_of_significant_account

Summary of significant accounting policies	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Summary of significant accounting policies	'
	Note B. Summary of significant accounting policies
	Principles of consolidation. The consolidated financial statements of the Company include the accounts of the Company and its wholly-owned subsidiaries. The Company consolidates the financial statements of these entities. All material intercompany balances and transactions have been eliminated.
	Use of estimates in the preparation of financial statements.  Preparation of financial statements in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from these estimates. Depletion of oil and natural gas properties is determined using estimates of proved oil and natural gas reserves. There are numerous uncertainties inherent in the estimation of quantities of proved reserves and in the projection of future rates of production and the timing of development expenditures. Similarly, evaluations for impairment of proved and unproved oil and natural gas properties are subject to numerous uncertainties including, among others, estimates of future recoverable reserves and commodity price outlooks. Other significant estimates include, but are not limited to, the asset retirement obligations, fair value of derivative financial instruments, fair value measurements for business combinations and fair value of stock-based compensation.
	Interim financial statements. The accompanying consolidated financial statements of the Company have not been audited by the Company's independent registered public accounting firm, except that the consolidated balance sheet at December 31, 2012 is derived from audited consolidated financial statements. In the opinion of management, the accompanying consolidated financial statements reflect all adjustments necessary to present fairly the Company's consolidated financial statements. All such adjustments are of a normal, recurring nature. In preparing the accompanying consolidated financial statements, management has made certain estimates and assumptions that affect reported amounts in the consolidated financial statements and disclosures of contingencies. Actual results may differ from those estimates. The results for interim periods are not necessarily indicative of annual results.
	Certain disclosures have been condensed in or omitted from these consolidated financial statements. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company's Annual Report on Form 10-K for the year ended December 31, 2012.
	Earnings per share. The Company grants non-vested restricted stock awards that meet the definition of a participating security. The Company calculates earnings per share (“EPS”) using the two-class method.
	Deferred loan costs. Deferred loan costs are stated at cost, net of amortization, which is computed using the effective interest and straight-line methods. The Company had deferred loan costs of $76.4 million and $77.6 million, net of accumulated amortization of $45.4 million and $38.8 million, at September 30, 2013 and December 31, 2012, respectively.
	Future amortization expense of deferred loan costs at September 30, 2013 was as follows:
	(in thousands)
	Remaining 2013		$	3,329
	2014			13,503
	2015			13,820
	2016			8,476
	2017			5,994
	2018			6,376
	Thereafter			24,879
		Total	$	76,377
	Intangible assets. The Company has capitalized certain operating rights acquired in an acquisition. The gross operating rights, which have no residual value, are amortized over the estimated economic life of 25 years. Impairment will be assessed if indicators of potential impairment exist or when there is a material change in the remaining useful economic life. The following table reflects the gross and net intangible assets at September 30, 2013 and December 31, 2012:
				September 30,		December 31,
	(in thousands)			2013		2012
	Gross intangible - operating rights		$	36,557	$	36,557
	Accumulated amortization			-7,577		-6,481
		Net intangible - operating rights	$	28,980	$	30,076
	The following table reflects amortization expense from continuing and discontinued operations for the three and nine months ended September 30, 2013 and 2012:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(in thousands)		2013		2012		2013		2012
	Amortization expense		$	365	$	388	$	1,096	$	1,162
	The following table reflects the estimated aggregate amortization expense for each of the periods presented below at September 30, 2013:
	(in thousands)
	Remaining 2013		$	365
	2014			1,461
	2015			1,461
	2016			1,461
	2017			1,461
	2018			1,461
	Thereafter			21,310
		Total	$	28,980
	Oil and natural gas sales and imbalances. Oil and natural gas revenues are recorded at the time of delivery to pipelines for the account of the purchaser or at the time of physical transfer to the purchaser. The Company follows the sales method of accounting for oil and natural gas sales, recognizing revenues based on the Company's share of actual proceeds from the oil and natural gas sold to purchasers. Oil and natural gas imbalances are generated on properties for which two or more owners have the right to take production “in-kind” and, in doing so, take more or less than their respective entitled percentage. Imbalances are tracked by well, but the Company does not record any receivable from or payable to the other owners unless the imbalance has reached a level at which it exceeds the remaining reserves in the respective well. If reserves are insufficient to offset the imbalance and the Company is in an overtake position, a liability is recorded for the amount of shortfall in reserves valued at a contract price or the market price in effect at the time the imbalance is generated. If the Company is in an undertake position, a receivable is recorded for an amount that is reasonably expected to be received, not to exceed the current market value of such imbalance. The Company has no material recorded or unrecorded imbalances.
	Treasury stock. Treasury stock purchases are recorded at cost. Upon reissuance, the cost of treasury shares held is reduced by the average purchase price per share of the aggregate treasury shares held.
	General and administrative expense. The Company receives fees for the operation of jointly-owned oil and natural gas properties and records such reimbursements as reductions of general and administrative expense. Such fees from continuing and discontinued operations totaled approximately $4.2 million and $4.4 million for the three months ended September 30, 2013 and 2012, respectively, and $13.5 million and $12.5 million for the nine months ended September 30, 2013 and 2012, respectively.
	Reclassifications. Certain prior period amounts have been reclassified to conform to the 2013 presentation. These reclassifications had no impact on net income, total stockholders' equity or cash flows.
	Recent accounting pronouncements. In December 2011, the Financial Accounting Standards Board (the “FASB”) issued amendments that require enhanced disclosure regarding financial instruments and derivative instruments that are either (i) offset in accordance with the current definition of “right of setoff” or the current balance sheet netting for derivative instruments allowed under current U.S. GAAP or (ii) subject to an enforceable master netting arrangement or similar agreement. The Company adopted this update on January 1, 2013, and the update did not have a significant impact on the consolidated financial statements.

Exploratory_well_costs

Exploratory well costs	9 Months Ended
	Sep. 30, 2013
Disclosure Exploratory Well Costs Capitalized Exploratory Well Activity [Abstract]	'
Exploratory well costs	'
	Note C. Exploratory well costs
	The Company capitalizes exploratory well costs until a determination is made that the well has either found proved reserves or that it is impaired. After an exploratory well has been completed and found oil and natural gas reserves, a determination may be pending as to whether the oil and natural reserves can be classified as proved. In those circumstances, the Company continues to capitalize the well or project costs pending the determination of proved status if (i) the well has found a sufficient quantity of reserves to justify its completion as a producing well and (ii) the Company is making sufficient progress assessing the reserves and the economic and operating viability of the project. The capitalized exploratory well costs are carried in unproved oil and natural gas properties. See Note R for the proved and unproved components of oil and natural gas properties. If the exploratory well is determined to be impaired, the well costs are charged to expense.
	The following table reflects the Company's capitalized exploratory well activity during the three and nine months ended September 30, 2013:
			Three Months Ended			Nine Months Ended
	(in thousands)		30-Sep-13			30-Sep-13
	Beginning capitalized exploratory well costs			$	180,433	$	118,806
		Additions to exploratory well costs pending the determination of proved reserves			262,743		806,327
		Reclassifications due to determination of proved reserves			-270,461		-752,349
		Exploratory well costs charged to expense			-		-69
	Ending capitalized exploratory well costs			$	172,715	$	172,715
	The following table provides an aging at September 30, 2013 and December 31, 2012 of capitalized exploratory well costs based on the date drilling was completed:
					September 30,		December 31,
	(in thousands)				2013		2012
	Exploratory wells in progress			$	27,176	$	22,837
	Capitalized exploratory well costs that have been capitalized for a period of one year or less				124,464		95,969
	Capitalized exploratory well costs that have been capitalized for a period greater than one year				21,075		-
		Total capitalized exploratory well costs		$	172,715	$	118,806
	Northern Midland Basin project. At September 30, 2013, the Company had approximately $6.3 million of suspended well costs greater than one year recorded for the first well in the Company's Northern Midland Basin project. The Company is currently in the process of drilling a second well to continue to evaluate the viability of this project.
	Southern Delaware Basin projects. At September 30, 2013, the Company had approximately $9.5 million of suspended well costs greater than one year recorded for two vertical wells where multiple zones are being evaluated in the Company's Southern Delaware Basin project. The Company is assessing options to drill horizontal laterals to continue evaluation of the targets.
	Other projects. At September 30, 2013, the Company had approximately $5.3 million of suspended well costs greater than one year recorded for three wells that have encountered technical difficulties that the Company plans to recomplete.
	Exploratory well counts. At September 30, 2013, the Company had 75 gross exploratory wells either drilling or waiting on results from completion and testing, of which 20 wells were in the Delaware Basin area, 28 wells were in the Texas Permian area and 27 wells were in the New Mexico Shelf area.

Acquisitions_and_business_comb

Acquisitions and business combinations	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]	'
Acquisitions and business combinations	'
	Note D. Acquisitions
	Three Rivers Acquisition. In July 2012, the Company acquired certain producing and non-producing assets from Three Rivers Operating Company LLC and certain affiliated entities (the “Three Rivers Acquisition”) for cash consideration of approximately $1.0 billion. The Three Rivers Acquisition was primarily funded with borrowings under the Company's credit facility. The Company's results of operations prior to July 2012 do not include results from the Three Rivers Acquisition.
	The following table reflects the fair value of the acquired asset and liabilities with the Three Rivers Acquisition:
	(in thousands)
	Fair value of net assets:
		Proved oil and natural gas properties		$	683,482
		Unproved oil and natural gas properties			359,109
			Total assets acquired		1,042,591
		Current liabilities, including current portion of asset retirement obligations			-2,229
		Asset retirement obligations assumed			-26,002
			Fair value of net assets acquired	$	1,014,360
	Fair value of consideration paid for net assets:
		Cash consideration		$	1,014,360
	PDC Acquisition. In February 2012, the Company acquired certain producing and non-producing assets from Petroleum Development Corporation (the “PDC Acquisition”) for cash consideration of approximately $189.2 million. The PDC Acquisition was primarily funded with borrowings under the Company's credit facility. The Company's results of operations prior to March 2012 do not include results from the PDC Acquisition.
	The following table reflects the fair value of the acquired assets and liabilities associated with the PDC Acquisition:
	(in thousands)
	Fair value of net assets:
		Current assets		$	2,366
		Proved oil and natural gas properties			159,314
		Unproved oil and natural gas properties			29,687
			Total assets acquired		191,367
		Current liabilities			-123
		Asset retirement obligations assumed			-2,050
			Fair value of net assets acquired	$	189,194
	Fair value of consideration paid for net assets:
		Cash consideration		$	189,194
	Pro forma data. The following unaudited pro forma combined condensed financial data for the nine months ended September 30, 2012, were derived from the historical financial statements of the Company giving effect to the Three Rivers Acquisition, as if it had occurred on January 1, 2012. The results of operations since the closing of the Three Rivers Acquisition in July 2012 are included in the Company's results of operations. The pro forma financial data does not include the results of operations for the PDC Acquisition, as the results of operations were deemed not to be material. The unaudited pro forma combined condensed financial data has been included for comparative purposes only and is not necessarily indicative of the results that might have occurred had the Three Rivers Acquisition taken place as of the date indicated and is not intended to be a projection of future results.
					Nine Months Ended
					September 30,
	(in thousands, except per share amounts)				2012
					(unaudited)
	Operating revenues				$	1,408,295
	Net income				$	336,712
	Earnings per common share:
		Basic			$	3.27
		Diluted			$	3.24

Asset_retirement_obligations

Asset retirement obligations	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Asset retirement obligations	'
	Note E. Asset retirement obligations
	The Company's asset retirement obligations represent the estimated present value of the estimated cash flows the Company will incur to plug, abandon and remediate its producing properties at the end of their productive lives, in accordance with applicable state laws. The Company does not provide for a market risk premium associated with asset retirement obligations because a reliable estimate cannot be determined. The Company has no assets that are legally restricted for purposes of settling asset retirement obligations.
	The Company's asset retirement obligation transactions during the three and nine months ended September 30, 2013 and 2012 are summarized in the table below:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Asset retirement obligations, beginning of period		$	96,347	$	68,089	$	86,261	$	59,685
		Liabilities incurred from new wells		1,775		3,053		5,024		6,319
		Liabilities assumed in acquisitions		-		26,986		282		29,113
		Accretion expense for continuing operations		1,574		1,084		4,410		2,826
		Accretion expense for discontinued operations		-		336		-		629
		Disposition of wells		-		-		-303		-66
		Liabilities settled upon plugging and abandoning wells		-897		-272		-2,542		-514
		Revision of estimates		561		3,151		6,228		4,435
	Asset retirement obligations, end of period		$	99,360	$	102,427	$	99,360	$	102,427

Incentive_plans

Incentive plans	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Incentive plans	'
	Note F. Incentive plans
	Defined contribution plan. The Company sponsors a 401(k) defined contribution plan for the benefit of substantially all employees. Currently, the Company matches 100 percent of employee contributions, not to exceed 10 percent of the employee's annual salary. The Company's contributions to the plan for the three months ended September 30, 2013 and 2012 were approximately $1.3 million and $1.1 million, respectively, and approximately $3.7 million and $3.0 million for the nine months ended September 30, 2013 and 2012, respectively.
	Stock incentive plan. The Company's 2006 Stock Incentive Plan, as amended and restated (the “Plan”), provides for granting stock options, restricted stock awards and performance awards to employees and individuals associated with the Company. The following table shows the number of existing awards and awards available under the Plan at September 30, 2013:
				Number of
				Common Shares
	Approved and authorized awards			7,500,000
	Restricted stock grants, net of forfeitures			-2,368,907
	Stock option grants, net of forfeitures			-3,463,720
	Performance unit grants (a)			-332,667
	Treasury shares			125,580
		Awards available for future grant		1,460,286
	(a)	This amount represents the 110,889 performance units granted multiplied by the maximum potential payout of 300 percent. The actual payout of shares may be between zero percent and 300 percent of the performance units granted depending on the Company's performance at the end of the performance period.
	Restricted stock awards. All restricted shares are treated as issued and outstanding in the accompanying consolidated balance sheets. If an employee terminates employment prior to the restriction lapse date, the awarded shares are forfeited and cancelled and are no longer considered issued and outstanding. A summary of the Company's restricted stock award activity for the nine months ended September 30, 2013 is presented below:
					Number of			Grant Date
					Restricted			Fair Value
					Shares			Per Share
	Restricted stock:
		Outstanding at December 31, 2012			1,072,527
			Shares granted		483,440		$	87.69
			Shares cancelled / forfeited		-96,695
			Lapse of restrictions		-220,710
		Outstanding at September 30, 2013			1,238,562
	The following table summarizes information about stock-based compensation for the Company's restricted stock awards activity under the Plan for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended						Nine Months Ended
					September 30,						September 30,
	(in thousands)					2013			2012			2013		2012
	Grant date fair value for awards during the period: (a)
		Employee grants			$	6,881		$	1,180		$	30,934	$	27,306
		Officer and director grants				-			290			12,445		18,521
			Total		$	6,881		$	1,470		$	43,379	$	45,827
	Stock-based compensation expense from restricted stock:
		Employee grants			$	5,116		$	3,854		$	12,511	$	9,617
		Officer and director grants				3,778			4,077			9,701		11,653
			Total		$	8,894		$	7,931		$	22,212	$	21,270
	Income taxes and other information:
		Income tax benefit related to restricted stock			$	3,399		$	3,032		$	8,491	$	8,131
		Deductions in current taxable income related to restricted stock			$	2,302		$	1,043		$	15,847	$	22,581
	(a)		The nine months ended September 30, 2013 includes the effects of $1 million due to modifications of certain stock-based awards.
	Stock option awards.  A summary of the Company's stock option award activity under the Plan for the nine months ended September 30, 2013 is presented below:
								Weighted
								Average
					Number of			Exercise
					Options			Price
	Stock options:
		Outstanding at December 31, 2012			429,879		$	20.28
			Options exercised		-139,111		$	16.57
		Outstanding at September 30, 2013			290,768		$	22.05
		Exercisable at end of period			290,768		$	22.05
	The following table summarizes information about the Company's exercisable stock options outstanding at September 30, 2013:
								Weighted
								Average			Weighted
			Range of					Remaining			Average
			Exercise			Number		Contractual			Exercise				Intrinsic
			Prices			Vested		Life			Price				Value
															(in thousands)
		Vested and exercisable options:
			$8.00			2,005		0.87 years			$	8		$	202
			$12.00			23,788		2.07 years			$	12			2,303
			12.85			15,000		3.88 years			$	12.85			1,439
			$20.00 - $23.00			192,895		4.78 years			$	21.4			16,862
			$28.00 - $37.27			57,080		4.66 years			$	31.34			4,422
						290,768		4.46 years			$	22.05		$	25,228
	The following table summarizes information about stock-based compensation for stock options for the three and nine months ended September 30, 2013 and 2012:
			Three Months Ended							Nine Months Ended
			September 30,							September 30,
(in thousands)					2013			2012			2013		2012
Stock-based compensation expense from stock options:
	Employee grants			$	-		$	7		$	2	$	24
	Officer and director grants				-			21			13		140
		Total		$	-		$	28		$	15	$	164
Income taxes and other information:
	Income tax benefit related to stock options			$	-		$	10		$	5	$	63
	Deductions in current taxable income related to stock options exercised			$	1,797		$	23,332		$	10,317	$	39,420
Performance unit awards. During the nine months ended September 30, 2013, the Company awarded performance units to its officers under the Plan. The number of shares of common stock that will ultimately be issued will be determined by a combination of (i) comparing the Company's total shareholder return relative to the total shareholder return of a predetermined group of peer companies at the end of the performance period and (ii) the Company's absolute total shareholder return at the end of the performance period. The performance period is 36 months. The grant date fair value was determined using the Monte Carlo simulation method and is being expensed ratably over the performance period.
The Company used the following assumptions to estimate the fair value of performance unit awards granted during the nine months ended September 30, 2013:
Risk-free interest rate							0.37%
Range of volatilities							31.5% - 45.1%
The following table summarizes the performance unit activity for the nine months ended September 30, 2013:
					Number of			Grant Date
					Units (a)			Fair Value
Performance units:
	Outstanding at December 31, 2012				-
		Units granted			110,889		$	111.4
	Outstanding at September 30, 2013				110,889
(a)	Reflects the amount of performance units granted. The actual payout of shares will be between zero and 300 percent of the performance units granted depending on the Company's performance at the end of the performance period.
The following table summarizes information about stock-based compensation expense for performance units for the three and nine months ended September 30, 2013:
					Three Months Ended						Nine Months Ended
					September 30,						September 30,
(in thousands)				2013					2013
Grant date fair value for awards during the period:
	Officer grants			$	-			$	12,353
Stock-based compensation expense from performance units:
	Officer grants			$	1,029			$	3,051
Income taxes:
	Income tax benefit related to performance units			$	394			$	1,167
Future stock-based compensation expense. The following table reflects the future stock-based compensation expense to be recorded for all the stock-based compensation awards that were outstanding at September 30, 2013:
				Restricted			Performance
(in thousands)				Stock			Units			Total
Remaining 2013			$	9,359		$	1,029		$	10,388
2014				27,262			4,118			31,380
2015				14,588			4,154			18,742
2016				5,245			-			5,245
2017				548			-			548
	Total		$	57,002		$	9,301		$	66,303

Disclosures_about_fair_value_o

Disclosures about fair value of financial instruments	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Disclosures about fair value of financial instruments	'
	Note G. Disclosures about fair value of financial instruments
	The Company uses a valuation framework based upon inputs that market participants use in pricing an asset or liability, which are classified into two categories: observable inputs and unobservable inputs. Observable inputs represent market data obtained from independent sources, whereas unobservable inputs reflect a company's own market assumptions, which are used if observable inputs are not reasonably available without undue cost and effort. These two types of inputs are further prioritized into the following fair value input hierarchy:
	Level 1:       Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. The Company considers active markets to be those in which transactions for the assets or liabilities occur in sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2:       Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. This category includes those derivative instruments that the Company values using observable market data. Substantially all of these inputs are observable in the marketplace throughout the full term of the derivative instrument, can be derived from observable data, or supported by observable levels at which transactions are executed in the marketplace. Level 2 instruments primarily include non-exchange traded derivatives such as over-the-counter commodity price swaps, basis swaps, collars and floors, investments and interest rate swaps. The Company's valuation models are primarily industry-standard models that consider various inputs including: (i) quoted forward prices for commodities, (ii) time value and (iii) current market and contractual prices for the underlying instruments, as well as other relevant economic measures.
	Level 3:       Measured based on prices or valuation models that require inputs that are both significant to the fair value measurement and less observable from objective sources (i.e., supported by little or no market activity). The Company's valuation models are primarily industry-standard models that consider various inputs including: (i) quoted forward prices for commodities, (ii) time value, (iii) volatility factors and (iv) current market and contractual prices for the underlying instruments, as well as other relevant economic measures.
	Financial Assets and Liabilities Measured at Fair Value
	The following table presents the carrying amounts and fair values of the Company's financial instruments at September 30, 2013 and December 31, 2012:
					30-Sep-13						31-Dec-12
					Carrying			Fair			Carrying			Fair
	(in thousands)				Value			Value			Value			Value
		Assets:
			Derivative instruments		$	872		$	872		$	38,711		$	38,711
		Liabilities:
			Derivative instruments		$	95,413		$	95,413		$	13,633		$	13,633
			Credit facility		$	207,600		$	210,666		$	304,000		$	299,679
			8.625% senior notes due 2017		$	-		$	-		$	297,103		$	323,471
			7.0% senior notes due 2021		$	600,000		$	657,000		$	600,000		$	669,000
			6.5% senior notes due 2022		$	600,000		$	643,500		$	600,000		$	660,000
			5.5% senior notes due 2022		$	600,000		$	598,500		$	600,000		$	633,000
			5.5% senior notes due 2023		$	1,581,050		$	1,530,625		$	700,000		$	733,250
	Cash and cash equivalents, accounts receivable, other current assets, accounts payable, interest payable and other current liabilities. The carrying amounts approximate fair value due to the short maturity of these instruments.
	Credit facility.  The fair value of the Company's credit facility is estimated by discounting the principal and interest payments at the Company's credit-adjusted discount rate at the reporting date and is determined utilizing inputs that are Level 2 measurements in the fair value hierarchy.
	Senior notes. The fair values of the Company's senior notes are based on quoted market prices. The debt securities are not actively traded and, therefore, are classified as Level 2 in the fair value hierarchy.
	Derivative instruments. The fair value of the Company's derivative instruments is estimated by management considering various factors, including closing exchange and over-the-counter quotations and the time value of the underlying commitments. Financial assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurement. The Company's assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of the fair value of assets and liabilities and their placement within the fair value hierarchy levels. The following table summarizes (i) the valuation of each of the Company's financial instruments by required fair value hierarchy levels and (ii) the gross fair value by the appropriate balance sheet classification, even when the derivative instruments are subject to netting arrangements and qualify for net presentation in the Company's consolidated balance sheets at September 30, 2013 and December 31, 2012. The Company nets the fair value of derivative instruments by counterparty in the Company's consolidated balance sheets.
						Fair Value Measurements Using															Net
						Quoted Prices													Gross		Fair Value
						in Active					Significant						Total		Amounts		Presented
						Markets for					Other			Significant			Fair Value		Offset in the		in the
						Identical					Observable			Unobservable			at		Consolidated		Consolidated
						Assets					Inputs			Inputs			September 30,		Balance		Balance
	(in thousands)					(Level 1)					(Level 2)			(Level 3)			2013		Sheet		Sheet
		Assets
			Current:(a)
				Commodity derivatives			$	-		$	12,880		$	-		$	12,880	$	-12,008	$	872
			Noncurrent:(b)
				Commodity derivatives				-			4,600			-			4,600		-4,600		-
		Liabilities
			Current:(a)
				Commodity derivatives				-			-83,372			-			-83,372		12,008		-71,364
			Noncurrent:(b)
				Commodity derivatives				-			-28,649			-			-28,649		4,600		-24,049
		Net derivative instruments					$	-		$	-94,541		$	-		$	-94,541	$	-	$	-94,541
						Fair Value Measurements Using															Net
						Quoted Prices													Gross		Fair Value
						in Active					Significant						Total		Amounts		Presented
						Markets for					Other			Significant			Fair Value		Offset in the		in the
						Identical					Observable			Unobservable			at		Consolidated		Consolidated
						Assets					Inputs			Inputs			December 31,		Balance		Balance
	(in thousands)					(Level 1)					(Level 2)			(Level 3)			2012		Sheet		Sheet
		Assets
			Current:(a)
				Commodity derivatives			$	-		$	56,471		$	-		$	56,471	$	-20,529	$	35,942
			Noncurrent:(b)
				Commodity derivatives				-			12,108			-			12,108		-9,339		2,769
		Liabilities
			Current:(a)
				Commodity derivatives				-			-22,113			-			-22,113		20,529		-1,584
			Noncurrent:(b)
				Commodity derivatives				-			-21,388			-			-21,388		9,339		-12,049
		Net derivative instruments					$	-		$	25,078		$	-		$	25,078	$	-	$	25,078
	Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis
	Certain assets and liabilities are reported at fair value on a nonrecurring basis in the Company's consolidated balance sheets.  The following methods and assumptions were used to estimate the fair values:
	Impairments of long-lived assets – The Company reviews its long-lived assets to be held and used, including proved oil and natural gas properties, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected undiscounted future net cash flows is less than the carrying amount of the assets. In this circumstance, the Company recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. The Company reviews its oil and natural gas properties by depletion base or by individual well for those wells not constituting part of a depletion base. For each property determined to be impaired, an impairment loss equal to the difference between the carrying value of the properties and the estimated fair value (discounted future cash flows) of the properties would be recognized at that time. Estimating future cash flows involves the use of judgments, including estimation of the proved and unproved oil and natural gas reserve quantities, timing of development and production, expected future commodity prices, capital expenditures and production costs.
The Company periodically reviews its proved oil and natural gas properties for impairment. Impairment expense is caused primarily due to declines in commodity prices and well performance. The Company did not recognize impairment charges for the three months ended September 30, 2012 and 2013 or for the nine months ended September 30, 2012. The Company recognized impairment charges for the nine months ended September 30, 2013 as follows:
						Estimated
			Carrying			Fair Value			Impairment
(in thousands)			Amount			(Level 3)			Expense
Nine Months Ended September 30, 2013		$	84,140		$	18,765		$	65,375

Derivative_financial_instrumen

Derivative financial instruments	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative financial instruments	'
	Note H. Derivative financial instruments
	The Company uses derivative financial instruments to manage its exposure to commodity price fluctuations. Commodity derivative instruments are used to (i) reduce the effect of the volatility of price changes on the oil and natural gas the Company produces and sells, (ii) support the Company's capital budget and expenditure plans and (iii) support the economics associated with acquisitions. The Company does not enter into derivative financial instruments for speculative or trading purposes. The Company may also enter into physical delivery contracts to effectively provide commodity price hedges. Because these contracts are not expected to be net cash settled, they are considered to be normal sales contracts and not derivatives. Therefore, these contracts are not recorded in the Company's consolidated financial statements.
	The Company does not designate its derivative instruments to qualify for hedge accounting. Accordingly, the Company reflects changes in the fair value of its derivative instruments in its statements of operations as they occur.
	The following table summarizes the gains (losses) reported in earnings related to the commodity derivative instruments for the three and nine months ended September 30, 2013 and 2012:
				Three Months Ended						Nine Months Ended
				September 30,						September 30,
	(in thousands)				2013			2012			2013			2012
	Gain (loss) on derivatives not designated as hedges:
		Oil derivatives		$	-169,049		$	-135,401		$	-172,698		$	109,386
		Natural gas derivatives			439			-14			15,395			156
			Total gain (loss) on derivatives not designated as hedges	$	-168,610		$	-135,415		$	-157,303		$	109,542
	The following table represents the Company's cash receipts from (payments on) derivatives not designated as hedges for the three and nine months ended September 30, 2013 and 2012:
				Three Months Ended						Nine Months Ended
				September 30,						September 30,
	(in thousands)				2013			2012			2013			2012
	Cash receipts from (payments on) derivatives not designated as hedges:
		Oil derivatives		$	-49,864		$	15,859		$	-42,528		$	-8,374
		Natural gas derivatives			4,589			280			4,844			889
			Total cash receipts from (payments on) derivatives not designated as hedges	$	-45,275		$	16,139		$	-37,684		$	-7,485
	Commodity derivative contracts at September 30, 2013. The following table sets forth the Company's outstanding derivative contracts at September 30, 2013. When aggregating multiple contracts, the weighted average contract price is disclosed. All of the Company's derivative contracts at September 30, 2013 are expected to settle by June 30, 2017.
					First		Second		Third		Fourth
					Quarter		Quarter		Quarter		Quarter		Total
	Oil Swaps: (a)
		2013:00:00
			Volume (Bbl)								4,614,000		4,614,000
			Price per Bbl							$	95.87	$	95.87
		2014:00:00
			Volume (Bbl)		4,277,000		3,848,000		3,560,000		3,355,000		15,040,000
			Price per Bbl	$	93.31	$	92.18	$	90.61	$	90.54	$	91.76
		2015:00:00
			Volume (Bbl)		3,154,000		2,984,000		2,858,000		2,721,000		11,717,000
			Price per Bbl	$	87.24	$	86.36	$	86.66	$	86.58	$	86.72
		2016:00:00
			Volume (Bbl)		108,000		108,000		108,000		105,000		429,000
			Price per Bbl	$	88.32	$	88.32	$	88.32	$	88.28	$	88.31
		2017:00:00
			Volume (Bbl)		84,000		84,000		-		-		168,000
			Price per Bbl	$	87	$	87	$	-	$	-	$	87
	Oil Basis Swaps: (b)
		2013:00:00
			Volume (Bbl)								3,404,000		3,404,000
			Price per Bbl							$	-1.12	$	-1.12
		2014:00:00
			Volume (Bbl)		2,790,000		2,821,000		1,932,000		1,932,000		9,475,000
			Price per Bbl	$	-0.46	$	-0.46	$	-0.45	$	-0.45	$	-0.46
	Natural Gas Swaps: (c)
		2013:00:00
			Volume (MMBtu)								6,992,000		6,992,000
			Price per MMBtu							$	4.25	$	4.25
	Natural Gas Collars: (d)
		2014:00:00
			Volume (MMBtu)		5,400,000		5,460,000		5,520,000		5,520,000		21,900,000
			Ceiling price per MMBtu	$	4.4	$	4.4	$	4.4	$	4.4	$	4.4
			Floor price per MMBtu	$	3.85	$	3.85	$	3.85	$	3.85	$	3.85
	Natural Gas Basis Swaps: (e)
		2013:00:00
			Volume (MMBtu)								6,440,000		6,440,000
			Price per MMBtu							$	-0.15	$	-0.15
	(a) The index prices for the oil price swaps are based on the NYMEX – West Texas Intermediate (“WTI”) monthly average futures price.
	(b) The basis differential price is between Midland – WTI and Cushing – WTI.
	(c) The index prices for the natural gas price swaps are based on the NYMEX – Henry Hub last trading day futures price.
	(d) The index prices for the natural gas collars are based on the El Paso Permian delivery point.
	(e) The basis differential price is between the El Paso Permian delivery point and NYMEX – Henry Hub delivery point.

Debt

Debt	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Debt	'
	Note I. Debt
	The Company's debt consisted of the following at September 30, 2013 and December 31, 2012:
						September 30,			December 31,
	(in thousands)					2013			2012
	Credit facility				$	207,600		$	304,000
	8.625% unsecured senior notes due 2017					-			300,000
	7.0% unsecured senior notes due 2021					600,000			600,000
	6.5% unsecured senior notes due 2022					600,000			600,000
	5.5% unsecured senior notes due 2022					600,000			600,000
	5.5% unsecured senior notes due 2023					1,550,000			700,000
	Unamortized original issue premium (discount), net					31,050			-2,897
		Less: current portion				-			-
			Total long-term debt		$	3,588,650		$	3,101,103
	Credit facility. The Company's credit facility, as amended (the “Credit Facility”), has a maturity date of April 25, 2016. The Company's borrowing base is $3.0 billion until the next scheduled borrowing base redetermination in April 2014, and commitments from the Company's bank group total $2.5 billion. Between scheduled borrowing base redeterminations, the Company and the lenders (requiring a 66 2/3 percent vote) may each request one special redetermination.
	Advances on the Credit Facility bear interest, at the Company's option, based on (i) the prime rate of JPMorgan Chase Bank (“JPM Prime Rate”) (3.25 percent at September 30, 2013) or (ii) a Eurodollar rate (substantially equal to the LIBOR). At September 30, 2013, the interest rates of Eurodollar rate advances and JPM Prime Rate advances varied, with interest margins ranging from 150 to 250 basis points and 50 to 150 basis points per annum, respectively, depending on the debt balance outstanding on the Credit Facility. At September 30, 2013, the Company paid commitment fees on the unused portion of the available commitments ranging from 37.5 to 50 basis points per annum.
	The Credit Facility also includes a same-day advance facility under which the Company may borrow funds from the administrative agent. Same-day advances cannot exceed $25 million, and the maturity dates cannot exceed fourteen days. The interest rate on the same-day advance facility is the JPM Prime Rate plus the applicable interest margin.
	The Company's obligations under the Credit Facility are secured by a first lien on substantially all of its oil and natural gas properties. In addition, all of the Company's subsidiaries are guarantors and have had their equity pledged to secure borrowings under the Credit Facility.
	The Credit Facility contains various restrictive covenants and compliance requirements which include:
	maintenance of certain financial ratios, including (i) maintenance of a quarterly ratio of total debt to last twelve months of consolidated earnings before interest expense, income taxes, depletion, depreciation, and amortization, exploration expense and other noncash income and expenses to be no greater than 4.0 to 1.0, and (ii) maintenance of a ratio of current assets to current liabilities, excluding noncash assets and liabilities related to financial derivatives and asset retirement obligations and including the unfunded amounts under the Credit Facility, to be not less than 1.0 to 1.0;
	limits on the incurrence of additional indebtedness and certain types of liens;
	restrictions as to mergers, combinations and dispositions of assets; and
	limitations on the payment of cash dividends.
	Senior notes. Interest on the Company's senior notes is paid in arrears semi-annually. The senior notes are fully and unconditionally guaranteed on a senior unsecured basis by all subsidiaries of the Company, subject to customary release provisions as described in Note P.
	On June 3, 2013, the Company received tenders and consents from the holders of approximately $225.6 million in aggregate principal amount, or approximately 75.2 percent, of its outstanding 8.625% senior notes due 2017 (the “8.625% Notes”) in connection with a cash tender offer for any and all of the 8.625% Notes at a price of 106.922 percent of the unpaid principal amount.
	On June 21, 2013, the Company redeemed the remaining outstanding 8.625% Notes not purchased in the tender offer at a redemption price of 106.516 percent of the unpaid principal amount plus accrued and unpaid interest through June 20, 2013.
	The Company recorded a loss on extinguishment of debt related to the tender offer and redemption of its 8.625% Notes of approximately $28.6 million for the nine months ended September 30, 2013. This amount includes approximately $20.4 million associated with the premium paid for the tender offer and redemption of the notes, approximately $5.5 million of unamortized deferred loan costs and approximately $2.7 million of unamortized discount.
	On June 4, 2013, the Company completed the issuance of an additional $850 million in principal amount of its 5.5% senior notes due 2023 (the “Offering”) at 103.75 percent of par (resulting in a 4.884% yield) for net proceeds of approximately $867.8 million. The Company used a portion of the net proceeds from the Offering to fund the tender offer and redemption of the 8.625% Notes and to pay down amounts outstanding on the Credit Facility.
	At September 30, 2013, the Company was in compliance with the covenants under its debt instruments.
	Future benefit to interest expense from original issue premium at September 30, 2013 was as follows:
	(in thousands)
	Remaining 2013			$		629
	2014					2,602
	2015					2,747
	2016					2,900
	2017					3,062
	2018					3,233
	Thereafter					15,877
		Total		$		31,050
	Principal maturities of debt. Principal maturities of long-term debt outstanding at September 30, 2013 were as follows:
	(in thousands)
	Remaining 2013			$		-
	2014					-
	2015					-
	2016					207,600
	2017					-
	2018					-
	Thereafter					3,350,000
		Total		$		3,557,600
	Interest expense. The following amounts have been incurred and charged to interest expense for the three and nine months ended September 30, 2013 and 2012:
							Three Months Ended					Nine Months Ended
							September 30,					September 30,
	(in thousands)							2013			2012		2013		2012
	Cash payments for interest						$	43,868		$	48,203	$	145,980	$	115,731
	Amortization of original issue discount (premium)							-620			117		-619		342
	Amortization of deferred loan origination costs							3,311			3,114		9,844		8,724
	Net changes in accruals							9,436			-97		6,975		4,276
		Total interest expense					$	55,995		$	51,337	$	162,180	$	129,073

Commitments_and_contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and contingencies	'
	Note J. Commitments and contingencies
	Severance agreements. The Company has entered into severance and change in control agreements with all of its officers. The current annual salaries for the Company's officers covered under such agreements total approximately $5.6 million.
	Indemnifications. The Company has agreed to indemnify its directors and officers with respect to claims and damages arising from certain acts or omissions taken in such capacity.
	Legal actions. The Company is a party to proceedings and claims incidental to its business. While many of these matters involve inherent uncertainty, the Company believes that the amount of the liability, if any, ultimately incurred with respect to any such proceedings or claims will not have a material adverse effect on the Company's consolidated financial position as a whole or on its liquidity, capital resources or future results of operations. The Company will continue to evaluate proceedings and claims involving the Company on a regular basis and will establish and adjust any reserves as appropriate to reflect its assessment of the then current status of the matters.
	Contractual drilling commitments.  The Company periodically enters into contractual arrangements under which the Company is committed to expend funds to drill wells in the future, including agreements to secure drilling rig services, which require the Company to make future minimum payments to the rig operators. The Company records drilling commitments in the periods in which well capital is incurred or rig services are provided. The following table summarizes the Company's future drilling commitments at September 30, 2013:
			Payments Due By Period
							Less than		3-Jan		5-Mar		More than
	(in thousands)			Total			1 year		years		years		5 years
	Contractual drilling commitments		$	8,084		$	8,084	$	-	$	-	$	-
	Operating leases. The Company leases vehicles, equipment and office facilities under non-cancellable operating leases. Lease payments associated with these operating leases for the three months ended September 30, 2013 and 2012 were approximately $1.5 million and $1.3 million, respectively, and approximately $4.2 million and $3.6 million for the nine months ended September 30, 2013 and 2012, respectively.
	Future minimum lease commitments under non-cancellable operating leases at September 30, 2013 were as follows:
	(in thousands)
	Remaining 2013			$	1,508
	2014				5,372
	2015				4,146
	2016				2,778
	2017				750
	2018				441
	Thereafter				1,247
		Total		$	16,242

Income_taxes

Income taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income taxes	'
	Note K. Income taxes
	The Company uses an asset and liability approach for financial accounting and reporting for income taxes. The Company's objectives of accounting for income taxes are to recognize (i) the amount of taxes payable or refundable for the current year and (ii) deferred tax liabilities and assets for the future tax consequences of events that have been recognized in its financial statements or tax returns. The Company and its subsidiaries file a federal income tax return on a consolidated basis. The tax returns and the amount of taxable income or loss are subject to examination by federal and state taxing authorities. At September 30, 2013, the Company had current income taxes receivable of approximately $3.8 million. At September 30, 2013 and December 31, 2012, the Company had current income taxes payable of approximately $0.4 million and $2.1 million, respectively.
	The Company continually assesses both positive and negative evidence to determine whether it is more likely than not that deferred tax assets can be realized prior to their expiration. Management monitors company-specific, oil and natural gas industry and worldwide economic factors and assesses the likelihood that the Company's net operating loss carryforwards, if any, and other deferred tax attributes in the United States, state, and local tax jurisdictions will be utilized prior to their expiration. At September 30, 2013 and December 31, 2012, the Company had no valuation allowances related to its deferred tax assets.
	At September 30, 2013, the Company did not have any significant uncertain tax positions requiring recognition in the financial statements. The tax years 2009 through 2012 remain subject to examination by the major tax jurisdictions.
	Income tax provision. The Company's income tax provision (benefit) and amounts separately allocated were attributable to the following items for the three and nine months ended September 30, 2013 and 2012:
							Three Months Ended						Nine Months Ended
							September 30,						September 30,
	(in thousands)							2013			2012			2013			2012
	Income (loss) from continuing operations						$	21,695		$	-995		$	86,023		$	204,327
	Income from discontinued operations							-			5,150			7,518			16,508
	Changes in stockholders' equity:
		Excess tax benefits related to stock-based compensation						-5,081			-8,129			-9,244			-18,522
							$	16,614		$	-3,974		$	84,297		$	202,313
	The Company's income tax provision (benefit) attributable to income from continuing operations consisted of the following for the three and nine months ended September 30, 2013 and 2012:
							Three Months Ended						Nine Months Ended
							September 30,						September 30,
	(in thousands)							2013			2012			2013			2012
	Current:
		U.S. federal					$	-3,661		$	-3,259		$	8,427		$	-1,155
		U.S. state and local						-106			555			1,788			2,375
			Total current income tax provision (benefit)					-3,767			-2,704			10,215			1,220
	Deferred:
		U.S. federal						23,652			2,240			67,529			178,766
		U.S. state and local						1,810			-531			8,279			24,341
			Total deferred income tax provision					25,462			1,709			75,808			203,107
				Total income tax provision (benefit) attributable to income from
					continuing operations		$	21,695		$	-995		$	86,023		$	204,327
	The reconciliation between the income tax expense (benefit) computed by multiplying pretax income (loss) from continuing operations by the United States federal statutory rate and the reported amounts of income tax expense (benefit) from continuing operations is as follows:
							Three Months Ended						Nine Months Ended
							September 30,						September 30,
	(in thousands)							2013			2012			2013			2012
	Income (loss) at U.S. federal statutory rate						$	18,241		$	-1,458		$	76,705		$	185,979
	State income taxes (net of federal tax effect)							1,726			-159			7,161			17,245
	Revision of previous tax estimates							1,273			219			1,273			219
	Statutory depletion							58			-91			-21			-207
	Nondeductible expense & other							397			494			905			1,091
		Income tax expense (benefit)					$	21,695		$	-995		$	86,023		$	204,327
	Effective tax rate							41.60%			23.90%			39.30%			38.50%
	The Company's income tax provision attributable to income from discontinued operations consisted of the following for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended						Nine Months Ended
					September 30,						September 30,
	(in thousands)				2013			2012			2013			2012
	Current:
		U.S. federal			$	-		$	4,589		$	144		$	14,729
		U.S. state and local				-			25			25			82
			Total current income tax provision			-			4,614			169			14,811
	Deferred:
		U.S. federal				-			-107			6,397			-366
		U.S. state and local				-			643			952			2,063
			Total deferred income tax provision			-			536			7,349			1,697
				Total income tax provision attributable to
				income from discontinued operations	$	-		$	5,150		$	7,518		$	16,508

Related_party_transactions

Related party transactions	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]	'
Related party transactions	'
	Note L. Related party transactions
	The following tables summarize charges incurred with and payments made to related parties and reported in the Company's consolidated statements of operations, as well as outstanding payables included in the consolidated balance sheets for the periods presented:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Royalties paid to a partnership in which a director has an ownership interest (a)		$	2,010	$	525	$	4,694	$	1,820
	Royalties paid to a director and certain officers of the Company (b)		$	12	$	-	$	33	$	-
	Amounts paid under consulting agreement with Steven L. Beal (c)		$	745	$	60	$	865	$	180
							September 30,		December 31,
	(in thousands)						2013		2012
	Amounts included in accounts payable - related parties:
		Royalty interests of a director of the Company (a)					$	0	$	185
	Royalties paid on certain properties to a partnership of which a director is the general partner and owns a 3.5 percent partnership interest.
	Payments made to a director and certain officers who directly own overriding royalty interests in properties owned by the Company.
	On June 30, 2009, Steven L. Beal, the Company's then-president and chief operating officer, retired from such positions. On June 9, 2009, the Company entered into a consulting agreement (the “Consulting Agreement”) with Mr. Beal, under which Mr. Beal began serving as a consultant to the Company on July 1, 2009. During the term of the consulting relationship, Mr. Beal received a consulting fee of $20,000 per month and a monthly reimbursement for his medical and dental coverage costs. In August 2013, the Company and Mr. Beal mutually terminated the Consulting Agreement in exchange for the payment to Mr. Beal of $720,000, which termination and payment were approved by the disinterested members of the Company's Board of Directors.
	In June 2013, in connection with the tender offer for the 8.625% Notes, certain directors and officers received an aggregate amount of approximately $1.3 million for the 8.625% Notes they owned.

Discontinued_operations

Discontinued operations	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]	'
Discontinued operations	'
	Note M. Discontinued operations
	In December 2012, the Company closed the sale of certain of its non-core assets for cash consideration of approximately $503.1 million, which resulted in a pre-tax gain of approximately $0.9 million. As a result of post-closing adjustments during the nine months ended September 30, 2013, the Company made adjustments to its pre-tax gain of approximately $19.6 million. The Company reflected the results of operations of this divestiture as discontinued operations, rather than as a component of continuing operations. The following table represents the components of the Company's discontinued operations for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended				Nine Months Ended
					September 30,				September 30,
	(in thousands)				2013		2012		2013	2012
	Operating revenues:
		Oil sales		$	-	$	26,616	$	-	$	82,518
		Natural gas sales			-		5,588		-		13,342
			Total operating revenues		-		32,204		-		95,860
	Operating costs and expenses:
		Oil and natural gas production			-		8,702		-		24,864
		Depreciation, depletion and amortization (a)			-		9,476		-		26,265
		Accretion of discount on asset retirement obligations (a)			-		336		-		629
		General and administrative (b)			-		-619		-		-1,766
			Total operating costs and expenses		-		17,895		-		49,992
	Income from operations				-		14,309		-		45,868
	Other income (expense):
		Gain on disposition of assets, net (a)			-		-		19,599		-
	Income from discontinued operations before income taxes				-		14,309		19,599		45,868
	Income tax expense:
		Current			-		-4,614		-169		-14,811
		Deferred (a)			-		-536		-7,349		-1,697
	Income from discontinued operations, net of tax			$	-	$	9,159	$	12,081	$	29,360
	(a)		Represents the significant non-cash components of discontinued operations.
	(b)		Represents the fees received from third-parties for operating oil and natural gas properties that were sold. The Company reflects these fees as a reduction of general and administrative expenses.

Net_income_per_share

Net income per share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]	'
Net income per share	'
	Note N. Net income per share
	The Company uses the two-class method of calculating net income (loss) per share because certain of the Company's unvested share-based awards qualify as participating securities. Participating securities participate in income proportionate to the weighted average number of outstanding common shares, but are not assumed to participate in the Company's net losses because they are not contractually obligated to do so. Accordingly, allocations of earnings to participating securities are included in the Company's calculations of basic and diluted earnings per share from continuing operations, discontinued operations and net income (loss) attributable to common stockholders.
	The following tables reconcile the Company's net income (loss) from continuing operations, income from discontinued operations and net income (loss) attributable to common stockholders to the basic and diluted earnings used to determine the Company's net income per share amounts for the three and nine months ended September 30, 2013 and 2012, respectively, under the two-class method:
						Three Months Ended								Nine Months Ended
						30-Sep-13								30-Sep-13
					Continuing			Discontinued					Continuing		Discontinued
	(in thousands, except per share amounts)				Operations			Operations			Total		Operations		Operations		Total
	Income as reported				$	30,421		$	-		$	30,421	$	133,133	$	12,081	$	145,214
	Participating basic earnings					-357			-			-357		-1,421		-129		-1,550
		Basic income attributable to common
			stockholders			30,064			-			30,064		131,712		11,952		143,664
	Reallocation of participating earnings					-			-			-		2		-		2
		Diluted income attributable to common
			stockholders		$	30,064		$	-		$	30,064	$	131,714	$	11,952	$	143,666
	Income per common share:
		Basic			$	0.29		$	-		$	0.29	$	1.27	$	0.12	$	1.39
		Diluted			$	0.29		$	-		$	0.29	$	1.27	$	0.11	$	1.38
						Three Months Ended								Nine Months Ended
						30-Sep-12								30-Sep-12
					Continuing			Discontinued					Continuing		Discontinued
	(in thousands, except per share amounts)				Operations			Operations			Total		Operations		Operations		Total
	Income (loss) as reported				$	-3,171		$	9,159		$	5,988	$	327,042	$	29,360	$	356,402
	Participating basic earnings					-			-			-		-		-		-
		Basic income (loss) attributable to
			common stockholders			-3,171			9,159			5,988		327,042		29,360		356,402
	Reallocation of participating earnings					-			-			-		-		-		-
		Diluted income (loss) attributable to
			common stockholders		$	-3,171		$	9,159		$	5,988	$	327,042	$	29,360	$	356,402
	Income (loss) per common share:
		Basic			$	-0.03		$	0.09		$	0.06	$	3.17	$	0.29	$	3.46
		Diluted			$	-0.03		$	0.09		$	0.06	$	3.15	$	0.28	$	3.43
	The following table is a reconciliation of the basic weighted average common shares outstanding to diluted weighted average common shares outstanding for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended				Nine Months Ended
					September 30,				September 30,
	(in thousands)				2013		2012		2013		2012
	Weighted average common shares outstanding:
		Basic			103,801		103,292		103,709		103,088
			Dilutive common stock options		157		323		173		399
			Dilutive restricted stock		-		425		-		411
			Dilutive performance units		-		-		-		-
		Diluted			103,958		104,040		103,882		103,898
	The following table is a summary of the common stock options, restricted stock and performance units which were not included in the computation of diluted net income per share, as inclusion would be antidilutive:
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Number of antidilutive common shares:
		Antidilutive common stock options		-		-		-		-
		Antidilutive restricted stock		2		31		7		126
		Antidilutive performance units		111		-		111		-

Other_current_liabilities

Other current liabilities	9 Months Ended
	Sep. 30, 2013
Other Liabilities Disclosure [Abstract]	'
Other current liabilities	'
	Note O. Other current liabilities
	The following table provides the components of the Company's other current liabilities at September 30, 2013 and December 31, 2012:
					September 30,		December 31,
	(in thousands)				2013		2012
	Other current liabilities:
		Accrued production costs		$	53,642	$	52,825
		Payroll related matters			21,360		16,365
		Accrued interest			79,460		64,304
		Settlements due on derivatives not designated as hedges			17,304		-
		Acquisition and divestiture settlements			-		18,100
		Income taxes payable			425		2,141
		Asset retirement obligations			2,674		3,308
		Other			3,862		3,297
			Other current liabilities	$	178,727	$	160,340

Subsidiary_guarantors

Subsidiary guarantors	9 Months Ended
	Sep. 30, 2013
Guarantees [Abstract]	'
Subsidiary guarantors	'
	Note P. Subsidiary guarantors
	As of September 30, 2013, all of the Company's wholly-owned subsidiaries have fully and unconditionally guaranteed the Company's senior notes. The indentures governing the Company's senior notes provide that the guarantees of its subsidiary guarantors will be released in certain customary circumstances, including (i) in connection with any sale, exchange or other disposition, whether by merger, consolidation or otherwise, of the capital stock of that guarantor to a person that is not the Company or a restricted subsidiary of the Company, such that, after giving effect to such transaction, such guarantor would no longer constitute a subsidiary of the Company, (ii) in connection with any sale, exchange or other disposition (other than a lease) of all or substantially all of the assets of that guarantor to a person that is not the Company or a restricted subsidiary of the Company, (iii) upon the merger of a guarantor into the Company or any other guarantor or the liquidation or dissolution of a guarantor, (iv) if the Company designates any restricted subsidiary that is a guarantor to be an unrestricted subsidiary in accordance with the indenture, (v) upon legal defeasance or satisfaction and discharge of the indenture and (vi) upon written notice of such release or discharge by the Company to the trustee following the release or discharge of all guarantees by such guarantor of any indebtedness that resulted in the creation of such guarantee, except a discharge or release by or as a result of payment under such guarantee.
	See Note I for a summary of the Company's senior notes. In accordance with practices accepted by the U.S. Securities and Exchange Commission, the Company has prepared condensed consolidating financial statements in order to quantify the assets, results of operations and cash flows of such subsidiaries as subsidiary guarantors.
	In 2012, one of the entities included in the Company's consolidated financial statements was formed to effectuate a tax-free exchange of assets. This entity did not guarantee the Company's senior notes and is referred to as a “Non-Guarantor Subsidiary” in the tables below.
	The following condensed consolidating balance sheets at September 30, 2013 and December 31, 2012, condensed consolidating statements of operations for the three and nine months ended September 30, 2013 and 2012 and condensed consolidating statements of cash flows for the nine months ended September 30, 2013 and 2012, present financial information for Concho Resources Inc. as the Parent on a stand-alone basis (carrying any investments in subsidiaries under the equity method), financial information for the subsidiary guarantors on a stand-alone basis and the consolidation and elimination entries necessary to arrive at the information for the Company on a consolidated basis. All current and deferred income taxes are recorded on Concho Resources Inc., as the subsidiaries are flow-through entities for income tax purposes. The subsidiary guarantors are not restricted from making distributions to the Company.
	Condensed Consolidating Balance Sheet
	30-Sep-13
					Parent			Subsidiary			Consolidating
	(in thousands)				Issuer			Guarantors			Entries			Total
	ASSETS
	Accounts receivable - related parties			$	6,158,999		$	1,279,039		$	-7,438,038		$	-
	Other current assets				36,298			571,414			-			607,712
	Oil and natural gas properties, net				-			8,676,205			-			8,676,205
	Property and equipment, net				-			111,705			-			111,705
	Investment in subsidiaries				3,735,429			-			-3,735,429			-
	Other long-term assets				76,376			58,703			-			135,079
		Total assets		$	10,007,102		$	10,697,066		$	-11,173,467		$	9,530,701
	LIABILITIES AND EQUITY
	Accounts payable - related parties			$	1,279,039		$	6,158,999		$	-7,438,038		$	-
	Other current liabilities				168,402			705,882			-			874,284
	Other long-term liabilities				1,326,298			96,756			-			1,423,054
	Long-term debt				3,588,650			-			-			3,588,650
	Equity				3,644,713			3,735,429			-3,735,429			3,644,713
		Total liabilities and equity		$	10,007,102		$	10,697,066		$	-11,173,467		$	9,530,701
	Condensed Consolidating Balance Sheet
	31-Dec-12
					Parent			Subsidiary			Consolidating
	(in thousands)				Issuer			Guarantors			Entries			Total
	ASSETS
	Accounts receivable - related parties			$	5,839,995		$	2,416,697		$	-8,256,692		$	-
	Other current assets				46,737			412,145			-			458,882
	Oil and natural gas properties, net				-			7,890,283			-			7,890,283
	Property and equipment, net				-			103,141			-			103,141
	Investment in subsidiaries				3,146,918			-			-3,146,918			-
	Other long-term assets				80,378			56,753			-			137,131
		Total assets		$	9,114,028		$	10,879,019		$	-11,403,610		$	8,589,437
	LIABILITIES AND EQUITY
	Accounts payable - related parties			$	1,271,563		$	6,985,314		$	-8,256,692		$	185
	Other current liabilities				76,496			663,405			-			739,901
	Other long-term liabilities				1,198,670			83,382			-			1,282,052
	Long-term debt				3,101,103			-			-			3,101,103
	Equity				3,466,196			3,146,918			-3,146,918			3,466,196
		Total liabilities and equity		$	9,114,028		$	10,879,019		$	-11,403,610		$	8,589,437
	Condensed Consolidating Statement of Operations
	Three Months Ended September 30, 2013
					Parent			Subsidiary			Consolidating
	(in thousands)				Issuer			Guarantors			Entries			Total
	Total operating revenues			$	-		$	652,920		$	-		$	652,920
	Total operating costs and expenses				-169,935			-372,933			-			-542,868
		Income (loss) from continuing operations			-169,935			279,987			-			110,052
	Interest expense				-55,995			-			-			-55,995
	Other, net				278,046			-1,996			-277,991			-1,941
		Income from continuing operations before income taxes			52,116			277,991			-277,991			52,116
	Income tax expense				-21,695			-			-			-21,695
		Net income		$	30,421		$	277,991		$	-277,991		$	30,421
	Condensed Consolidating Statement of Operations
	Three Months Ended September 30, 2012
						Parent			Subsidiary			Subsidiary			Consolidating
	(in thousands)					Issuer			Guarantors			Non-Guarantor			Entries		Total
	Total operating revenues				$	-		$	458,001		$	7,342		$	-	$	465,343
	Total operating costs and expenses					-135,637			-273,701			-5,720			-		-415,058
		Income (loss) from continuing operations				-135,637			184,300			1,622			-		50,285
	Interest expense					-51,337			-			-			-		-51,337
Other, net					197,117			2,309			-6,043			-196,497		-3,114
	Income (loss) from continuing
		operations before income taxes			10,143			186,609			-4,421			-196,497		-4,166
Income tax benefit					995			-			-			-		995
	Income (loss) from continuing operations				11,138			186,609			-4,421			-196,497		-3,171
Income (loss) from discontinued
	operations, net of tax				-5,150			14,309			-			-		9,159
	Net income (loss)			$	5,988		$	200,918		$	-4,421		$	-196,497	$	5,988
Condensed Consolidating Statement of Operations
Nine Months Ended September 30, 2013
				Parent			Subsidiary			Consolidating
(in thousands)				Issuer			Guarantors			Entries			Total
Total operating revenues			$	-		$	1,687,833		$	-		$	1,687,833
Total operating costs and expenses				-159,017			-1,117,058			-			-1,276,075
	Income (loss) from continuing operations			-159,017			570,775			-			411,758
Interest expense				-162,180			-			-			-162,180
Loss on extinguishment of debt				-28,616			-			-			-28,616
Other, net				588,568			-1,863			-588,511			-1,806
	Income from continuing operations before income taxes			238,755			568,912			-588,511			219,156
Income tax expense				-86,023			-			-			-86,023
	Income from continuing operations			152,732			568,912			-588,511			133,133
Income (loss) from discontinued operations, net of tax				-7,518			19,599			-			12,081
	Net income		$	145,214		$	588,511		$	-588,511		$	145,214
Condensed Consolidating Statement of Operations
Nine Months Ended September 30, 2012
					Parent			Subsidiary			Subsidiary			Consolidating
(in thousands)					Issuer			Guarantors			Non-Guarantor			Entries		Total
Total operating revenues				$	-		$	1,334,946		$	7,342		$	-	$	1,342,288
Total operating costs and expenses					108,776			-779,985			-5,720			-		-676,929
	Income from continuing operations				108,776			554,961			1,622			-		665,359
Interest expense					-129,073			-			-			-		-129,073
Other, net					597,534			522			-6,043			-596,930		-4,917
	Income (loss) from continuing
		operations before income taxes			577,237			555,483			-4,421			-596,930		531,369
Income tax expense					-204,327			-			-			-		-204,327
	Income (loss) from continuing operations				372,910			555,483			-4,421			-596,930		327,042
Income (loss) from discontinued
	operations, net of tax				-16,508			45,868			-			-		29,360
	Net income (loss)			$	356,402		$	601,351		$	-4,421		$	-596,930	$	356,402
Condensed Consolidating Statement of Cash Flows
Nine Months Ended September 30, 2013
					Parent			Subsidiary			Consolidating
(in thousands)					Issuer			Guarantors			Entries			Total
Net cash flows provided by (used in) operating activities				$	-441,741		$	1,386,385		$	-		$	944,644
Net cash flows used in investing activities					-37,684			-1,434,412			-			-1,472,096
Net cash flows provided by financing activities					479,425			45,169			-			524,594
	Net decrease in cash and cash equivalents				-			-2,858			-			-2,858
	Cash and cash equivalents at beginning of period				-			2,880			-			2,880
	Cash and cash equivalents at end of period			$	-		$	22		$	-		$	22
Condensed Consolidating Statement of Cash Flows
Nine Months Ended September 30, 2012
					Parent			Subsidiary			Subsidiary			Consolidating
(in thousands)					Issuer			Guarantors			Non-Guarantor			Entries		Total
Net cash flows provided by (used in)
	operating activities			$	-1,512,952		$	2,355,751		$	2,837		$	-	$	845,636
Net cash flows used in investing
	activities				-7,485			-1,816,184			-543,738			-		-2,367,407
Net cash flows provided by (used in)
	financing activities				1,520,437			-539,618			540,901			-		1,521,720
	Net decrease in cash and cash
		equivalents			-			-51			-			-		-51
	Cash and cash equivalents at
		beginning of period			-			342			-			-		342
	Cash and cash equivalents at
		end of period		$	-		$	291		$	-		$	-	$	291

Subsequent_events

Subsequent events	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]	'
Subsequent events	'
	Note Q. Subsequent events
	New commodity derivative contracts. After September 30, 2013, the Company entered into the following oil price swaps to hedge additional amounts of the Company's estimated future production:
					First		Second		Third		Fourth
					Quarter		Quarter		Quarter		Quarter		Total
	Oil Swaps: (a)
		2013:00:00
			Volume (Bbl)								150,000		150,000
			Price per Bbl							$	102.55	$	102.55
		2014:00:00
			Volume (Bbl)		153,000		152,000		129,000		91,000		525,000
			Price per Bbl	$	97.78	$	97.78	$	97.71	$	97.53	$	97.72
		2015:00:00
			Volume (Bbl)		94,000		100,000		85,000		96,000		375,000
			Price per Bbl	$	89.84	$	89.84	$	89.83	$	89.84	$	89.84
	(a) The index prices for the oil price swaps are based on the NYMEX – West Texas Intermediate (“WTI”) monthly average futures price.
					First		Second		Third		Fourth
					Quarter		Quarter		Quarter		Quarter		Total
	Oil Swaps: (a)
		2013:00:00
			Volume (Bbl)								150,000		150,000
			Price per Bbl							$	102.55	$	102.55
		2014:00:00
			Volume (Bbl)		153,000		152,000		129,000		91,000		525,000
			Price per Bbl	$	97.78	$	97.78	$	97.71	$	97.53	$	97.72
		2015:00:00
			Volume (Bbl)		94,000		100,000		85,000		96,000		375,000
			Price per Bbl	$	89.84	$	89.84	$	89.83	$	89.84	$	89.84
	(a) The index prices for the oil price swaps are based on the NYMEX – West Texas Intermediate (“WTI”) monthly average futures price.

Supplementary_information

Supplementary information	9 Months Ended
	Sep. 30, 2013
Oil and Gas Exploration and Production Industries Disclosures [Abstract]	'
Supplementary information	'
	Note R. Supplementary information
	Capitalized costs
				September 30,		December 31,
	(in thousands)			2013		2012
	Oil and natural gas properties:
		Proved		$	9,732,454	$	8,402,154
		Unproved			1,119,792		1,053,445
		Less: accumulated depletion			-2,176,041		-1,565,316
			Net capitalized costs for oil and natural gas properties	$	8,676,205	$	7,890,283
	Costs incurred for oil and natural gas producing activities (a)
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Property acquisition costs:
		Proved		$	-	$	690,158	$	2,376	$	855,773
		Unproved			13,991		349,903		58,832		411,110
	Exploration				229,082		223,569		779,026		567,065
	Development				197,696		187,759		593,006		574,541
		Total costs incurred for oil and natural gas properties		$	440,769	$	1,451,389	$	1,433,240	$	2,408,489
	(a)	The costs incurred for oil and natural gas producing activities includes the following amounts of asset retirement obligations:
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
		(in thousands)		2013		2012		2013		2012
		Exploration costs		$	535	$	1,185	$	2,089	$	2,452
		Development costs			1,801		5,019		9,163		8,302
			Total asset retirement obligations	$	2,336	$	6,204	$	11,252	$	10,754
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Property acquisition costs:
		Proved		$	-	$	690,158	$	2,376	$	855,773
		Unproved			13,991		349,903		58,832		411,110
	Exploration				229,082		223,569		779,026		567,065
	Development				197,696		187,759		593,006		574,541
		Total costs incurred for oil and natural gas properties		$	440,769	$	1,451,389	$	1,433,240	$	2,408,489
	(a)	The costs incurred for oil and natural gas producing activities includes the following amounts of asset retirement obligations:
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
		(in thousands)		2013		2012		2013		2012
		Exploration costs		$	535	$	1,185	$	2,089	$	2,452
		Development costs			1,801		5,019		9,163		8,302
			Total asset retirement obligations	$	2,336	$	6,204	$	11,252	$	10,754

Summary_of_significant_account1

Summary of significant accounting policies (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Principles of consolidation	'
	Principles of consolidation. The consolidated financial statements of the Company include the accounts of the Company and its wholly-owned subsidiaries. The Company consolidates the financial statements of these entities. All material intercompany balances and transactions have been eliminated.
Use of estimates in the preparation of financial statements	'
	Use of estimates in the preparation of financial statements.  Preparation of financial statements in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from these estimates. Depletion of oil and natural gas properties is determined using estimates of proved oil and natural gas reserves. There are numerous uncertainties inherent in the estimation of quantities of proved reserves and in the projection of future rates of production and the timing of development expenditures. Similarly, evaluations for impairment of proved and unproved oil and natural gas properties are subject to numerous uncertainties including, among others, estimates of future recoverable reserves and commodity price outlooks. Other significant estimates include, but are not limited to, the asset retirement obligations, fair value of derivative financial instruments, fair value measurements for business combinations and fair value of stock-based compensation.
Interim financial statements	'
	Interim financial statements. The accompanying consolidated financial statements of the Company have not been audited by the Company's independent registered public accounting firm, except that the consolidated balance sheet at December 31, 2012 is derived from audited consolidated financial statements. In the opinion of management, the accompanying consolidated financial statements reflect all adjustments necessary to present fairly the Company's consolidated financial statements. All such adjustments are of a normal, recurring nature. In preparing the accompanying consolidated financial statements, management has made certain estimates and assumptions that affect reported amounts in the consolidated financial statements and disclosures of contingencies. Actual results may differ from those estimates. The results for interim periods are not necessarily indicative of annual results.
	Certain disclosures have been condensed in or omitted from these consolidated financial statements. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company's Annual Report on Form 10-K for the year ended December 31, 2012.
Earnings per share	'Earnings per share. The Company grants non-vested restricted stock awards that meet the definition of a participating security. The Company calculates earnings per share (“EPS”) using the two-class method.
Deferred loan costs.	'
	Deferred loan costs. Deferred loan costs are stated at cost, net of amortization, which is computed using the effective interest and straight-line methods. The Company had deferred loan costs of $76.4 million and $77.6 million, net of accumulated amortization of $45.4 million and $38.8 million, at September 30, 2013 and December 31, 2012, respectively.
	Future amortization expense of deferred loan costs at September 30, 2013 was as follows:
	(in thousands)
	Remaining 2013		$	3,329
	2014			13,503
	2015			13,820
	2016			8,476
	2017			5,994
	2018			6,376
	Thereafter			24,879
		Total	$	76,377
Intangible assets.	'
	Intangible assets. The Company has capitalized certain operating rights acquired in an acquisition. The gross operating rights, which have no residual value, are amortized over the estimated economic life of 25 years. Impairment will be assessed if indicators of potential impairment exist or when there is a material change in the remaining useful economic life. The following table reflects the gross and net intangible assets at September 30, 2013 and December 31, 2012:
				September 30,		December 31,
	(in thousands)			2013		2012
	Gross intangible - operating rights		$	36,557	$	36,557
	Accumulated amortization			-7,577		-6,481
		Net intangible - operating rights	$	28,980	$	30,076
	The following table reflects amortization expense from continuing and discontinued operations for the three and nine months ended September 30, 2013 and 2012:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(in thousands)		2013		2012		2013		2012
	Amortization expense		$	365	$	388	$	1,096	$	1,162
	The following table reflects the estimated aggregate amortization expense for each of the periods presented below at September 30, 2013:
	(in thousands)
	Remaining 2013		$	365
	2014			1,461
	2015			1,461
	2016			1,461
	2017			1,461
	2018			1,461
	Thereafter			21,310
		Total	$	28,980
gas balancing arrangements policy	'
	Oil and natural gas sales and imbalances. Oil and natural gas revenues are recorded at the time of delivery to pipelines for the account of the purchaser or at the time of physical transfer to the purchaser. The Company follows the sales method of accounting for oil and natural gas sales, recognizing revenues based on the Company's share of actual proceeds from the oil and natural gas sold to purchasers. Oil and natural gas imbalances are generated on properties for which two or more owners have the right to take production “in-kind” and, in doing so, take more or less than their respective entitled percentage. Imbalances are tracked by well, but the Company does not record any receivable from or payable to the other owners unless the imbalance has reached a level at which it exceeds the remaining reserves in the respective well. If reserves are insufficient to offset the imbalance and the Company is in an overtake position, a liability is recorded for the amount of shortfall in reserves valued at a contract price or the market price in effect at the time the imbalance is generated. If the Company is in an undertake position, a receivable is recorded for an amount that is reasonably expected to be received, not to exceed the current market value of such imbalance.
Treasury stock	'
	Treasury stock. Treasury stock purchases are recorded at cost. Upon reissuance, the cost of treasury shares held is reduced by the average purchase price per share of the aggregate treasury shares held.
General and administrative expense.	'
	General and administrative expense. The Company receives fees for the operation of jointly-owned oil and natural gas properties and records such reimbursements as reductions of general and administrative expense. Such fees from continuing and discontinued operations totaled approximately $4.2 million and $4.4 million for the three months ended September 30, 2013 and 2012, respectively
Reclassification	'
	Reclassifications. Certain prior period amounts have been reclassified to conform to the 2013 presentation. These reclassifications had no impact on net income, total stockholders' equity or cash flows.
Recent accounting pronouncements	'
	Recent accounting pronouncements. In December 2011, the Financial Accounting Standards Board (the “FASB”) issued amendments that require enhanced disclosure regarding financial instruments and derivative instruments that are either (i) offset in accordance with the current definition of “right of setoff” or the current balance sheet netting for derivative instruments allowed under current U.S. GAAP or (ii) subject to an enforceable master netting arrangement or similar agreement. The Company adopted this update on January 1, 2013, and the update did not have a significant impact on the consolidated financial statements.

Summary_of_significant_account2

Summary of significant accounting policies (Tables)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Schedule Of Expected Amortization Expense Table [Text Block]	'
	(in thousands)
	Remaining 2013		$	3,329
	2014			13,503
	2015			13,820
	2016			8,476
	2017			5,994
	2018			6,376
	Thereafter			24,879
		Total	$	76,377
	(in thousands)
	Remaining 2013		$	365
	2014			1,461
	2015			1,461
	2016			1,461
	2017			1,461
	2018			1,461
	Thereafter			21,310
		Total	$	28,980
Schedule Of Amortization Expense [Table Text Block]	'
				September 30,		December 31,
	(in thousands)			2013		2012
	Gross intangible - operating rights		$	36,557	$	36,557
	Accumulated amortization			-7,577		-6,481
		Net intangible - operating rights	$	28,980	$	30,076
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(in thousands)		2013		2012		2013		2012
	Amortization expense		$	365	$	388	$	1,096	$	1,162

Exploratory_well_costs_Tables

Exploratory well costs (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure Exploratory Well Costs Capitalized Exploratory Well Activity [Abstract]	'
Company's capitalized exploratory well activity	'
	The following table reflects the Company's capitalized exploratory well activity during the three and nine months ended September 30, 2013:
			Three Months Ended			Nine Months Ended
	(in thousands)		30-Sep-13			30-Sep-13
	Beginning capitalized exploratory well costs			$	180,433	$	118,806
		Additions to exploratory well costs pending the determination of proved reserves			262,743		806,327
		Reclassifications due to determination of proved reserves			-270,461		-752,349
		Exploratory well costs charged to expense			-		-69
	Ending capitalized exploratory well costs			$	172,715	$	172,715
Aging of capitalized exploratory well costs based on the date drilling was completed	'
					September 30,		December 31,
	(in thousands)				2013		2012
	Exploratory wells in progress			$	27,176	$	22,837
	Capitalized exploratory well costs that have been capitalized for a period of one year or less				124,464		95,969
	Capitalized exploratory well costs that have been capitalized for a period greater than one year				21,075		-
		Total capitalized exploratory well costs		$	172,715	$	118,806

Acquisitions_and_business_comb1

Acquisitions and business combinations (Tables)	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]	'
Estimated fair value of the acquired assets and liabilities	'
	The following table reflects the fair value of the acquired asset and liabilities with the Three Rivers Acquisition:
	(in thousands)
	Fair value of net assets:
		Proved oil and natural gas properties		$	683,482
		Unproved oil and natural gas properties			359,109
			Total assets acquired		1,042,591
		Current liabilities, including current portion of asset retirement obligations			-2,229
		Asset retirement obligations assumed			-26,002
			Fair value of net assets acquired	$	1,014,360
	Fair value of consideration paid for net assets:
		Cash consideration		$	1,014,360
	The following table reflects the fair value of the acquired assets and liabilities associated with the PDC Acquisition:
	(in thousands)
	Fair value of net assets:
		Current assets		$	2,366
		Proved oil and natural gas properties			159,314
		Unproved oil and natural gas properties			29,687
			Total assets acquired		191,367
		Current liabilities			-123
		Asset retirement obligations assumed			-2,050
			Fair value of net assets acquired	$	189,194
	Fair value of consideration paid for net assets:
		Cash consideration		$	189,194
Business Acquisition, Pro Forma Information [Table Text Block]	'
	The following unaudited pro forma combined condensed financial data for the nine months ended September 30, 2012, were derived from the historical financial statements of the Company giving effect to the Three Rivers Acquisition, as if it had occurred on January 1, 2012. The results of operations since the closing of the Three Rivers Acquisition in July 2012 are included in the Company's results of operations. The pro forma financial data does not include the results of operations for the PDC Acquisition, as the results of operations were deemed not to be material. The unaudited pro forma combined condensed financial data has been included for comparative purposes only and is not necessarily indicative of the results that might have occurred had the Three Rivers Acquisition taken place as of the date indicated and is not intended to be a projection of future results
					Nine Months Ended
					September 30,
	(in thousands, except per share amounts)				2012
					(unaudited)
	Operating revenues				$	1,408,295
	Net income				$	336,712
	Earnings per common share:
		Basic			$	3.27
		Diluted			$	3.24

Asset_retirement_obligations_T

Asset retirement obligations (Tables)	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Asset retirement obligations	'
	The Company's asset retirement obligation transactions during the three and nine months ended September 30, 2013 and 2012 are summarized in the table below:
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Asset retirement obligations, beginning of period		$	96,347	$	68,089	$	86,261	$	59,685
		Liabilities incurred from new wells		1,775		3,053		5,024		6,319
		Liabilities assumed in acquisitions		-		26,986		282		29,113
		Accretion expense for continuing operations		1,574		1,084		4,410		2,826
		Accretion expense for discontinued operations		-		336		-		629
		Disposition of wells		-		-		-303		-66
		Liabilities settled upon plugging and abandoning wells		-897		-272		-2,542		-514
		Revision of estimates		561		3,151		6,228		4,435
	Asset retirement obligations, end of period		$	99,360	$	102,427	$	99,360	$	102,427

Incentive_plans_Tables

Incentive plans (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Number of existing awards and awards available under the Plan	'
	The following table shows the number of existing awards and awards available under the Plan at September 30, 2013:
				Number of
				Common Shares
	Approved and authorized awards			7,500,000
	Restricted stock grants, net of forfeitures			-2,368,907
	Stock option grants, net of forfeitures			-3,463,720
	Performance unit grants (a)			-332,667
	Treasury shares			125,580
		Awards available for future grant		1,460,286
	(a)	This amount represents the 110,889 performance units granted multiplied by the maximum potential payout of 300 percent. The actual payout of shares may be between zero percent and 300 percent of the performance units granted depending on the Company's performance at the end of the performance period.
Summary of the Company's restricted stock awards activity	'
	A summary of the Company's restricted stock award activity for the nine months ended September 30, 2013 is presented below:
					Number of			Grant Date
					Restricted			Fair Value
					Shares			Per Share
	Restricted stock:
		Outstanding at December 31, 2012			1,072,527
			Shares granted		483,440		$	87.69
			Shares cancelled / forfeited		-96,695
			Lapse of restrictions		-220,710
		Outstanding at September 30, 2013			1,238,562
Summarizes information about stock-based compensation for the Company's restricted stock awards activity under the Plan	'
	The following table summarizes information about stock-based compensation for the Company's restricted stock awards activity under the Plan for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended						Nine Months Ended
					September 30,						September 30,
	(in thousands)					2013			2012			2013		2012
	Grant date fair value for awards during the period: (a)
		Employee grants			$	6,881		$	1,180		$	30,934	$	27,306
		Officer and director grants				-			290			12,445		18,521
			Total		$	6,881		$	1,470		$	43,379	$	45,827
	Stock-based compensation expense from restricted stock:
		Employee grants			$	5,116		$	3,854		$	12,511	$	9,617
		Officer and director grants				3,778			4,077			9,701		11,653
			Total		$	8,894		$	7,931		$	22,212	$	21,270
	Income taxes and other information:
		Income tax benefit related to restricted stock			$	3,399		$	3,032		$	8,491	$	8,131
		Deductions in current taxable income related to restricted stock			$	2,302		$	1,043		$	15,847	$	22,581
	(a)		The nine months ended September 30, 2013 includes the effects of $1 million due to modifications of certain stock-based awards.
Summary of the Company's stock option awards activity under the Plan	'
	Stock option awards.  A summary of the Company's stock option award activity under the Plan for the nine months ended September 30, 2013 is presented below:
								Weighted
								Average
					Number of			Exercise
					Options			Price
	Stock options:
		Outstanding at December 31, 2012			429,879		$	20.28
			Options exercised		-139,111		$	16.57
		Outstanding at September 30, 2013			290,768		$	22.05
		Exercisable at end of period			290,768		$	22.05
Summarizes information about the Company's vested and exercisable stock options outstanding	'
	The following table summarizes information about the Company's exercisable stock options outstanding at September 30, 2013:
								Weighted
								Average			Weighted
			Range of					Remaining			Average
			Exercise			Number		Contractual			Exercise				Intrinsic
			Prices			Vested		Life			Price				Value
															(in thousands)
		Vested and exercisable options:
			$8.00			2,005		0.87 years			$	8		$	202
			$12.00			23,788		2.07 years			$	12			2,303
			12.85			15,000		3.88 years			$	12.85			1,439
			$20.00 - $23.00			192,895		4.78 years			$	21.4			16,862
			$28.00 - $37.27			57,080		4.66 years			$	31.34			4,422
						290,768		4.46 years			$	22.05		$	25,228
Summarizes information about stock-based compensation for stock options	'
	The following table summarizes information about stock-based compensation for stock options for the three and nine months ended September 30, 2013 and 2012:
				Three Months Ended							Nine Months Ended
				September 30,							September 30,
	(in thousands)					2013			2012			2013		2012
	Stock-based compensation expense from stock options:
		Employee grants			$	-		$	7		$	2	$	24
		Officer and director grants				-			21			13		140
			Total		$	-		$	28		$	15	$	164
	Income taxes and other information:
		Income tax benefit related to stock options			$	-		$	10		$	5	$	63
		Deductions in current taxable income related to stock options exercised			$	1,797		$	23,332		$	10,317	$	39,420
Summarizes the assumptions to estimate the fair value of performance units granted	'
	The Company used the following assumptions to estimate the fair value of performance unit awards granted during the nine months ended September 30, 2013:
	Risk-free interest rate							0.37%
	Range of volatilities							31.5% - 45.1%
Summary of the Company's performance unit activity	'
	The following table summarizes the performance unit activity for the nine months ended September 30, 2013:
						Number of			Grant Date
						Units (a)			Fair Value
	Performance units:
		Outstanding at December 31, 2012				-
			Units granted			110,889		$	111.4
		Outstanding at September 30, 2013				110,889
	(a)	Reflects the amount of performance units granted. The actual payout of shares will be between zero and 300 percent of the performance units granted depending on the Company's performance at the end of the performance period.
Summarizes information about stock-based compensation for the Company's performance unit awards activity under the Plan	'
	The following table summarizes information about stock-based compensation expense for performance units for the three and nine months ended September 30, 2013:
						Three Months Ended						Nine Months Ended
						September 30,						September 30,
	(in thousands)				2013					2013
	Grant date fair value for awards during the period:
		Officer grants			$	-			$	12,353
	Stock-based compensation expense from performance units:
		Officer grants			$	1,029			$	3,051
	Income taxes:
		Income tax benefit related to performance units			$	394			$	1,167
Future stock-based compensation expense to be recorded for all the stock-based compensation awards that were outstanding	'
	Future stock-based compensation expense. The following table reflects the future stock-based compensation expense to be recorded for all the stock-based compensation awards that were outstanding at September 30, 2013:
					Restricted			Performance
	(in thousands)				Stock			Units			Total
	Remaining 2013			$	9,359		$	1,029		$	10,388
	2014				27,262			4,118			31,380
	2015				14,588			4,154			18,742
	2016				5,245			-			5,245
	2017				548			-			548
		Total		$	57,002		$	9,301		$	66,303

Disclosures_about_fair_value_o1

Disclosures about fair value of financial instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Carrying amounts and fair values of the Company's financial instruments	'
					30-Sep-13						31-Dec-12
					Carrying			Fair			Carrying			Fair
	(in thousands)				Value			Value			Value			Value
		Assets:
			Derivative instruments		$	872		$	872		$	38,711		$	38,711
		Liabilities:
			Derivative instruments		$	95,413		$	95,413		$	13,633		$	13,633
			Credit facility		$	207,600		$	210,666		$	304,000		$	299,679
			8.625% senior notes due 2017		$	-		$	-		$	297,103		$	323,471
			7.0% senior notes due 2021		$	600,000		$	657,000		$	600,000		$	669,000
			6.5% senior notes due 2022		$	600,000		$	643,500		$	600,000		$	660,000
			5.5% senior notes due 2022		$	600,000		$	598,500		$	600,000		$	633,000
			5.5% senior notes due 2023		$	1,581,050		$	1,530,625		$	700,000		$	733,250
Assets and liabilities that are measured at fair value on a recurring basis	'
						Fair Value Measurements Using															Net
						Quoted Prices													Gross		Fair Value
						in Active					Significant						Total		Amounts		Presented
						Markets for					Other			Significant			Fair Value		Offset in the		in the
						Identical					Observable			Unobservable			at		Consolidated		Consolidated
						Assets					Inputs			Inputs			September 30,		Balance		Balance
	(in thousands)					(Level 1)					(Level 2)			(Level 3)			2013		Sheet		Sheet
		Assets
			Current:(a)
				Commodity derivatives			$	-		$	12,880		$	-		$	12,880	$	-12,008	$	872
			Noncurrent:(b)
				Commodity derivatives				-			4,600			-			4,600		-4,600		-
		Liabilities
			Current:(a)
				Commodity derivatives				-			-83,372			-			-83,372		12,008		-71,364
			Noncurrent:(b)
				Commodity derivatives				-			-28,649			-			-28,649		4,600		-24,049
		Net derivative instruments					$	-		$	-94,541		$	-		$	-94,541	$	-	$	-94,541
						Fair Value Measurements Using															Net
						Quoted Prices													Gross		Fair Value
						in Active					Significant						Total		Amounts		Presented
						Markets for					Other			Significant			Fair Value		Offset in the		in the
						Identical					Observable			Unobservable			at		Consolidated		Consolidated
						Assets					Inputs			Inputs			December 31,		Balance		Balance
	(in thousands)					(Level 1)					(Level 2)			(Level 3)			2012		Sheet		Sheet
		Assets
			Current:(a)
				Commodity derivatives			$	-		$	56,471		$	-		$	56,471	$	-20,529	$	35,942
			Noncurrent:(b)
				Commodity derivatives				-			12,108			-			12,108		-9,339		2,769
		Liabilities
			Current:(a)
				Commodity derivatives				-			-22,113			-			-22,113		20,529		-1,584
			Noncurrent:(b)
				Commodity derivatives				-			-21,388			-			-21,388		9,339		-12,049
		Net derivative instruments					$	-		$	25,078		$	-		$	25,078	$	-	$	25,078
Carrying amounts, estimated fair values and impairment expense of long-lived assets	'
							Estimated
				Carrying			Fair Value			Impairment
	(in thousands)			Amount			(Level 3)			Expense
	Nine Months Ended September 30, 2013		$	84,140		$	18,765		$	65,375

Derivative_financial_instrumen1

Derivative financial instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Summarizes the gains and losses reported in earnings related to the commodity and interest rate derivative instruments	'
				Three Months Ended						Nine Months Ended
				September 30,						September 30,
	(in thousands)				2013			2012			2013			2012
	Gain (loss) on derivatives not designated as hedges:
		Oil derivatives		$	-169,049		$	-135,401		$	-172,698		$	109,386
		Natural gas derivatives			439			-14			15,395			156
			Total gain (loss) on derivatives not designated as hedges	$	-168,610		$	-135,415		$	-157,303		$	109,542
	The following table represents the Company's cash receipts from (payments on) derivatives not designated as hedges for the three and nine months ended September 30, 2013 and 2012:
				Three Months Ended						Nine Months Ended
				September 30,						September 30,
	(in thousands)				2013			2012			2013			2012
	Cash receipts from (payments on) derivatives not designated as hedges:
		Oil derivatives		$	-49,864		$	15,859		$	-42,528		$	-8,374
		Natural gas derivatives			4,589			280			4,844			889
			Total cash receipts from (payments on) derivatives not designated as hedges	$	-45,275		$	16,139		$	-37,684		$	-7,485
Company's outstanding derivative contracts	'
					First		Second		Third		Fourth
					Quarter		Quarter		Quarter		Quarter		Total
	Oil Swaps: (a)
		2013:00:00
			Volume (Bbl)								4,614,000		4,614,000
			Price per Bbl							$	95.87	$	95.87
		2014:00:00
			Volume (Bbl)		4,277,000		3,848,000		3,560,000		3,355,000		15,040,000
			Price per Bbl	$	93.31	$	92.18	$	90.61	$	90.54	$	91.76
		2015:00:00
			Volume (Bbl)		3,154,000		2,984,000		2,858,000		2,721,000		11,717,000
			Price per Bbl	$	87.24	$	86.36	$	86.66	$	86.58	$	86.72
		2016:00:00
			Volume (Bbl)		108,000		108,000		108,000		105,000		429,000
			Price per Bbl	$	88.32	$	88.32	$	88.32	$	88.28	$	88.31
		2017:00:00
			Volume (Bbl)		84,000		84,000		-		-		168,000
			Price per Bbl	$	87	$	87	$	-	$	-	$	87
	Oil Basis Swaps: (b)
		2013:00:00
			Volume (Bbl)								3,404,000		3,404,000
			Price per Bbl							$	-1.12	$	-1.12
		2014:00:00
			Volume (Bbl)		2,790,000		2,821,000		1,932,000		1,932,000		9,475,000
			Price per Bbl	$	-0.46	$	-0.46	$	-0.45	$	-0.45	$	-0.46
	Natural Gas Swaps: (c)
		2013:00:00
			Volume (MMBtu)								6,992,000		6,992,000
			Price per MMBtu							$	4.25	$	4.25
	Natural Gas Collars: (d)
		2014:00:00
			Volume (MMBtu)		5,400,000		5,460,000		5,520,000		5,520,000		21,900,000
			Ceiling price per MMBtu	$	4.4	$	4.4	$	4.4	$	4.4	$	4.4
			Floor price per MMBtu	$	3.85	$	3.85	$	3.85	$	3.85	$	3.85
	Natural Gas Basis Swaps: (e)
		2013:00:00
			Volume (MMBtu)								6,440,000		6,440,000
			Price per MMBtu							$	-0.15	$	-0.15
	(a) The index prices for the oil price swaps are based on the NYMEX – West Texas Intermediate (“WTI”) monthly average futures price.
	(b) The basis differential price is between Midland – WTI and Cushing – WTI.
	(c) The index prices for the natural gas price swaps are based on the NYMEX – Henry Hub last trading day futures price.
	(d) The index prices for the natural gas collars are based on the El Paso Permian delivery point.
	(e) The basis differential price is between the El Paso Permian delivery point and NYMEX – Henry Hub delivery point.

Debt_Tables

Debt (Tables)	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Company's debt	'
						September 30,			December 31,
	(in thousands)					2013			2012
	Credit facility				$	207,600		$	304,000
	8.625% unsecured senior notes due 2017					-			300,000
	7.0% unsecured senior notes due 2021					600,000			600,000
	6.5% unsecured senior notes due 2022					600,000			600,000
	5.5% unsecured senior notes due 2022					600,000			600,000
	5.5% unsecured senior notes due 2023					1,550,000			700,000
	Unamortized original issue premium (discount), net					31,050			-2,897
		Less: current portion				-			-
			Total long-term debt		$	3,588,650		$	3,101,103
Future interest expense from the 2017 Senior Notes original issue discount	'
	Future benefit to interest expense from original issue premium at September 30, 2013 was as follows:
	(in thousands)
	Remaining 2013			$		629
	2014					2,602
	2015					2,747
	2016					2,900
	2017					3,062
	2018					3,233
	Thereafter					15,877
		Total		$		31,050
Principal maturities of debt	'
	Principal maturities of debt. Principal maturities of long-term debt outstanding at September 30, 2013 were as follows:
	(in thousands)
	Remaining 2013			$		-
	2014					-
	2015					-
	2016					207,600
	2017					-
	2018					-
	Thereafter					3,350,000
		Total		$		3,557,600
Interest expense	'
	Interest expense. The following amounts have been incurred and charged to interest expense for the three and nine months ended September 30, 2013 and 2012:
							Three Months Ended					Nine Months Ended
							September 30,					September 30,
	(in thousands)							2013			2012		2013		2012
	Cash payments for interest						$	43,868		$	48,203	$	145,980	$	115,731
	Amortization of original issue discount (premium)							-620			117		-619		342
	Amortization of deferred loan origination costs							3,311			3,114		9,844		8,724
	Net changes in accruals							9,436			-97		6,975		4,276
		Total interest expense					$	55,995		$	51,337	$	162,180	$	129,073

Commitments_and_contingencies_

Commitments and contingencies (Tables)	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Summary of the Company's future drilling commitments	'
	The following table summarizes the Company's future drilling commitments at September 30, 2013:
			Payments Due By Period
							Less than		3-Jan		5-Mar		More than
	(in thousands)			Total			1 year		years		years		5 years
	Contractual drilling commitments		$	8,084		$	8,084	$	-	$	-	$	-
Future minimum lease commitments under non-cancellable operating leases	'
	Future minimum lease commitments under non-cancellable operating leases at September 30, 2013 were as follows:
	(in thousands)
	Remaining 2013			$	1,508
	2014				5,372
	2015				4,146
	2016				2,778
	2017				750
	2018				441
	Thereafter				1,247
		Total		$	16,242

Income_taxes_Tables

Income taxes (Tables)	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
The Company's income tax provision	'
	Income tax provision. The Company's income tax provision (benefit) and amounts separately allocated were attributable to the following items for the three and nine months ended September 30, 2013 and 2012:
							Three Months Ended						Nine Months Ended
							September 30,						September 30,
	(in thousands)							2013			2012			2013			2012
	Income (loss) from continuing operations						$	21,695		$	-995		$	86,023		$	204,327
	Income from discontinued operations							-			5,150			7,518			16,508
	Changes in stockholders' equity:
		Excess tax benefits related to stock-based compensation						-5,081			-8,129			-9,244			-18,522
							$	16,614		$	-3,974		$	84,297		$	202,313
Company's income tax provision attributable to income from continuing operations	'
	The Company's income tax provision (benefit) attributable to income from continuing operations consisted of the following for the three and nine months ended September 30, 2013 and 2012:
							Three Months Ended						Nine Months Ended
							September 30,						September 30,
	(in thousands)							2013			2012			2013			2012
	Current:
		U.S. federal					$	-3,661		$	-3,259		$	8,427		$	-1,155
		U.S. state and local						-106			555			1,788			2,375
			Total current income tax provision (benefit)					-3,767			-2,704			10,215			1,220
	Deferred:
		U.S. federal						23,652			2,240			67,529			178,766
		U.S. state and local						1,810			-531			8,279			24,341
			Total deferred income tax provision					25,462			1,709			75,808			203,107
				Total income tax provision (benefit) attributable to income from
					continuing operations		$	21,695		$	-995		$	86,023		$	204,327
reconciliation between the income tax expense computed by multiplying pretax income from continuing operations	'
	The reconciliation between the income tax expense (benefit) computed by multiplying pretax income (loss) from continuing operations by the United States federal statutory rate and the reported amounts of income tax expense (benefit) from continuing operations is as follows:
							Three Months Ended						Nine Months Ended
							September 30,						September 30,
	(in thousands)							2013			2012			2013			2012
	Income (loss) at U.S. federal statutory rate						$	18,241		$	-1,458		$	76,705		$	185,979
	State income taxes (net of federal tax effect)							1,726			-159			7,161			17,245
	Revision of previous tax estimates							1,273			219			1,273			219
	Statutory depletion							58			-91			-21			-207
	Nondeductible expense & other							397			494			905			1,091
		Income tax expense (benefit)					$	21,695		$	-995		$	86,023		$	204,327
	Effective tax rate							41.60%			23.90%			39.30%			38.50%
Company's income tax provision attributable to income from discontinued operations	'
	The Company's income tax provision attributable to income from discontinued operations consisted of the following for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended						Nine Months Ended
					September 30,						September 30,
	(in thousands)				2013			2012			2013			2012
	Current:
		U.S. federal			$	-		$	4,589		$	144		$	14,729
		U.S. state and local				-			25			25			82
			Total current income tax provision			-			4,614			169			14,811
	Deferred:
		U.S. federal				-			-107			6,397			-366
		U.S. state and local				-			643			952			2,063
			Total deferred income tax provision			-			536			7,349			1,697
				Total income tax provision attributable to
				income from discontinued operations	$	-		$	5,150		$	7,518		$	16,508

Related_party_transactions_Tab

Related party transactions (Tables)	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]	'
Summary of charges incurred with and payments made to the Company's related parties and reported in the consolidated statements of operations, as well as outstanding payables included in the consolidated balance sheets	'
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Royalties paid to a partnership in which a director has an ownership interest (a)		$	2,010	$	525	$	4,694	$	1,820
	Royalties paid to a director and certain officers of the Company (b)		$	12	$	-	$	33	$	-
	Amounts paid under consulting agreement with Steven L. Beal (c)		$	745	$	60	$	865	$	180
							September 30,		December 31,
	(in thousands)						2013		2012
	Amounts included in accounts payable - related parties:
		Royalty interests of a director of the Company (a)					$	0	$	185
	Royalties paid on certain properties to a partnership of which a director is the general partner and owns a 3.5 percent partnership interest.
	Payments made to a director and certain officers who directly own overriding royalty interests in properties owned by the Company.
	On June 30, 2009, Steven L. Beal, the Company's then-president and chief operating officer, retired from such positions. On June 9, 2009, the Company entered into a consulting agreement (the “Consulting Agreement”) with Mr. Beal, under which Mr. Beal began serving as a consultant to the Company on July 1, 2009. During the term of the consulting relationship, Mr. Beal received a consulting fee of $20,000 per month and a monthly reimbursement for his medical and dental coverage costs. In August 2013, the Company and Mr. Beal mutually terminated the Consulting Agreement in exchange for the payment to Mr. Beal of $720,000, which termination and payment were approved by the disinterested members of the Company's Board of Directors.

Discontinued_operations_Tables

Discontinued operations (Tables)	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]	'
Components of the Company's discontinued operations	'
	The following table represents the components of the Company's discontinued operations for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended				Nine Months Ended
					September 30,				September 30,
	(in thousands)				2013		2012		2013	2012
	Operating revenues:
		Oil sales		$	-	$	26,616	$	-	$	82,518
		Natural gas sales			-		5,588		-		13,342
			Total operating revenues		-		32,204		-		95,860
	Operating costs and expenses:
		Oil and natural gas production			-		8,702		-		24,864
		Depreciation, depletion and amortization (a)			-		9,476		-		26,265
		Accretion of discount on asset retirement obligations (a)			-		336		-		629
		General and administrative (b)			-		-619		-		-1,766
			Total operating costs and expenses		-		17,895		-		49,992
	Income from operations				-		14,309		-		45,868
	Other income (expense):
		Gain on disposition of assets, net (a)			-		-		19,599		-
	Income from discontinued operations before income taxes				-		14,309		19,599		45,868
	Income tax expense:
		Current			-		-4,614		-169		-14,811
		Deferred (a)			-		-536		-7,349		-1,697
	Income from discontinued operations, net of tax			$	-	$	9,159	$	12,081	$	29,360
	(a)		Represents the significant non-cash components of discontinued operations.
	(b)		Represents the fees received from third-parties for operating oil and natural gas properties that were sold. The Company reflects these fees as a reduction of general and administrative expenses.

Net_income_per_share_Tables

Net income per share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]	'
Reconciliation of earnings attributable to common shares, basic and diluted	'
						Three Months Ended								Nine Months Ended
						30-Sep-13								30-Sep-13
					Continuing			Discontinued					Continuing		Discontinued
	(in thousands, except per share amounts)				Operations			Operations			Total		Operations		Operations		Total
	Income as reported				$	30,421		$	-		$	30,421	$	133,133	$	12,081	$	145,214
	Participating basic earnings					-357			-			-357		-1,421		-129		-1,550
		Basic income attributable to common
			stockholders			30,064			-			30,064		131,712		11,952		143,664
	Reallocation of participating earnings					-			-			-		2		-		2
		Diluted income attributable to common
			stockholders		$	30,064		$	-		$	30,064	$	131,714	$	11,952	$	143,666
	Income per common share:
		Basic			$	0.29		$	-		$	0.29	$	1.27	$	0.12	$	1.39
		Diluted			$	0.29		$	-		$	0.29	$	1.27	$	0.11	$	1.38
						Three Months Ended								Nine Months Ended
						30-Sep-12								30-Sep-12
					Continuing			Discontinued					Continuing		Discontinued
	(in thousands, except per share amounts)				Operations			Operations			Total		Operations		Operations		Total
	Income (loss) as reported				$	-3,171		$	9,159		$	5,988	$	327,042	$	29,360	$	356,402
	Participating basic earnings					-			-			-		-		-		-
		Basic income (loss) attributable to
			common stockholders			-3,171			9,159			5,988		327,042		29,360		356,402
	Reallocation of participating earnings					-			-			-		-		-		-
		Diluted income (loss) attributable to
			common stockholders		$	-3,171		$	9,159		$	5,988	$	327,042	$	29,360	$	356,402
	Income (loss) per common share:
		Basic			$	-0.03		$	0.09		$	0.06	$	3.17	$	0.29	$	3.46
		Diluted			$	-0.03		$	0.09		$	0.06	$	3.15	$	0.28	$	3.43
reconciliation of the basic weighted average common shares outstanding to diluted weighted average common shares outstanding	'
	The following table is a reconciliation of the basic weighted average common shares outstanding to diluted weighted average common shares outstanding for the three and nine months ended September 30, 2013 and 2012:
					Three Months Ended				Nine Months Ended
					September 30,				September 30,
	(in thousands)				2013		2012		2013		2012
	Weighted average common shares outstanding:
		Basic			103,801		103,292		103,709		103,088
			Dilutive common stock options		157		323		173		399
			Dilutive restricted stock		-		425		-		411
			Dilutive performance units		-		-		-		-
		Diluted			103,958		104,040		103,882		103,898
summary of the common stock options and restricted stock which were not included in the computation of diluted net income per share	'
	The following table is a summary of the common stock options, restricted stock and performance units which were not included in the computation of diluted net income per share, as inclusion would be antidilutive:
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Number of antidilutive common shares:
		Antidilutive common stock options		-		-		-		-
		Antidilutive restricted stock		2		31		7		126
		Antidilutive performance units		111		-		111		-

Other_current_liabilities_Tabl

Other current liabilities (Tables)	9 Months Ended
	Sep. 30, 2013
Other Liabilities Disclosure [Abstract]	'
components of the Company's other current liabilities	'
	The following table provides the components of the Company's other current liabilities at September 30, 2013 and December 31, 2012:
					September 30,		December 31,
	(in thousands)				2013		2012
	Other current liabilities:
		Accrued production costs		$	53,642	$	52,825
		Payroll related matters			21,360		16,365
		Accrued interest			79,460		64,304
		Settlements due on derivatives not designated as hedges			17,304		-
		Acquisition and divestiture settlements			-		18,100
		Income taxes payable			425		2,141
		Asset retirement obligations			2,674		3,308
		Other			3,862		3,297
			Other current liabilities	$	178,727	$	160,340

Subsidiary_guarantors_Tables

Subsidiary guarantors (Tables)	9 Months Ended
	Sep. 30, 2013
Guarantees [Abstract]	'
Condensed Consolidating Balance Sheet	'
	Condensed Consolidating Balance Sheet
	30-Sep-13
					Parent			Subsidiary			Consolidating
	(in thousands)				Issuer			Guarantors			Entries			Total
	ASSETS
	Accounts receivable - related parties			$	6,158,999		$	1,279,039		$	-7,438,038		$	-
	Other current assets				36,298			571,414			-			607,712
	Oil and natural gas properties, net				-			8,676,205			-			8,676,205
	Property and equipment, net				-			111,705			-			111,705
	Investment in subsidiaries				3,735,429			-			-3,735,429			-
	Other long-term assets				76,376			58,703			-			135,079
		Total assets		$	10,007,102		$	10,697,066		$	-11,173,467		$	9,530,701
	LIABILITIES AND EQUITY
	Accounts payable - related parties			$	1,279,039		$	6,158,999		$	-7,438,038		$	-
	Other current liabilities				168,402			705,882			-			874,284
	Other long-term liabilities				1,326,298			96,756			-			1,423,054
	Long-term debt				3,588,650			-			-			3,588,650
	Equity				3,644,713			3,735,429			-3,735,429			3,644,713
		Total liabilities and equity		$	10,007,102		$	10,697,066		$	-11,173,467		$	9,530,701
	Condensed Consolidating Balance Sheet
	31-Dec-12
					Parent			Subsidiary			Consolidating
	(in thousands)				Issuer			Guarantors			Entries			Total
	ASSETS
	Accounts receivable - related parties			$	5,839,995		$	2,416,697		$	-8,256,692		$	-
	Other current assets				46,737			412,145			-			458,882
	Oil and natural gas properties, net				-			7,890,283			-			7,890,283
	Property and equipment, net				-			103,141			-			103,141
	Investment in subsidiaries				3,146,918			-			-3,146,918			-
	Other long-term assets				80,378			56,753			-			137,131
		Total assets		$	9,114,028		$	10,879,019		$	-11,403,610		$	8,589,437
	LIABILITIES AND EQUITY
	Accounts payable - related parties			$	1,271,563		$	6,985,314		$	-8,256,692		$	185
	Other current liabilities				76,496			663,405			-			739,901
	Other long-term liabilities				1,198,670			83,382			-			1,282,052
	Long-term debt				3,101,103			-			-			3,101,103
	Equity				3,466,196			3,146,918			-3,146,918			3,466,196
		Total liabilities and equity		$	9,114,028		$	10,879,019		$	-11,403,610		$	8,589,437
Condensed Consolidating Statement of Operations	'
	Condensed Consolidating Statement of Operations
	Three Months Ended September 30, 2013
					Parent			Subsidiary			Consolidating
	(in thousands)				Issuer			Guarantors			Entries			Total
	Total operating revenues			$	-		$	652,920		$	-		$	652,920
	Total operating costs and expenses				-169,935			-372,933			-			-542,868
		Income (loss) from continuing operations			-169,935			279,987			-			110,052
	Interest expense				-55,995			-			-			-55,995
	Other, net				278,046			-1,996			-277,991			-1,941
		Income from continuing operations before income taxes			52,116			277,991			-277,991			52,116
	Income tax expense				-21,695			-			-			-21,695
		Net income		$	30,421		$	277,991		$	-277,991		$	30,421
	Condensed Consolidating Statement of Operations
	Three Months Ended September 30, 2012
						Parent			Subsidiary			Subsidiary			Consolidating
	(in thousands)					Issuer			Guarantors			Non-Guarantor			Entries		Total
	Total operating revenues				$	-		$	458,001		$	7,342		$	-	$	465,343
	Total operating costs and expenses					-135,637			-273,701			-5,720			-		-415,058
		Income (loss) from continuing operations				-135,637			184,300			1,622			-		50,285
	Interest expense					-51,337			-			-			-		-51,337
	Other, net					197,117			2,309			-6,043			-196,497		-3,114
		Income (loss) from continuing
			operations before income taxes			10,143			186,609			-4,421			-196,497		-4,166
	Income tax benefit					995			-			-			-		995
		Income (loss) from continuing operations				11,138			186,609			-4,421			-196,497		-3,171
	Income (loss) from discontinued
		operations, net of tax				-5,150			14,309			-			-		9,159
		Net income (loss)			$	5,988		$	200,918		$	-4,421		$	-196,497	$	5,988
	Condensed Consolidating Statement of Operations
	Nine Months Ended September 30, 2013
					Parent			Subsidiary			Consolidating
	(in thousands)				Issuer			Guarantors			Entries			Total
	Total operating revenues			$	-		$	1,687,833		$	-		$	1,687,833
	Total operating costs and expenses				-159,017			-1,117,058			-			-1,276,075
		Income (loss) from continuing operations			-159,017			570,775			-			411,758
	Interest expense				-162,180			-			-			-162,180
	Loss on extinguishment of debt				-28,616			-			-			-28,616
	Other, net				588,568			-1,863			-588,511			-1,806
		Income from continuing operations before income taxes			238,755			568,912			-588,511			219,156
	Income tax expense				-86,023			-			-			-86,023
		Income from continuing operations			152,732			568,912			-588,511			133,133
	Income (loss) from discontinued operations, net of tax				-7,518			19,599			-			12,081
		Net income		$	145,214		$	588,511		$	-588,511		$	145,214
	Condensed Consolidating Statement of Operations
	Nine Months Ended September 30, 2012
						Parent			Subsidiary			Subsidiary			Consolidating
	(in thousands)					Issuer			Guarantors			Non-Guarantor			Entries		Total
	Total operating revenues				$	-		$	1,334,946		$	7,342		$	-	$	1,342,288
	Total operating costs and expenses					108,776			-779,985			-5,720			-		-676,929
		Income from continuing operations				108,776			554,961			1,622			-		665,359
	Interest expense					-129,073			-			-			-		-129,073
	Other, net					597,534			522			-6,043			-596,930		-4,917
		Income (loss) from continuing
			operations before income taxes			577,237			555,483			-4,421			-596,930		531,369
	Income tax expense					-204,327			-			-			-		-204,327
		Income (loss) from continuing operations				372,910			555,483			-4,421			-596,930		327,042
	Income (loss) from discontinued
		operations, net of tax				-16,508			45,868			-			-		29,360
		Net income (loss)			$	356,402		$	601,351		$	-4,421		$	-596,930	$	356,402
Condensed Consolidating Statement of Cash Flows	'
	Condensed Consolidating Statement of Cash Flows
	Nine Months Ended September 30, 2013
						Parent			Subsidiary			Consolidating
	(in thousands)					Issuer			Guarantors			Entries			Total
	Net cash flows provided by (used in) operating activities				$	-441,741		$	1,386,385		$	-		$	944,644
	Net cash flows used in investing activities					-37,684			-1,434,412			-			-1,472,096
	Net cash flows provided by financing activities					479,425			45,169			-			524,594
		Net decrease in cash and cash equivalents				-			-2,858			-			-2,858
		Cash and cash equivalents at beginning of period				-			2,880			-			2,880
		Cash and cash equivalents at end of period			$	-		$	22		$	-		$	22
	Condensed Consolidating Statement of Cash Flows
	Nine Months Ended September 30, 2012
						Parent			Subsidiary			Subsidiary			Consolidating
	(in thousands)					Issuer			Guarantors			Non-Guarantor			Entries		Total
	Net cash flows provided by (used in)
		operating activities			$	-1,512,952		$	2,355,751		$	2,837		$	-	$	845,636
	Net cash flows used in investing
		activities				-7,485			-1,816,184			-543,738			-		-2,367,407
	Net cash flows provided by (used in)
		financing activities				1,520,437			-539,618			540,901			-		1,521,720
		Net decrease in cash and cash
			equivalents			-			-51			-			-		-51
		Cash and cash equivalents at
			beginning of period			-			342			-			-		342
		Cash and cash equivalents at
			end of period		$	-		$	291		$	-		$	-	$	291

Subsequent_events_Tables

Subsequent events (Tables)	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]	'
New commodity derivative contracts	'
	New commodity derivative contracts. After September 30, 2013, the Company entered into the following oil price swaps to hedge additional amounts of the Company's estimated future production:
					First		Second		Third		Fourth
					Quarter		Quarter		Quarter		Quarter		Total
	Oil Swaps: (a)
		2013:00:00
			Volume (Bbl)								150,000		150,000
			Price per Bbl							$	102.55	$	102.55
		2014:00:00
			Volume (Bbl)		153,000		152,000		129,000		91,000		525,000
			Price per Bbl	$	97.78	$	97.78	$	97.71	$	97.53	$	97.72
		2015:00:00
			Volume (Bbl)		94,000		100,000		85,000		96,000		375,000
			Price per Bbl	$	89.84	$	89.84	$	89.83	$	89.84	$	89.84
	(a) The index prices for the oil price swaps are based on the NYMEX – West Texas Intermediate (“WTI”) monthly average futures price.
					First		Second		Third		Fourth
					Quarter		Quarter		Quarter		Quarter		Total
	Oil Swaps: (a)
		2013:00:00
			Volume (Bbl)								150,000		150,000
			Price per Bbl							$	102.55	$	102.55
		2014:00:00
			Volume (Bbl)		153,000		152,000		129,000		91,000		525,000
			Price per Bbl	$	97.78	$	97.78	$	97.71	$	97.53	$	97.72
		2015:00:00
			Volume (Bbl)		94,000		100,000		85,000		96,000		375,000
			Price per Bbl	$	89.84	$	89.84	$	89.83	$	89.84	$	89.84
	(a) The index prices for the oil price swaps are based on the NYMEX – West Texas Intermediate (“WTI”) monthly average futures price.

Supplementary_information_Tabl

Supplementary information (Tables)	9 Months Ended
	Sep. 30, 2013
Oil and Gas Exploration and Production Industries Disclosures [Abstract]	'
Capitalized costs	'
				September 30,		December 31,
	(in thousands)			2013		2012
	Oil and natural gas properties:
		Proved		$	9,732,454	$	8,402,154
		Unproved			1,119,792		1,053,445
		Less: accumulated depletion			-2,176,041		-1,565,316
			Net capitalized costs for oil and natural gas properties	$	8,676,205	$	7,890,283
costs incurred for oil and natural gas producing activities	'
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
	(in thousands)			2013		2012		2013		2012
	Property acquisition costs:
		Proved		$	-	$	690,158	$	2,376	$	855,773
		Unproved			13,991		349,903		58,832		411,110
	Exploration				229,082		223,569		779,026		567,065
	Development				197,696		187,759		593,006		574,541
		Total costs incurred for oil and natural gas properties		$	440,769	$	1,451,389	$	1,433,240	$	2,408,489
	(a)	The costs incurred for oil and natural gas producing activities includes the following amounts of asset retirement obligations:
				Three Months Ended				Nine Months Ended
				September 30,				September 30,
		(in thousands)		2013		2012		2013		2012
		Exploration costs		$	535	$	1,185	$	2,089	$	2,452
		Development costs			1,801		5,019		9,163		8,302
			Total asset retirement obligations	$	2,336	$	6,204	$	11,252	$	10,754

Recovered_Sheet1

Summary Of Significant Accounting Policies (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Disclosure Summary Of Significant Accounting Policies Narrative [Abstract]	'	'	'	'	'
Deferred loan costs	$76,377,000	'	$76,377,000	'	$77,609,000
Accumulated amortization	'	'	45,400,000	'	38,800,000
Estimated economic life of gross operating rights in years	'25 years	'	'	'	'
Fees related to operation of jointly owned oil and natural gas properties	$4,200,000	$4,400,000	$13,500,000	$12,500,000	'

Recovered_Sheet2

Summary Of Significant Accounting Policies (Future Amortization Expense Of Deferred Loan Costs) (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Disclosure Summary Of Significant Accounting Policies Future Amortization Expense Of Deferred Loan Costs [Abstract]	'
Remaining 2013	$3,329
2014	13,503
2015	13,820
2016	8,476
2017	5,994
2018	6,376
Thereafter	24,879
Total	$76,377

Recovered_Sheet3

Summary Of Significant Accounting Policies (Gross And Net Intangible Assets) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Disclosure Summary Of Significant Accounting Policies Gross And Net Intangible Assets [Abstract]	'	'
Gross intangible - operating rights	$36,557	$36,557
Accumulated amortization	-7,577	-6,481
Net intangible - operating rights	$28,980	$30,076

Summary_Of_Significant_Account3

Summary Of Significant Accounting Policies (Amortization Expense) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Summary Of Significant Accounting Policies Amortization Expense [Abstract]	'	'	'	'
Amortization expense	$365	$388	$1,096	$1,162

Summary_Of_Significant_Account4

Summary Of Significant Accounting Policies (Estimated Future Aggregate Amortization Expense) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Disclosure Summary Of Significant Accounting Policies Estimated Future Aggregate Amortization Expense [Abstract]	'	'
Remaining 2013	$365	'
2014	1,461	'
2015	1,461	'
2016	1,461	'
2017	1,461	'
2018	1,461	'
Thereafter	21,310	'
Total	$28,980	$30,076

Exploratory_Well_Costs_Capital

Exploratory Well Costs (Capitalized Exploratory Well Activity) (Detail) (USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013
Disclosure Exploratory Well Costs Capitalized Exploratory Well Activity [Abstract]	'	'
Beginning capitalized exploratory well costs	$180,433	$118,806
Additions to exploratory well costs pending the determination of proved reserves	262,743	806,327
Reclassifications due to determination of proved reserves	-270,461	-752,349
Exploratory well costs charged to expense	0	-69
Ending capitalized exploratory well costs	$172,715	$172,715

Exploratory_Well_Costs_Aging_O

Exploratory Well Costs (Aging Of Capitalized Exploratory Well Costs Based On The Date Of Drilling) (Detail) (USD $)	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Disclosure Exploratory Well Costs Aging Of Capitalized Exploratory Well Costs Based On The Date Of Drilling [Abstract]	'	'	'
Exploratory wells in progress	$27,176	'	$22,837
Capitalized exploratory well costs that have been capitalized for a period of one year or less	124,464	'	95,969
Capitalized exploratory well costs that have been capitalized for a period greater than one year	21,075	'	0
Total capitalized exploratory well costs	$172,715	$180,433	$118,806

Exploratory_Well_Costs_Narrati

Exploratory Well Costs (Narrative) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Number
Oil And Gas In Process Activities [Line Items]	'	'
Gross exploratory wells	75	'
Capitalized exploratory well costs that have been capitalized for a period greater than one year	$21,075	$0
Delaware Basin Area [Member]	'	'
Oil And Gas In Process Activities [Line Items]	'	'
Gross exploratory wells	20	'
New Mexico Shelf Area [Member]	'	'
Oil And Gas In Process Activities [Line Items]	'	'
Gross exploratory wells	27	'
Texas Permian Area [Member]	'	'
Oil And Gas In Process Activities [Line Items]	'	'
Gross exploratory wells	28	'
Northern Midland Basin Project [Member]	'	'
Oil And Gas In Process Activities [Line Items]	'	'
Capitalized exploratory well costs that have been capitalized for a period greater than one year	6,300	'
Southern Delaware Basin Project [Member]	'	'
Oil And Gas In Process Activities [Line Items]	'	'
Capitalized exploratory well costs that have been capitalized for a period greater than one year	$9,500	'

Recovered_Sheet4

Acquisitions And Business Combinations (Narrative) (Detail) (USD $)	Sep. 30, 2013	Jul. 31, 2012	Sep. 30, 2013	Feb. 29, 2012
In Thousands, unless otherwise specified	Three Rivers Operating Company Acquisition [Member]	Three Rivers Operating Company Acquisition [Member]	Petroleum Development Corporation Acquisition [Member]	Petroleum Development Corporation Acquisition [Member]
Business Acquisition [Line Items]	'	'	'	'
Cash consideration	$1,014,360	$1,000,000	$189,194	$189,200

Recovered_Sheet5

Acquisitions And Business Combinations (Fair Value of Net Assets) (Detail) (USD $)	Sep. 30, 2013	Feb. 29, 2012	Sep. 30, 2013	Jul. 31, 2012
In Thousands, unless otherwise specified	PDC Acquisition [Member]	PDC Acquisition [Member]	Three Rivers Acquisition [Member]	Three Rivers Acquisition [Member]
Business Acquisition [Line Items]	'	'	'	'
Current assets	$2,366	'	'	'
Proved Oil and gas properties	159,314	'	683,482	'
Unproved oil and gas properties	29,687	'	359,109	'
Total assets acquired	191,367	'	1,042,591	'
Current liabilities	-123	'	-2,229	'
Assets Retirement obligation and other liabilities assumed	-2,050	'	-26,002	'
Fair value of net assets acquired	189,194	'	1,014,360	'
Cash consideration	$189,194	$189,200	$1,014,360	$1,000,000

Acquisitions_And_Business_Comb2

Acquisitions And Business Combinations (Fair Value of consideration paid for net assets) (Detail) (USD $)	Sep. 30, 2013	Feb. 29, 2012	Sep. 30, 2013	Jul. 31, 2012
In Thousands, unless otherwise specified	PDC Acquisition [Member]	PDC Acquisition [Member]	Three Rivers Operating Company Acquisition [Member]	Three Rivers Operating Company Acquisition [Member]
Business Acquisition [Line Items]	'	'	'	'
Cash consideration	$189,194	$189,200	$1,014,360	$1,000,000

Acquisitions_And_Business_Comb3

Acquisitions And Business Combinations (Pro Forma Data) (Detail) (USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2012
Business Acquisition, Pro Forma Information [Abstract]	'
Business Acquisition, Pro Forma Revenue	$1,408,295
Business Acquisition, Pro Forma Net Income (Loss)	$336,712
Business Acquisition, Pro Forma Earnings Per Share, Basic	$3.27
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$3.24

Asset_Retirement_Obligations_S

Asset Retirement Obligations (Schedule Of Asset Retirement Obligation Transactions) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Asset Retirement Obligations Schedule Of Asset Retirement Obligation Transactions [Abstract]	'	'	'	'
Asset retirement obligations, beginning of period	$96,347	$68,089	$86,261	$59,685
Liabilities incurred from new wells	1,775	3,053	5,024	6,319
Liabilities assumed in acquisitions	0	26,986	282	29,113
Accretion expense for continuing operations	1,574	1,084	4,410	2,826
Accretion expense for discontinued operations	0	0	0	0
Disposition of wells	0	0	-303	-66
Liabilities settled upon plugging and abandoning wells	-897	-272	-2,542	-514
Revision of estimates	561	3,151	6,228	4,435
Asset retirement obligations, end of period	$99,360	$102,427	$99,360	$102,427

Incentive_Plans_Narrative_Deta

Incentive Plans (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]	'	'	'		'
Defined contribution and plans employers contribution	$1.30	$1.10	$3.70		$3
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	'	'	$1		'
Performance units granted	'	'	110,889	[1]	'
Minimum Payout Value on Performance Units	'	'	0.00%		'
Maximum Payout Value on Performance Units	'	'	300.00%		'
Performance Period	'	'	'36 years 0 months		'
Plan 401 k [Member]	'	'	'		'
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]	'	'	'		'
Defined contribution plan employer's contribution match percentage	100.00%	'	'		'
Defined contribution plan, employee contribution	10.00%	'	'		'
[1]	Reflects the amount of performance units granted. The actual payout of shares will be between zero and 300 percent of the performance units granted depending on the Company's performance at the end of the performance period.

Incentive_Plans_Summary_Of_Sto

Incentive Plans (Summary Of Stock Incentive Plan) (Detail)	Sep. 30, 2013		Dec. 31, 2012
Disclosure Incentive Plans Summary Of Stock Incentive Plan [Abstract]	'		'
Approved and authorized awards	7,500,000		'
Restricted stock grants, net of forfeitures	-2,368,907		'
Stock option grants, net of forfeitures	-3,463,720		'
Performance unit grants	-332,667	[1]	'
Treasury shares	125,580		86,861
Awards available for future grant	1,460,286		'
[1]	(a)This amount represents the 110,889 performance units granted multiplied by the maximum potential payout of 300 percent. The actual payout of shares may be between zero percent and 300 percent of the performance units granted depending on the Company's performance at the end of the performance period.

Incentive_Plans_Schedule_Of_Re

Incentive Plans (Schedule Of Restricted Stock Awards Activity) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
Disclosure Incentive Plans Schedule Of Restricted Stock Awards Activity [Abstract]	'
Outstanding at beginning of period	1,072,527
Shares granted	483,440
Shares cancelled / forfeited	-96,695
Lapse of restrictions	-220,710
Outstanding at end of period	1,238,562
Shares Granted - Grant Date Value Per Share	$87.69

Incentive_Plans_Summary_Inform

Incentive Plans (Summary Information For Stock-Based Compensation For Restricted Stock Awards) (Detail) (Restricted Stock [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'	'
Grant date fair value for awards during the period	$6,881	$1,470	$43,379	$45,827
Stock-based compensation expense from restricted stock	8,894	7,931	22,212	21,270
Income tax benefit related to restricted stock	3,399	3,032	8,491	8,131
Deductions in current taxable income related to restricted stock	2,302	1,043	15,847	22,581
Employee Grants [Member]	'	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'	'
Grant date fair value for awards during the period	6,881	1,180	30,934	27,306
Stock-based compensation expense from restricted stock	5,116	3,854	12,511	9,617
Officer And Director Grants [Member]	'	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'	'
Grant date fair value for awards during the period	0	290	12,445	18,521
Stock-based compensation expense from restricted stock	$3,778	$4,077	$9,701	$11,653

Incentive_Plans_Schedule_Of_St

Incentive Plans (Schedule Of Stock Option Awards Activity) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
Disclosure Incentive Plans Schedule Of Stock Option Awards Activity [Abstract]	'
Outstanding at beginning of period (Shares)	429,879
Options exercised (Shares)	-139,111
Outstanding at end of period (Shares)	290,768
Exercisable at end of period (Shares)	290,768
Outstanding at beginning of period	$20.28
Options exercised	$16.57
Outstanding at end of period	$22.05
Exercisable at end of Period - Weighted average exercise price	$22.05

Incentive_Plans_Summary_Inform1

Incentive Plans (Summary Information For Vested And Exercisable Stock Options Outstanding) (Detail) (USD $)	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]	'
Vested at end of period - Weighted average exercise price	$22.05
Exercisable at end of period (Shares)	290,768
Exercisable Weighted Average Remaining Contractual Life	'4 years 6 months
Exercisable at end of Period - Weighted average exercise price	$22.05
Exercisable Intrinsic Value	$25,228
Range One [Member]	'
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]	'
Exercise price, Lower range	$8
Exercisable at end of period (Shares)	2,005
Exercisable Weighted Average Remaining Contractual Life	'0 years 10 months
Exercisable at end of Period - Weighted average exercise price	$8
Exercisable Intrinsic Value	202
Range Two [Member]	'
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]	'
Exercise price, Lower range	$12
Exercisable at end of period (Shares)	23,788
Exercisable Weighted Average Remaining Contractual Life	'2 years 1 month
Exercisable at end of Period - Weighted average exercise price	$12
Exercisable Intrinsic Value	2,303
Range Three [Member]	'
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]	'
Exercise price, Lower range	$12.85
Exercise price, Upper range	'
Exercisable at end of period (Shares)	15,000
Exercisable Weighted Average Remaining Contractual Life	'3 years 11 months
Exercisable at end of Period - Weighted average exercise price	$12.85
Exercisable Intrinsic Value	1,439
Range Four [Member]	'
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]	'
Exercise price, Lower range	$20
Exercise price, Upper range	$23
Exercisable at end of period (Shares)	192,895
Exercisable Weighted Average Remaining Contractual Life	'4 years 9 months
Exercisable at end of Period - Weighted average exercise price	$21.40
Exercisable Intrinsic Value	16,862
Range Five [Member]	'
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]	'
Exercise price, Lower range	$28
Exercise price, Upper range	$37.27
Exercisable at end of period (Shares)	57,080
Exercisable Weighted Average Remaining Contractual Life	'4 years 8 months
Exercisable at end of Period - Weighted average exercise price	$31.34
Exercisable Intrinsic Value	$4,422

Incentive_Plans_Summary_Inform2

Incentive Plans (Summary Information For Stock-Based Compensation For Stock Options) (Detail) (Stock Options [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'	'
Stock-based compensation expense from stock options	$0	$28	$15	$164
Income tax benefit related to stock options	0	10	5	63
Deductions in current taxable income related to stock options exercised	1,797	23,332	10,317	39,420
Employee Grants [Member]	'	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'	'
Stock-based compensation expense from stock options	0	7	2	24
Officer And Director Grants [Member]	'	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'	'
Stock-based compensation expense from stock options	$0	$21	$13	$140

Incentive_Plans_Summary_Of_Ass

Incentive Plans (Summary Of Assumptions To Estimate Fair Value of Performance Unit Awards) (Detail)	9 Months Ended
	Sep. 30, 2013
Disclosure Incentive Plans Schedule Of Performance Unit Awards Fair Value Assumptions [Abstract]	'
Risk-free interest rate	0.37%
Volatility assumption - minimum	31.50%
Volatility assumption - maximum	45.10%

Incentive_Plans_Schedule_Of_Pe

Incentive Plans (Schedule Of Performance Unit Awards Activity) (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Disclosure Incentive Plans Schedule Of Performance Unit Awards Activity [Abstract]	'		'
Performance units outstanding at beginning of period (Shares)	110,889	[1]	0	[1]
Units granted	110,889	[1]	'
Performance units outstanding at end of period (Shares)	110,889	[1]	0	[1]
Shares Granted - Grant Date Fair Value - Performance Units	$111.40		'
[1]	Reflects the amount of performance units granted. The actual payout of shares will be between zero and 300 percent of the performance units granted depending on the Company's performance at the end of the performance period.

Incentive_Plans_Summary_Inform3

Incentive Plans (Summary Information For Stock-Based Compensation For Performance Units) (Detail) (Performance Shares [Member], Officer And Director Grants [Member], USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013
Performance Shares [Member] | Officer And Director Grants [Member]	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Grant date fair value for awards during the period	$0	$12,353
Allocated Share Based Compensation Expense	1,029	3,051
Employee Service Share Based Compensation Tax Benefit From Compensation Expense	$394	$1,167

Incentive_Plans_Summary_For_Fu

Incentive Plans (Summary For Future Stock-Based Compensation Expense) (Detail) (USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'
Remaining 2013	$10,388
2014	31,380
2015	18,742
2016	5,245
2017	548
Total	66,303
Restricted Stock [Member]	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'
Remaining 2013	9,359
2014	27,262
2015	14,588
2016	5,245
2017	548
Total	57,002
Performance Shares [Member]	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'
Remaining 2013	1,029
2014	4,118
2015	4,154
2016	0
2017	0
Total	$9,301

Recovered_Sheet6

Disclosures About Fair Value Of Financial Instruments (Carrying Amounts And Fair Values Of The Company's Financial Instruments) (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Credit facility	$207,600	$304,000
Eight Point Six Two Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	0	300,000
Seven Point Zero Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	600,000	600,000
Six Point Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	600,000	600,000
Five Point Five Percent Unsecured Senior Notes Due Twenty Twenty Three [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	1,550,000	700,000
Interest rate	5.50%	'
Debt Instrument Maturity Year	'2023	'
Carrying Reported Amount Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Derivative instruments, Assets	872	38,711
Derivative instruments, Liabilities	95,413	13,633
Credit facility	207,600	304,000
Carrying Reported Amount Fair Value Disclosure [Member] | Eight Point Six Two Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	0	297,103
Carrying Reported Amount Fair Value Disclosure [Member] | Seven Point Zero Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	600,000	600,000
Carrying Reported Amount Fair Value Disclosure [Member] | Six Point Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	600,000	600,000
Carrying Reported Amount Fair Value Disclosure [Member] | Five Piont Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	600,000	600,000
Carrying Reported Amount Fair Value Disclosure [Member] | Five Point Five Percent Unsecured Senior Notes Due Twenty Twenty Three [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	1,581,050	700,000
Portion At Fair Value Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Derivative instruments, Assets	872	38,711
Derivative instruments, Liabilities	95,413	13,633
Credit facility	210,666	299,679
Portion At Fair Value Fair Value Disclosure [Member] | Eight Point Six Two Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	0	323,471
Portion At Fair Value Fair Value Disclosure [Member] | Seven Point Zero Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	657,000	669,000
Portion At Fair Value Fair Value Disclosure [Member] | Six Point Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	643,500	660,000
Portion At Fair Value Fair Value Disclosure [Member] | Five Piont Five Percent Unsecured Senior Notes [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	598,500	633,000
Portion At Fair Value Fair Value Disclosure [Member] | Five Point Five Percent Unsecured Senior Notes Due Twenty Twenty Three [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Unsecured senior notes	$1,530,625	$733,250

Recovered_Sheet7

Disclosures About Fair Value Of Financial Instruments (Company's Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Net financial assets (liabilities)	($94,541)	$25,078
Derivative Assets Current	872	35,942
Derivative Assets Noncurrent	0	2,769
Current derivative contracts, liabilities	-71,364	-1,584
Noncurrent derivative contracts, liabilities	-24,049	-12,049
Net derivative instruments	-94,541	25,078
Current Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	12,880	56,471
Derivative instruments Fair Value, Liabilities	83,372	22,113
Noncurrent Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	4,600	12,108
Derivative instruments Fair Value, Liabilities	-28,649	-21,388
Fair Value Inputs Level 1 [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Net financial assets (liabilities)	0	0
Net derivative instruments	0	0
Fair Value Inputs Level 1 [Member] | Current Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	0	0
Derivative instruments Fair Value, Liabilities	0	0
Fair Value Inputs Level 1 [Member] | Noncurrent Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	0	0
Derivative instruments Fair Value, Liabilities	0	0
Fair Value Inputs Level 2 [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Net financial assets (liabilities)	-94,541	25,078
Net derivative instruments	-94,541	25,078
Fair Value Inputs Level 2 [Member] | Current Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	12,880	56,471
Derivative instruments Fair Value, Liabilities	83,372	22,113
Fair Value Inputs Level 2 [Member] | Noncurrent Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	4,600	12,108
Derivative instruments Fair Value, Liabilities	-28,649	-21,388
Fair Value Inputs Level 3 [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Net financial assets (liabilities)	0	0
Net derivative instruments	0	0
Fair Value Inputs Level 3 [Member] | Current Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	0	0
Derivative instruments Fair Value, Liabilities	0	0
Fair Value Inputs Level 3 [Member] | Noncurrent Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	0	0
Derivative instruments Fair Value, Liabilities	0	0
Gross Amounts Offset in the Consolidated Balance Sheet [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Net financial assets (liabilities)	0	0
Net derivative instruments	0	0
Gross Amounts Offset in the Consolidated Balance Sheet [Member] | Current Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	-12,008	-20,529
Derivative instruments Fair Value, Liabilities	-12,008	-20,529
Gross Amounts Offset in the Consolidated Balance Sheet [Member] | Noncurrent Commodity Derivative [Member]	'	'
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]	'	'
Derivative instruments, Assets	-4,600	-9,339
Derivative instruments Fair Value, Liabilities	$4,600	$9,339

Disclosures_About_Fair_Value_O2

Disclosures About Fair Value Of Financial Instruments (Carrying Amounts, Estimated Fair Values And Impairment Expense Of Long-Lived Assets For Continuing And Discontinued Operations) (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Disclosure Disclosures About Fair Value Of Financial Instruments Carrying Amounts Estimated Fair Values And Impairment Expense Of Long Lived Assets For Continuing And Discontinued Operations [Abstract]	'
Carrying Amount	$84,140
Estimated Fair Value	18,765
Impairment Expense	$65,375

Recovered_Sheet8

Derivative Financial Instruments (Gains And Losses Reported In Earnings Related To The Commodity And Interest Rate Derivative Instruments) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Financial Instruments Gains And Losses Reported In Earnings Related To Commodity And Interest Rate Derivative Instruments [Line Items]	'	'	'	'
Cash receipts from (payments on) derivatives not designated as hedges	$45,275	($16,139)	$37,684	$7,485
Gain (loss) on derivatives not designated as hedges	-168,610	-135,415	-157,303	109,542
Oil Commodity Derivative [Member]	'	'	'	'
Derivative Financial Instruments Gains And Losses Reported In Earnings Related To Commodity And Interest Rate Derivative Instruments [Line Items]	'	'	'	'
Cash receipts from (payments on) derivatives not designated as hedges	-49,864	15,859	-42,528	-8,374
Gain (loss) on derivatives not designated as hedges	-169,049	-135,401	-172,698	109,386
Natural Gas Commodity Derivative [Member]	'	'	'	'
Derivative Financial Instruments Gains And Losses Reported In Earnings Related To Commodity And Interest Rate Derivative Instruments [Line Items]	'	'	'	'
Cash receipts from (payments on) derivatives not designated as hedges	4,589	280	4,844	889
Gain (loss) on derivatives not designated as hedges	$439	($14)	$15,395	$156

Recovered_Sheet9

Derivative Financial Instruments (Outstanding Commodity Derivative Contracts) (Detail)

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Sep. 30, 2013

Mar. 31, 2013

Jun. 30, 2013

Dec. 31, 2013

Dec. 31, 2013

Sep. 30, 2013

Mar. 31, 2013

Jun. 30, 2013

Dec. 31, 2013

Oil Swaps [Member]

Oil Swaps [Member]

Oil Swaps [Member]

Oil Swaps [Member]

Oil Swaps [Member]

Oil Basis Swaps [Member]

Oil Basis Swaps [Member]

Oil Basis Swaps [Member]

Oil Basis Swaps [Member]

Oil Basis Swaps [Member]

Natural Gas Swap [Member]

Natural Gas Swap [Member]

Natural Gas Basis Swap [Member]

Natural Gas Basis Swap [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

Natural Gas Collars [Member]

bbl

bbl

bbl

bbl

bbl

bbl

bbl

bbl

bbl

bbl

MMBTU

MMBTU

MMBTU

MMBTU

MMBTU

MMBTU

MMBTU

MMBTU

MMBTU

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Derivative [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Volume (Bbl/MMBtu) - Current Year

'

'

'

'

'

3,404,000

[1]

'

'

'

3,404,000

[1]

6,992,000

[2]

6,992,000

[2]

6,440,000

[3]

6,440,000

[3]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Price per Bbl/MMBtu - Current Year

'

'

'

'

'

-1.12

[1]

'

'

'

-1.12

[1]

4.25

[2]

4.25

[2]

-0.15

[3]

-0.15

[3]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Volume (Bbl/MMBtu) - Year One

4,614,000

[4]

'

'

'

4,614,000

[4]

1,932,000

[1]

1,932,000

[1]

2,821,000

[1]

2,790,000

[1]

9,475,000

[1]

'

'

'

'

5,520,000

[5]

5,520,000

[5]

5,460,000

[5]

5,400,000

[5]

21,900,000

[5]

'

'

'

'

'

'

'

'

'

'

Price per Bbl/MMBtu - Year One

95.87

[4]

'

'

'

95.87

[4]

-0.45

[1]

-0.45

[1]

-0.46

[1]

-0.46

[1]

-0.46

[1]

'

'

'

'

'

'

'

'

'

3.85

[5]

3.85

[5]

3.85

[5]

3.85

[5]

3.85

[5]

4.4

[5]

4.4

[5]

4.4

[5]

4.4

[5]

4.4

[5]

Volume (Bbl/MMBtu) - Year Two

3,355,000

[4]

3,560,000

[4]

3,848,000

[4]

4,277,000

[4]

15,040,000

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Price per Bbl/MMBtu - Year Two

90.54

[4]

90.61

[4]

92.18

[4]

93.31

[4]

91.76

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Volume (Bbl/MMBtu) - Year Three

2,721,000

[4]

2,858,000

[4]

2,984,000

[4]

3,154,000

[4]

11,717,000

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Price per Bbl/MMBtu - Year Three

86.58

[4]

86.66

[4]

86.36

[4]

87.24

[4]

86.72

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Volume (Bbl/MMBtu) - Year Four

105,000

[4]

108,000

[4]

108,000

[4]

108,000

[4]

429,000

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Price per Bbl/MMBtu - Year Four

88.28

[4]

88.32

[4]

88.32

[4]

88.32

[4]

88.31

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Volume (Bbl/MMbtu) - Year Five

0

[4]

0

[4]

84,000

[4]

84,000

[4]

168,000

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Price per Bbl/MMBtu - Year Five

0

[4]

0

[4]

87

[4]

87

[4]

87

[4]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

(b) The basis differential price is between Midland b WTI and Cushing b WTI.

[2]

(c) The index prices for the natural gas price swaps are based on the NYMEX b Henry Hub last trading day futures price.

[3]

(e) The basis differential price is between the El Paso Permian delivery point and NYMEX b Henry Hub delivery point.

[4]

(a) The index prices for the oil price swaps are based on the NYMEX b West Texas Intermediate (bWTIb) monthly average futures price.

[5]

(d) The index prices for the natural gas collars are based on the El Paso Permian delivery point.

Debt_Summary_Of_LongTerm_Debt_

Debt (Summary Of Long-Term Debt) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Debt Instrument [Line Items]	'	'
Credit facility	$207,600	$304,000
Unamortized original issue premium (discount), net	31,050	-2,897
Less: current portion	0	0
Total long-term debt	3,588,650	3,101,103
8.625% senior notes due 2017	'	'
Debt Instrument [Line Items]	'	'
Unsecured senior notes	0	300,000
7.0% senior notes due 2021	'	'
Debt Instrument [Line Items]	'	'
Unsecured senior notes	600,000	600,000
6.5% senior notes due 2022	'	'
Debt Instrument [Line Items]	'	'
Unsecured senior notes	600,000	600,000
5.5% unsecured senior notes due 2022	'	'
Debt Instrument [Line Items]	'	'
Unsecured senior notes	600,000	600,000
5.5% unsecured senior notes due 2023	'	'
Debt Instrument [Line Items]	'	'
Unsecured senior notes	$1,550,000	$700,000

Debt_Narrative_Detail

Debt (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Debt Disclosure [Line Items]	'	'	'	'
Line of credit maturity date	'	'	25-Apr-16	'
Aggregate lender commitments	$2,500,000,000	'	$2,500,000,000	'
Aggregate maximum borrowing base	3,000,000,000	'	3,000,000,000	'
Percentage of lenders required for special redetermination	'	'	66.67%	'
Line of credit interest rate	'	'	3.25%	'
Loss on extinguishment of debt	0	0	-28,616,000	0
Minimum [Member]	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Commitment fees on unused portion of available commitment fee	'	'	37.50%	'
Debt to earnings ratio	'	'	'1.0	'
Current assets to current liabilities ratio	'	'	'1.0	'
Maximum [Member]	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Commitment fees on unused portion of available commitment fee	'	'	50.00%	'
Debt to earnings ratio	'	'	'4.0	'
Current assets to current liabilities ratio	'	'	'1.0	'
Prime Rate [Member] | Minimum [Member]	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Line Of Credit Facility Interest Rate At Period End	0.50%	'	0.50%	'
Prime Rate [Member] | Maximum [Member]	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Line Of Credit Facility Interest Rate At Period End	1.50%	'	1.50%	'
Eurodollar Future [Member] | Minimum [Member]	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Line Of Credit Facility Interest Rate At Period End	1.50%	'	1.50%	'
Eurodollar Future [Member] | Maximum [Member]	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Line Of Credit Facility Interest Rate At Period End	2.50%	'	2.50%	'
Same-Day Advance Facility	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Credit facility interest rate description	'	'	'The interest rate on this facility is the JPM Prime Rate plus the applicable interest margin.	'
Credit Facility borrowing capacity	25,000,000	'	25,000,000	'
8.625% senior notes due 2017	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Debt Instrument, Repurchased Face Amount	225,600,000	'	225,600,000	'
Percentage Of Notes Tendered	'	'	75.20%	'
Price Of Tender And Consent	'	'	106.92%	'
Price Of Remaining Notes Tendered	'	'	106.52%	'
Loss on extinguishment of debt	'	'	28,600,000	'
Premium Paid For Tender Offer	'	'	20,400,000	'
Unamortized Debt Issuance Expense	5,500,000	'	5,500,000	'
Debt Instrument, Unamortized Discount	2,700,000	'	2,700,000	'
5.5% unsecured senior notes due 2023	'	'	'	'
Debt Disclosure [Line Items]	'	'	'	'
Debt Instrument Issuance Month	'	'	'2013-06	'
Debt instrument amount issued	850,000,000	'	850,000,000	'
Interest rate	5.50%	'	5.50%	'
Debt instrument percent of par due	'	'	103.75%	'
Debt Instrument Maturity Year	'	'	'2023	'
Resulting Yield	'	'	4.88%	'
Net proceeds from issuance of debt	'	'	$867,800,000	'

Debt_Future_Interest_Expense_F

Debt (Future Interest Expense From Original Issue Discount On Senior Notes) (Detail) (USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Disclosure Debt Future Interest Expense From Original Issue Discount On Senior Notes [Abstract]	'
Remaining 2013	$629
2014	2,602
2015	2,747
2016	2,900
2017	3,062
2018	3,233
Thereafter	15,877
Total	$31,050

Debt_Principal_Maturities_Of_D

Debt (Principal Maturities Of Debt) (Detail) (USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Long-term Debt, Fiscal Year Maturity [Abstract]	'
Remaining 2013	$0
2014	0
2015	0
2016	207,600
2017	0
2018	0
Thereafter	3,350,000
Total	$3,557,600

Debt_Summary_Of_Interest_Expen

Debt (Summary Of Interest Expense) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Debt Summary Of Interest Expense [Abstract]	'	'	'	'
Cash payments for interest	$43,868	$48,203	$145,980	$115,731
Amortization of original issue discount (premium)	-620	117	-619	342
Amortization of deferred loan origination costs	3,311	3,114	9,844	8,724
Net changes in accruals	9,436	-97	6,975	4,276
Interest costs incurred	55,995	51,337	162,180	129,073
Total interest expense	$55,995	$51,337	$162,180	$129,073

Recovered_Sheet10

Commitments And Contingencies (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2013
Commitments [Line Items]	'	'	'	'	'
Annual officers' salaries	'	'	'	'	$5.60
Operating leases, lease payments	$1.50	$1.30	$4.20	$3.60	'

Commitments_And_Contingencies_1

Commitments And Contingencies (Future Drilling Commitments) (Detail) (USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Disclosure Commitments And Contingencies Future Drilling Commitments [Abstract]	'
Total	$8,084
Paymets Less than 1 year	8,084
Payments Due By Period 1 - 3 years	0
Payments Due By Period 3 - 5 years	0
More than 5 years	$0

Commitments_And_Contingencies_2

Commitments And Contingencies (Future Minimum Lease Commitments Under Non-Cancellable Operating Leases) (Detail) (USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Disclosure Commitments And Contingencies Future Minimum Lease Commitments Under Non Cancellable Operating Leases [Abstract]	'
Remaining 2013	$1,508
2014	5,372
2015	4,146
2016	2,778
2017	750
2018	441
Thereafter	1,247
Total	$16,242

Income_Taxes_Narrative_Detail

Income Taxes (Narrative) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Disclosure Income Taxes Narrative [Abstract]	'	'
Income taxes receivable, current	$3,800,000	'
Income taxes payable, current	$425,000	$2,141,000

Income_Taxes_Companys_Income_T

Income Taxes (Company's Income Tax Provision (Benefit)) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Income Taxes Companys Income Tax Provision Benefit [Abstract]	'	'	'	'
Income tax (expense ) benefit	$21,695	($995)	$86,023	$204,327
Income from discontinued operations	0	5,150	7,518	16,508
Excess tax benefits related to stock-based compensation	-5,081	-8,129	-9,244	-18,522
Income Tax Expense Benefit Net Of Excess Tax Benefits, Total	$16,614	($3,974)	$84,297	$202,313

Income_Taxes_Income_Tax_Provis

Income Taxes (Income Tax Provision (Benefit) Attributable To Income (Loss) From Continuing Operations) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Income Taxes Income Tax Provision Benefit Attributable To Income Loss From Continuing Operations [Abstract]	'	'	'	'
U.S. federal	($3,661)	($3,259)	$8,427	($1,155)
U.S. state and local	-106	555	1,788	2,375
Total current income tax provision	-3,767	-2,704	10,215	1,220
U.S. federal	23,652	2,240	67,529	178,766
U.S. state and local	1,810	-531	8,279	24,341
Total deferred income tax provision	25,462	1,709	75,808	203,107
Total income tax provision attributable to income from continuing operations	$21,695	($995)	$86,023	$204,327

Income_Taxes_Reconciliation_Be

Income Taxes (Reconciliation Between The Income Tax Expense (Benefit) And The Reported Amounts Of Income Tax Expense) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Income Taxes Reconciliation Between The Income Tax Expense Benefit And The Reported Amounts Of Income Tax Expense [Abstract]	'	'	'	'
Income at U.S. federal statutory rate	$18,241	($1,458)	$76,705	$185,979
State income taxes (net of federal tax effect)	1,726	-159	7,161	17,245
Revision of previous estimates	1,273	219	1,273	219
Statutory depletion	58	-91	-21	-207
Nondeductible expense & other	397	494	905	1,091
Income tax expense	$21,695	($995)	$86,023	$204,327
Effective tax rate	41.60%	23.90%	39.30%	38.50%

Income_Taxes_Companys_Income_T1

Income Taxes (Company's Income Tax Provision Attributable To Income From Discontinued Operations) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Income Taxes Companys Income Tax Provision Attributable To Income From Discontinued Operations [Abstract]	'	'	'	'
U.S. federal, current	$0	$4,589	$144	$14,729
U.S. state and local, current	0	25	25	82
Total current income tax benefit	0	4,614	169	14,811
U.S. federal, deferred	0	-107	6,397	-366
U.S. state and local, deferred	0	643	952	2,063
Total deferred income tax provision	0	536	7,349	1,697
Total income tax provision attributable to income from discontinued operations	$0	$5,150	$7,518	$16,508

Related_Party_Transactions_Sch

Related Party Transactions (Schedule Of Related Party Transactions) (Detail) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Related Party Transaction [Line Items]	'		'		'		'		'
Royalty interests of a director of the Company	$0		'		$0		'		$185,000
Payments for Notes to Directors and Officers	'		'		1,300,000		'		'
Director [Member]	'		'		'		'		'
Related Party Transaction [Line Items]	'		'		'		'		'
Royalty interest paid	2,010,000	[1]	525,000	[1]	4,694,000	[1]	1,820,000	[1]	'
Royalty interests of a director of the Company	0		'		0		'		185,000
Ownership interest in system	'		'		3.50%		'		'
Director and Certain Officers [Member]	'		'		'		'		'
Related Party Transaction [Line Items]	'		'		'		'		'
Royalty interest paid	12,000	[2]	0	[2]	33,000	[2]	0	[2]	'
Former President And Chief Operating Officer [Member]	'		'		'		'		'
Related Party Transaction [Line Items]	'		'		'		'		'
Amounts paid under consulting agreement with Steven L. Beal	745,000	[3]	60,000	[3]	865,000	[3]	180,000	[3]	'
Consulting fee per month	20,000		'		20,000		'		'
Payment To Mutually Terminate Consulting Agreement	$720,000		'		$720,000		'		'
[1]	Royalties paid on certain properties to a partnership of which a director is the general partner and owns a 3.5 percent partnership interest.
[2]	Payments made to a director and certain officers who directly own overriding royalty interests in properties owned by the Company.
[3]	On JuneB 30, 2009, Steven L. Beal, the Companybs then-president and chief operating officer, retired from such positions. On JuneB 9, 2009, the Company entered into a consulting agreement (the bConsulting Agreementb) with Mr.B Beal, under which Mr.B Beal began serving as a consultant to the Company on JulyB 1, 2009. During the term of the consulting relationship, Mr. Beal received a consulting fee of $20,000 per month and a monthly reimbursement for his medical and dental coverage costs. In August 2013, the Company and Mr. Beal mutually terminated the Consulting Agreement in exchange for the payment to Mr. Beal of $720,000, which termination and payment were approved by the disinterested members of the Companybs Board of Directors.

Discontinued_Operations_Schedu

Discontinued Operations (Schedule Of Discontinued Operations) (Detail) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Disclosure Discontinued Operations Schedule Of Discontinued Operations [Abstract]	'		'		'		'
Oil sales	$0		$26,616		$0		$82,518
Natural gas sales	0		5,588		0		13,342
Total operating revenues	0		32,204		0		95,860
Oil and natural gas production	0		8,702		0		24,864
Depreciation, depletion and amortization	0	[1]	9,476	[1]	0	[1]	26,265	[1]
Accretion of discount on asset retirement obligations	0	[1]	336	[1]	0	[1]	629	[1]
General and administrative	0	[2]	-619	[2]	0	[2]	-1,766	[2]
Total operating costs and expenses	0		17,895		0		49,992
Income from operations	0		14,309		0		45,868
Gain on disposition of assets, net	0	[1]	0	[1]	19,599	[1]	0	[1]
Income from discontinued operations before income taxes	0		14,309		19,599		45,868
Current	0		-4,614		-169		-14,811
Deferred	0	[1]	-536	[1]	-7,349	[1]	-1,697	[1]
Income from discontinued operations, net of tax	$0		$9,159		$12,081		$29,360
[1]	(a) Represents the significant non-cash components of discontinued operations.
[2]	(b) Represents the fees received from third-parties for operating oil and natural gas properties that were sold. The Company reflects these fees as a reduction of general and administrative expenses.

Net_Income_Per_Share_Reconcili

Net Income Per Share (Reconciliation Of Earnings Attributable To Common Shares Basic And Diluted) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Income (loss) as reported	$30,421	$5,988	$145,214	$356,402
Participating basic earnings	-357	0	-1,550	0
Basic net income (loss) attributable to common stockholders	30,064	5,988	143,664	356,402
Dilutive Securities	0	0	2	0
Net Income (Loss) Available to Common Stockholders, Diluted	30,064	5,988	143,666	356,402
Basic	$0.29	$0.06	$1.39	$3.46
Diluted	$0.29	$0.06	$1.38	$3.43
Segment, Continuing Operations [Member]	'	'	'	'
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Income (loss) as reported	30,421	-3,171	133,133	327,042
Participating basic earnings	-357	0	-1,421	0
Basic net income (loss) attributable to common stockholders	30,064	-3,171	131,712	327,042
Dilutive Securities	0	0	2	0
Net Income (Loss) Available to Common Stockholders, Diluted	30,064	-3,171	131,714	327,042
Basic	$0.29	($0.03)	$1.27	$3.17
Diluted	$0.29	($0.03)	$1.27	$3.15
Segment, Discontinued Operations [Member]	'	'	'	'
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Income (loss) as reported	0	9,159	12,081	29,360
Participating basic earnings	0	0	-129	0
Basic net income (loss) attributable to common stockholders	0	9,159	11,952	29,360
Dilutive Securities	0	0	0	0
Net Income (Loss) Available to Common Stockholders, Diluted	$0	$9,159	$11,952	$29,360
Basic	$0	$0.09	$0.12	$0.29
Diluted	$0	$0.09	$0.11	$0.28

Net_Income_Per_Share_Reconcili1

Net Income Per Share (Reconciliation Of The Weighted Average Common Shares Outstanding) (Detail)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reconciliation Of Basic Weighted Average Common Shares Outstanding To Diluted Weighted Average Common Shares Outstanding [Line Items]	'	'	'	'
Basic	103,801	103,292	103,709	103,088
Diluted	103,958	104,040	103,882	103,898
Stock Options [Member]	'	'	'	'
Reconciliation Of Basic Weighted Average Common Shares Outstanding To Diluted Weighted Average Common Shares Outstanding [Line Items]	'	'	'	'
Dilutive shares	157	323	173	399
Restricted Stock [Member]	'	'	'	'
Reconciliation Of Basic Weighted Average Common Shares Outstanding To Diluted Weighted Average Common Shares Outstanding [Line Items]	'	'	'	'
Dilutive shares	0	425	0	411
Performance Shares [Member]	'	'	'	'
Reconciliation Of Basic Weighted Average Common Shares Outstanding To Diluted Weighted Average Common Shares Outstanding [Line Items]	'	'	'	'
Dilutive shares	0	0	0	0

Net_Income_Per_Share_Summary_O

Net Income Per Share (Summary Of The Common Stock Options And Restricted Stock) (Detail)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Stock Options [Member]	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive common shares	0	0	0	0
Restricted Stock [Member]	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive common shares	2	31	7	126
Performance Shares [Member]	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive common shares	111	0	111	0

Other_Current_Liabilities_Sche

Other Current Liabilities (Schedule Of Other Current Liabilities) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Other Liabilities Disclosure [Abstract]	'	'
Accrued production costs	$53,642	$52,825
Payroll related matters	21,360	16,365
Accrued interest	79,460	64,304
Settlements due on derivatives not designated as hedges	17,304	0
Acquisition and divestiture settlements	0	18,100
Income taxes payable	425	2,141
Asset retirement obligations	2,674	3,308
Other	3,862	3,297
Other current liabilities	$178,727	$160,340

Subsidiary_Guarantors_Condense

Subsidiary Guarantors (Condensed Consolidating Balance Sheet) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
ASSETS	'	'
Accounts receivable - related parties	$0	$0
Other current assets	607,712	458,882
Oil and natural gas properties, net	8,676,205	7,890,283
Property and equipment, net	111,705	103,141
Investment in subsidiaries	0	0
Other long-term assets	135,079	137,131
Total assets	9,530,701	8,589,437
LIABILITIES AND EQUITY	'	'
Accounts payable - related parties	0	185
Other current liabilities	874,284	739,901
Other long-term liabilities	1,423,054	1,282,052
Long-term debt	3,588,650	3,101,103
Equity	3,644,713	3,466,196
Total liabilities and stockholders' equity	9,530,701	8,589,437
Parent Company [Member]	'	'
ASSETS	'	'
Accounts receivable - related parties	6,158,999	5,839,995
Other current assets	36,298	46,737
Oil and natural gas properties, net	0	0
Property and equipment, net	0	0
Investment in subsidiaries	3,735,429	3,146,918
Other long-term assets	76,376	80,378
Total assets	10,007,102	9,114,028
LIABILITIES AND EQUITY	'	'
Accounts payable - related parties	1,279,039	1,271,563
Other current liabilities	168,402	76,496
Other long-term liabilities	1,326,298	1,198,670
Long-term debt	3,588,650	3,101,103
Equity	3,644,713	3,466,196
Total liabilities and stockholders' equity	10,007,102	9,114,028
Guarantor Subsidiaries [Member]	'	'
ASSETS	'	'
Accounts receivable - related parties	1,279,039	2,416,697
Other current assets	571,414	412,145
Oil and natural gas properties, net	8,676,205	7,890,283
Property and equipment, net	111,705	103,141
Investment in subsidiaries	0	0
Other long-term assets	58,703	56,753
Total assets	10,697,066	10,879,019
LIABILITIES AND EQUITY	'	'
Accounts payable - related parties	6,158,999	6,985,314
Other current liabilities	705,882	663,405
Other long-term liabilities	96,756	83,382
Long-term debt	0	0
Equity	3,735,429	3,146,918
Total liabilities and stockholders' equity	10,697,066	10,879,019
Consolidation Eliminations [Member]	'	'
ASSETS	'	'
Accounts receivable - related parties	-7,438,038	-8,256,692
Other current assets	0	0
Oil and natural gas properties, net	0	0
Property and equipment, net	0	0
Investment in subsidiaries	-3,735,429	-3,146,918
Other long-term assets	0	0
Total assets	-11,173,467	-11,403,610
LIABILITIES AND EQUITY	'	'
Accounts payable - related parties	-7,438,038	-8,256,692
Other current liabilities	0	0
Other long-term liabilities	0	0
Long-term debt	0	0
Equity	-3,735,429	-3,146,918
Total liabilities and stockholders' equity	($11,173,467)	($11,403,610)

Subsidiary_Guarantors_Condense1

Subsidiary Guarantors (Condensed Consolidating Statement Of Operations) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Condensed Financial Statements Captions [Line Items]	'	'	'	'
Total operating revenues	$652,920	$465,343	$1,687,833	$1,342,288
Total operating costs and expenses	-542,868	-415,058	-1,276,075	-676,929
Income (loss) from continuing operations	110,052	50,285	411,758	665,359
Interest expense	-55,995	-51,337	-162,180	-129,073
Loss on extinguishment of debt	0	0	28,616	0
Other, net	-1,941	-3,114	-1,806	-4,917
Income (loss) from continuing operations before income taxes	52,116	-4,166	219,156	531,369
Income tax (expense ) benefit	-21,695	995	-86,023	-204,327
Income (loss) from continuing operations	30,421	-3,171	133,133	327,042
Net income	30,421	5,988	145,214	356,402
Parent Company [Member]	'	'	'	'
Condensed Financial Statements Captions [Line Items]	'	'	'	'
Total operating revenues	0	0	0	0
Total operating costs and expenses	169,935	135,637	159,017	-108,776
Income (loss) from continuing operations	-169,935	-135,637	-159,017	108,776
Interest expense	-55,995	-51,337	-162,180	-129,073
Loss on extinguishment of debt	'	'	-28,616	'
Other, net	278,046	197,117	588,568	597,534
Income (loss) from continuing operations before income taxes	52,116	10,143	238,755	577,237
Income tax (expense ) benefit	-21,695	995	-86,023	-204,327
Income (loss) from continuing operations	'	11,138	152,732	372,910
Income from discontinued operations, net of tax	'	-5,150	-7,518	-16,508
Net income	30,421	5,988	145,214	356,402
Guarantor Subsidiaries [Member]	'	'	'	'
Condensed Financial Statements Captions [Line Items]	'	'	'	'
Total operating revenues	652,920	458,001	1,687,833	1,334,946
Total operating costs and expenses	372,933	273,701	1,117,058	779,985
Income (loss) from continuing operations	279,987	184,300	570,775	'
Interest expense	0	0	0	0
Loss on extinguishment of debt	'	'	0	'
Other, net	-1,996	2,309	-1,863	522
Income (loss) from continuing operations before income taxes	277,991	186,609	568,912	555,483
Income tax (expense ) benefit	0	0	0	0
Income (loss) from continuing operations	'	186,609	568,912	555,483
Income from discontinued operations, net of tax	'	14,309	19,599	45,868
Net income	277,991	200,918	588,511	601,351
Non-Guarantor Subsidiaries [Member]	'	'	'	'
Condensed Financial Statements Captions [Line Items]	'	'	'	'
Total operating revenues	'	7,342	'	7,342
Total operating costs and expenses	'	5,720	'	5,720
Income (loss) from continuing operations	'	1,622	'	'
Interest expense	'	0	'	0
Other, net	'	-6,043	'	-6,043
Income (loss) from continuing operations before income taxes	'	-4,421	'	-4,421
Income tax (expense ) benefit	'	0	'	0
Income (loss) from continuing operations	'	-4,421	'	-4,421
Income from discontinued operations, net of tax	'	0	'	0
Net income	'	-4,421	'	-4,421
Consolidation Eliminations [Member]	'	'	'	'
Condensed Financial Statements Captions [Line Items]	'	'	'	'
Total operating revenues	0	0	0	0
Total operating costs and expenses	0	0	0	0
Income (loss) from continuing operations	0	0	0	'
Interest expense	0	0	0	0
Loss on extinguishment of debt	'	'	0	'
Other, net	-277,991	-196,497	-588,511	-596,930
Income (loss) from continuing operations before income taxes	-277,991	-196,497	-588,511	-596,930
Income tax (expense ) benefit	0	0	0	0
Income (loss) from continuing operations	'	-196,497	-588,511	-596,930
Income from discontinued operations, net of tax	'	0	0	0
Net income	($277,991)	($196,497)	($588,511)	($596,930)

Subsidiary_Guarantors_Condense2

Subsidiary Guarantors (Condensed Consolidating Statement Of Cash Flows) (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Condensed Financial Statements Captions [Line Items]	'	'
Net cash flows provided by (used in) operating activities	$944,644	$845,636
Net cash flows used in investing activities	-1,472,096	-2,367,407
Net cash flows provided by (used in) financing activities	524,594	1,521,720
Net increase (decrease) in cash and cash equivalents	-2,858	-51
Cash and cash equivalents at beginning of period	2,880	342
Cash and cash equivalents at end of period	22	291
Parent Company [Member]	'	'
Condensed Financial Statements Captions [Line Items]	'	'
Net cash flows provided by (used in) operating activities	-441,741	-1,512,952
Net cash flows used in investing activities	-37,684	-7,485
Net cash flows provided by (used in) financing activities	479,425	1,520,437
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Guarantor Subsidiaries [Member]	'	'
Condensed Financial Statements Captions [Line Items]	'	'
Net cash flows provided by (used in) operating activities	1,386,385	2,355,751
Net cash flows used in investing activities	-1,434,412	-1,816,184
Net cash flows provided by (used in) financing activities	45,169	-539,618
Net increase (decrease) in cash and cash equivalents	-2,858	-51
Cash and cash equivalents at beginning of period	2,880	342
Cash and cash equivalents at end of period	22	291
Non-Guarantor Subsidiaries [Member]	'	'
Condensed Financial Statements Captions [Line Items]	'	'
Net cash flows provided by (used in) operating activities	'	2,837
Net cash flows used in investing activities	'	-543,738
Net cash flows provided by (used in) financing activities	'	540,901
Net increase (decrease) in cash and cash equivalents	'	0
Cash and cash equivalents at beginning of period	'	0
Cash and cash equivalents at end of period	'	0
Consolidation Eliminations [Member]	'	'
Condensed Financial Statements Captions [Line Items]	'	'
Net cash flows provided by (used in) operating activities	0	0
Net cash flows used in investing activities	0	0
Net cash flows provided by (used in) financing activities	0	0
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$0	$0

Subsequent_Events_New_Commodit

Subsequent Events (New Commodity Derivative Contracts) (Detail) (Oil Swaps [Member], Subsequent Event [Member])	3 Months Ended								12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2013
	bbl		bbl		bbl		bbl		bbl
Oil Swaps [Member] | Subsequent Event [Member]	'		'		'		'		'
Subsequent Event [Line Items]	'		'		'		'		'
Volume (Bbl/MMBtu) - Current Year	150,000	[1]	'		'		'		150,000	[1]
Price per Bbl/MMBtu - Current Year	102.55	[1]	'		'		'		102.55	[1]
Volume (Bbl/MMBtu) - Year One	91,000	[1]	129,000	[1]	152,000	[1]	153,000	[1]	525,000	[1]
Price per Bbl/MMBtu - Year One	97.53	[1]	97.71	[1]	97.78	[1]	97.78	[1]	97.72	[1]
Volume (Bbl/MMBtu) - Year Two	96,000	[1]	85,000	[1]	100,000	[1]	94,000	[1]	375,000	[1]
Price per Bbl/MMBtu - Year Two	89.84	[1]	89.83	[1]	89.84	[1]	89.84	[1]	89.84	[1]
[1]	(a) The index prices for the oil price swaps are based on the NYMEX b West Texas Intermediate (bWTIb) monthly average futures price.

Supplementary_Information_Capi

Supplementary Information (Capitalized Costs) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Disclosure Supplementary Information Capitalized Costs [Abstract]	'	'
Proved	$9,732,454	$8,402,154
Unproved	1,119,792	1,053,445
Accumulated depletion and depreciation	-2,176,041	-1,565,316
Net capitalized costs for oil and natural gas properties	$8,676,205	$7,890,283

Supplementary_Information_Cost

Supplementary Information (Costs Incurred For Oil And Natural Gas Producing Activities) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Supplementary Information Costs Incurred For Oil And Natural Gas Producing Activities [Abstract]	'	'	'	'
Proved	$0	$690,158	$2,376	$855,773
Unproved	13,991	349,903	58,832	411,110
Exploration	229,082	223,569	779,026	567,065
Development	197,696	187,759	593,006	574,541
Total costs incurred for oil and natural gas properties	$440,769	$1,451,389	$1,433,240	$2,408,489

Supplementary_Information_Asse

Supplementary Information (Asset Retirement Obligations For Oil and Natural Gas Producing Activities) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Supplementary Information Asset Retirement Obligations For Oil And Natural Gas Producing Activities [Abstract]	'	'	'	'
Exploration costs	$535	$1,185	$2,089	$2,452
Development costs	1,801	5,019	9,163	8,302
Total	$2,336	$6,204	$11,252	$10,754