Bill Barrett (BBG) 10-K 21 Feb 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Jan. 24, 2014	Jun. 28, 2013
Document Document And Entity Information [Abstract]	'	'	'
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Trading Symbol	'BBG	'	'
Entity Registrant Name	'BILL BARRETT CORPORATION	'	'
Entity Central Index Key	'0001172139	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	49,154,348	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Public Float	'	'	$978,357,338

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$54,595	$79,445
Accounts receivable, net of allowance for doubtful accounts	97,586	112,011
Derivative assets	173	29,980
Prepayments and other current assets	4,893	6,903
Total current assets	157,247	228,339
Property and equipment - at cost, successful efforts method for oil and gas properties:	'	'
Proved oil and gas properties	2,863,923	3,331,267
Unproved oil and gas properties, excluded from amortization	296,599	457,207
Furniture, equipment and other	41,726	45,636
Property, plant and equipment, gross	3,202,248	3,834,110
Accumulated depreciation, depletion, amortization and impairment	-999,752	-1,222,773
Total property and equipment, net	2,202,496	2,611,337
Deferred financing costs and other noncurrent assets	21,770	29,773
Total	2,381,513	2,869,449
Current liabilities:	'	'
Accounts payable and accrued liabilities	115,928	125,017
Amounts payable to oil and gas property owners	26,778	19,663
Production taxes payable	39,235	45,624
Derivative liabilities	5,988	0
Deferred income taxes	199	13,752
Current portion of long-term debt	4,591	9,077
Total current liabilities	192,719	213,133
Long-term debt	979,082	1,156,654
Asset retirement obligations	39,200	46,050
Deferred income taxes	161,326	266,364
Derivatives and other noncurrent liabilities	3,468	4,473
Stockholders’ equity:	'	'
Common stock, $0.001 par value; authorized 150,000,000 shares; 49,152,448 and 48,150,475 shares issued and outstanding at December 31, 2013 and 2012, respectively, with 1,340,060 and 870,794 shares subject to restrictions, respectively	48	47
Additional paid-in capital	904,261	883,923
Retained earnings	100,740	293,473
Treasury stock, at cost: zero shares at December 31, 2013 and 2012, respectively	0	0
Accumulated other comprehensive income	669	5,332
Total stockholders’ equity	1,005,718	1,182,775
Total	$2,381,513	$2,869,449

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	49,152,448	48,150,475
Common stock, shares outstanding	49,152,448	48,150,475
Common stock, shares subject to restrictions	1,340,060	870,794
Treasury stock, shares	0	0

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating and Other Revenues:	'	'	'
Oil, gas and NGL production	$565,555	$700,639	$780,751
Other	2,538	-444	4,873
Total operating and other revenues	568,093	700,195	785,624
Operating Expenses:	'	'	'
Lease operating expense	70,217	72,734	56,603
Gathering, transportation and processing expense	67,269	106,548	93,423
Production tax expense	27,172	25,513	37,498
Exploration expense	337	8,814	3,645
Impairment, dry hole costs and abandonment expense	238,398	67,869	117,599
Depreciation, depletion and amortization	279,775	326,842	288,421
General and administrative expense	64,902	68,666	66,780
Total operating expenses	748,070	676,986	663,969
Operating Income (Loss)	-179,977	23,209	121,655
Other Income and Expense:	'	'	'
Interest and other income	1,646	155	-397
Interest expense	-88,507	-95,506	-58,616
Commodity derivative gain (loss)	-23,068	72,759	-14,263
Gain (loss) on extinguishment of debt	-21,460	1,601	0
Total other income and expense	-131,389	-20,991	-73,276
Income (Loss) before Income Taxes	-311,366	2,218	48,379
Provision for (Benefit from) Income Taxes	-118,633	1,636	17,672
Net income (loss)	($192,733)	$582	$30,707
Net Income (Loss) Per Common Share, Basic (in dollars per share)	($4.06)	$0.01	$0.66
Net Income (Loss) Per Common Share, Diluted (in dollars per share)	($4.06)	$0.01	$0.65
Weighted Average Common Shares Outstanding, Basic (in shares)	47,496,857	47,194,668	46,535,632
Weighted Average Common Shares Outstanding, Diluted (in shares)	47,496,857	47,353,951	47,236,663

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Other Comprehensive Income [Abstract]	'	'	'
Net Income (Loss)	($192,733)	$582	$30,707
Other Comprehensive Income (Loss), net of tax:	'	'	'
Effect of derivative financial instruments	-4,663	-50,712	8,215
Other comprehensive income (loss)	-4,663	-50,712	8,215
Comprehensive Income (Loss)	($197,396)	($50,130)	$38,922

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Activities:	'	'	'
Net Income (Loss)	($192,733)	$582	$30,707
Adjustments to reconcile to net cash provided by operations:	'	'	'
Depreciation, depletion and amortization	279,775	326,842	288,421
Deferred income taxes	-117,050	-185	17,688
Impairment, dry hole costs and abandonment expense	238,398	67,869	117,599
Commodity derivative (gain) loss	23,068	-72,759	14,263
Settlements of commodity derivatives	5,315	42,305	-28,054
Stock compensation and other non-cash charges	16,027	18,328	21,953
Amortization of debt discounts and deferred financing costs	5,604	8,425	13,886
(Gain) loss on extinguishment of debt	21,460	-1,601	0
(Gain) loss on sale of properties	-130	4,279	-1,955
APIC pool for excess tax benefits related to share-based compensation	1,259	-32	0
Change in operating assets and liabilities:	'	'	'
Accounts receivable	14,294	-10,511	-27,680
Prepayments and other assets	1,394	1,293	1,809
Accounts payable, accrued and other liabilities	-35,600	2,589	24,531
Amounts payable to oil and gas property owners	9,997	3,988	-4,010
Production taxes payable	-5,813	-2,976	10,190
Net cash provided by operating activities	265,265	388,436	479,348
Investing Activities:	'	'	'
Additions to oil and gas properties, including acquisitions	-445,479	-958,654	-947,206
Additions of furniture, equipment and other	-2,254	-7,231	-11,142
Proceeds from sale of properties and other investing activities	310,704	328,888	1,702
Net cash used in investing activities	-137,029	-636,997	-956,646
Financing Activities:	'	'	'
Proceeds from debt	420,000	875,826	800,000
Principal and redemption premium payments on debt	-576,422	-595,386	-330,000
Proceeds from stock option exercises	6,385	673	22,247
APIC pool for excess tax benefits related to share-based compensation	-1,259	0	0
Deferred financing costs and other	-1,790	-10,438	-16,308
Net cash provided by (used in) financing activities	-153,086	270,675	475,939
Increase (Decrease) in Cash and Cash Equivalents	-24,850	22,114	-1,359
Beginning Cash and Cash Equivalents	79,445	57,331	58,690
Ending Cash and Cash Equivalents	$54,595	$79,445	$57,331

CONSOLIDATED_STATEMENTS_OF_STO

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (USD $)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]
In Thousands, unless otherwise specified
Balance at Dec. 31, 2010	$1,140,962	$46	$830,903	$262,184	'	$47,829
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'
Exercise of options, restricted stock activity and shares exchanged for exercise and tax withholding	18,403	1	22,838	'	-4,436	'
Stock-based compensation	20,551	'	20,551	'	'	'
Retirement of treasury stock	0	'	-4,436	'	4,436	'
Net Income (Loss)	30,707	'	'	30,707	'	'
Effect of derivative financial instruments, net of taxes	8,215	'	'	'	'	8,215
Balance at Dec. 31, 2011	1,218,838	47	869,856	292,891	0	56,044
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'
Exercise of options, restricted stock activity and shares exchanged for exercise and tax withholding	-1,840	'	673	'	-2,513	'
APIC pool for excess tax benefits related to share-based compensation	32	'	32	'	'	'
Stock-based compensation	16,874	'	16,874	'	'	'
Retirement of treasury stock	0	'	-2,513	'	2,513	'
Settlement of convertible notes	-999	'	-999	'	'	'
Net Income (Loss)	582	'	'	582	'	'
Effect of derivative financial instruments, net of taxes	-50,712	'	'	'	'	-50,712
Balance at Dec. 31, 2012	1,182,775	47	883,923	293,473	0	5,332
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'
Exercise of options, restricted stock activity and shares exchanged for exercise and tax withholding	4,607	1	6,384	'	-1,778	'
APIC pool for excess tax benefits related to share-based compensation	-1,259	'	-1,259	'	'	'
Stock-based compensation	16,991	'	16,991	'	'	'
Retirement of treasury stock	0	'	-1,778	'	1,778	'
Net Income (Loss)	-192,733	'	'	-192,733	'	'
Effect of derivative financial instruments, net of taxes	-4,663	'	'	'	'	-4,663
Balance at Dec. 31, 2013	$1,005,718	$48	$904,261	$100,740	$0	$669

CONSOLIDATED_STATEMENTS_OF_STO1

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Stockholders' Equity [Abstract]	'	'	'
Effect of derivative financial instruments, taxes	($2,802)	($30,458)	$4,886

Organization

Organization	12 Months Ended
	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization	'
	Organization
	Bill Barrett Corporation, a Delaware corporation, together with its wholly-owned subsidiaries (collectively, the “Company”) is an independent oil and gas company engaged in the exploration, development and production of oil, natural gas and NGLs. Since its inception in January 2002, the Company has conducted its activities principally in the Rocky Mountain region of the United States.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	Summary of Significant Accounting Policies
	Basis of Presentation. The accompanying consolidated financial statements include the accounts of the Company. These statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). All intercompany accounts and transactions have been eliminated in consolidation.
	Use of Estimates. In the course of preparing the Company’s financial statements in accordance with GAAP, management makes various assumptions, judgments and estimates to determine the reported amount of assets, liabilities, revenues and expenses and in the disclosure of commitments and contingencies. Changes in these assumptions, judgments and estimates will occur as a result of the passage of time and the occurrence of future events and, accordingly, actual results could differ from amounts initially established.
	Areas requiring the use of assumptions, judgments and estimates relate to the expected cash settlement of the Company’s 5% Convertible Senior Notes due 2028 (“Convertible Notes”) in computing diluted earnings per share, volumes of oil, natural gas and NGL reserves used in calculating depreciation, depletion and amortization (“DD&A”), the amount of expected future cash flows used in determining possible impairments of oil and gas properties and the amount of future capital costs used in these calculations. Assumptions, judgments and estimates also are required in determining asset retirement obligations, the timing of dry hole costs, impairments of proved and unproved properties, valuing deferred tax assets and estimating fair values of derivative instruments and stock-based payment awards.
	Accounts Receivable. Accounts receivable is comprised of the following:
		As of December 31,
		2013				2012
		(in thousands)
	Accrued oil, gas and NGL sales	$	67,583			$	69,482
	Due from joint interest owners	23,507				36,300
	Other	6,517				6,554
	Allowance for doubtful accounts	(21		)		(325		)
	Total accounts receivable	$	97,586			$	112,011
	Oil and Gas Properties. The Company’s oil, gas and NGL exploration and production activities are accounted for using the successful efforts method. Under this method, all property acquisition costs and costs of exploratory and development wells are capitalized when incurred, pending determination of whether the well has found proved reserves. If an exploratory well does not find proved reserves, the costs of drilling the well are charged to expense and included within cash flows from investing activities in the Consolidated Statements of Cash Flows. If an exploratory well does find proved reserves, the costs remain capitalized and are included within additions to oil and gas properties within cash flows from investing activities in the Consolidated Statements of Cash Flows when incurred. The costs of development wells are capitalized whether proved reserves are added or not. Oil and gas lease acquisition costs are also capitalized.
	Other exploration costs, including certain geological and geophysical expenses and delay rentals for oil and gas leases, are charged to expense as incurred. The sale of a partial interest in a proved property is accounted for as a cost recovery and no gain or loss is recognized as long as this treatment does not significantly affect the unit-of-production amortization rate. A gain or loss is recognized for all other sales of proved properties and is classified in other operating revenues. Maintenance and repairs are charged to expense, and renewals and betterments are capitalized to the appropriate property and equipment accounts.
	Unproved oil and gas property costs are transferred to proved oil and gas properties if the properties are subsequently determined to be productive or are assigned proved reserves. Proceeds from sales of partial interests in unproved leases are accounted for as a recovery of cost without recognizing any gain until all costs are recovered. Unproved oil and gas properties are assessed periodically for impairment based on remaining lease terms, drilling results, reservoir performance, commodity price outlooks, future plans to develop acreage and other relevant matters.
	Materials and supplies consist primarily of tubular goods and well equipment to be used in future drilling operations or repair operations and are carried at the lower of cost or market value, on a first-in, first-out basis.
	The following table sets forth the net capitalized costs and associated accumulated DD&A and non-cash impairments relating to the Company’s oil, natural gas and NGL producing activities:
		As of December 31,
		2013				2012
		(in thousands)
	Proved properties	$	485,427			$	387,242
	Wells and related equipment and facilities	2,192,754				2,625,891
	Support equipment and facilities	177,224				304,914
	Materials and supplies	8,518				13,220
	Total proved oil and gas properties	$	2,863,923			$	3,331,267
	Unproved properties	239,925				384,486
	Wells and facilities in progress	56,674				72,721
	Total unproved oil and gas properties, excluded from amortization	$	296,599			$	457,207
	Accumulated depreciation, depletion, amortization and impairment	(976,339		)		(1,203,495		)
	Total oil and gas properties, net	$	2,184,183			$	2,584,979
	Net changes in capitalized exploratory well costs for the years ended December 31, 2013, 2012 and 2011, respectively, are reflected in the following table:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Beginning of period	$	—			$	—			$	9,041
	Additions to capitalized exploratory well costs pending the determination of proved reserves	—				—				110
	Reclassifications to wells, facilities and equipment based on the determination of proved reserves	—				—				(6,179		)
	Exploratory well costs charged to dry hole costs and abandonment expense	—				—				(2,972		)
	End of period	$	—			$	—			$	—
	All exploratory wells are evaluated for economic viability within one year of well completion. Exploratory wells that discover potentially economic reserves in areas where a major capital expenditure would be required before production could begin, and where the economic viability of that major capital expenditure depends upon the successful completion of further exploratory work in the area, remain capitalized if the well finds a sufficient quantity of reserves to justify its completion as a producing well and the Company is making sufficient progress assessing the reserves and the economic and operating viability of the project.
	The Company reviews proved oil and gas properties on a field-by-field basis for impairment on an annual basis or whenever events and circumstances indicate that a decline in the recoverability of their carrying value may have occurred. The Company estimates the expected undiscounted future cash flows of its oil and gas properties and compares such undiscounted future cash flows to the carrying amount of the oil and gas properties to determine if the carrying amount is recoverable. If the carrying value of a property exceeds the undiscounted future cash flows, the Company will impair the carrying value to fair value based on an analysis of quantitative and qualitative factors. The factors used to determine fair value include, but are not limited to, recent sales prices of comparable properties, the present value of future cash flows, net of estimated operating and development costs using estimates of reserves, future commodity pricing, future production estimates, anticipated capital expenditures and various discount rates commensurate with the risk and current market conditions associated with realizing the expected cash flows projected.
	The Company recognized non-cash impairment charges, which were included within impairment, dry hole costs and abandonment expense in the Consolidated Statements of Operations, as follows:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Non-cash impairment of proved oil and gas properties	$	206,953		(1)	$	—			$	82,814		(2)
	Non-cash impairment of unproved oil and gas properties	19,598			(3)	37,348			(4)	17,464			(5)
	Dry hole costs	1,124				21,012				13,391
	Abandonment expense	10,723				9,509				3,930
	Total non-cash impairment, dry hole costs and abandonment expense	$	238,398			$	67,869			$	117,599
	-1	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2013 related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
	-2	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2011 related to properties within the Powder River and Wind River Basins. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.
	-3	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2013 was comprised of $17.1 million related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value and $2.5 million related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
	-4	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2012 related to certain unproved oil and gas properties within exploration projects primarily as a result of unfavorable natural gas exploratory results, unfavorable market conditions or no future plans to evaluate the remaining acreage.
	-5	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2011 related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value.
	The provision for DD&A of oil and gas properties is calculated on a field-by-field basis using the unit-of-production method. Natural gas is converted to barrel of oil equivalents, Boe, at the standard rate of six Mcf to one barrel. Estimated future dismantlement, restoration and abandonment costs, which are net of estimated salvage values, are taken into consideration by this calculation.
	Accounts Payable and Accrued Liabilities. Accounts payable and accrued liabilities are comprised of the following:
		As of December 31,
		2013				2012
		(in thousands)
	Accrued drilling, completion and facility costs	$	54,750			$	42,094
	Accrued lease operating, gathering, transportation and processing expenses	17,317				16,862
Accrued general and administrative expenses	14,605				13,054
Trade payables and other	29,256				53,007
Total accounts payable and accrued liabilities	$	115,928			$	125,017
Environmental Liabilities. Environmental expenditures that relate to an existing condition caused by past operations and that do not contribute to current or future revenue generation are expensed. Environmental liabilities are accrued when environmental assessments and/or clean-ups are probable, and the costs can be reasonably estimated.
Revenue Recognition. The Company records revenues from the sales of oil, natural gas and NGLs when delivery to the purchaser has occurred. The Company uses the sales method to account for gas and NGL imbalances. Under this method, revenue is recorded on the basis of gas and NGLs actually sold by the Company. In addition, the Company records revenues for its share of gas and NGLs sold by other owners that cannot be volumetrically balanced in the future due to insufficient remaining reserves. The Company also reduces revenues for other owners’ gas and NGLs sold by the Company that cannot be volumetrically balanced in the future due to insufficient remaining reserves. The Company’s remaining over- and under- produced gas and NGLs balancing positions are considered in the Company’s proved oil, gas and NGL reserves. Imbalances at December 31, 2013 and 2012 were not material.
Derivative Instruments and Hedging Activities. The Company periodically uses derivative financial instruments to achieve a more predictable cash flow from its oil, natural gas and NGL sales by reducing its exposure to price fluctuations. Derivative instruments are recorded at fair market value and are included in the Consolidated Balance Sheets as assets or liabilities.
Income Taxes. Income taxes are provided for the tax effects of transactions reported in the financial statements and consist of taxes currently payable plus deferred income taxes related to certain income and expenses recognized in different periods for financial and income tax reporting purposes. Deferred income tax assets and liabilities represent the future tax return consequences of those differences, which will either be taxable or deductible when assets are recovered or liabilities are settled. Deferred income taxes also include tax credits and net operating losses that are available to offset future income taxes. Deferred income taxes are measured by applying currently enacted tax rates.
The Company accounts for uncertainty in income taxes for tax positions taken or expected to be taken in a tax return. Only tax positions that meet the more-likely-than-not recognition threshold are recognized.
Earnings/Loss Per Share. Basic net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding during each period. Diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding and other dilutive securities. Potentially dilutive securities for the diluted net income per common share calculations consist of nonvested equity shares of common stock, in-the-money outstanding stock options to purchase the Company’s common stock and shares into which the Convertible Notes are convertible. No potential common shares are included in the computation of any diluted per share amount when a net loss exists, as was the case for the year ended December 31, 2013.
In satisfaction of its obligation upon conversion of the Convertible Notes, the Company may elect to deliver, at its option, cash, shares of its common stock or a combination of cash and shares of its common stock. As of December 31, 2013, the Company expected to settle the remaining Convertible Notes in cash. Therefore, the treasury stock method was used to measure the potentially dilutive impact of shares associated with that remaining conversion feature. The Company has the right at any time with at least 30 days’ notice to call the Convertible Notes and the holders have the right to require the Company to purchase the notes on March 20, 2015, March 20, 2018 and March 20, 2023. The Convertible Notes have not been dilutive since their issuance in March 2008 and, therefore, did not impact the diluted net income (loss) per common share calculation for the years ended December 31, 2012 and 2011. The diluted net income (loss) per common share excludes the anti-dilutive effect of 3,162,436 and 115,215 shares of stock options and nonvested equity shares of common stock for the years ended December 31, 2012 and 2011, respectively.
The following table sets forth the calculation of basic and diluted net income (loss) per share:
	Year Ended December 31,
	2013				2012				2011
	(in thousands, except per share amounts)
Net income (loss)	$	(192,733	)		$	582			$	30,707
Basic weighted-average common shares outstanding in period	47,497				47,195				46,536
Add dilutive effects of stock options and nonvested equity shares of common stock	—				159				701
Diluted weighted-average common shares outstanding in period	47,497				47,354				47,237
Basic net income (loss) per common share	$	(4.06	)		$	0.01			$	0.66
Diluted net income (loss) per common share	$	(4.06	)		$	0.01			$	0.65
Industry Segment and Geographic Information. The Company operates in one industry segment, which is the development and production of crude oil, natural gas and NGLs, and all of the Company’s operations are conducted in the continental United States. Consequently, the Company currently reports as a single industry segment.
New Accounting Pronouncements. In January 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2013-1, Balance Sheet: Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities, which amended FASB Accounting Standards Codification (“ASC”) Topic 210, Balance Sheet. The main objective in developing this update was to address implementation issues about the scope of ASU 2011-11, Balance Sheet: Disclosures about Offsetting Assets and Liabilities. The amendments clarify that the scope of ASU 2011-11 applies to derivatives accounted for in accordance with Topic 815, Derivatives and Hedging, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with ASC 210-20-45 or ASC 815-10-45 or subject to an enforceable master netting arrangement or similar agreement. This provision is effective for fiscal years beginning on or after January 1, 2013. Adoption of this update did not have a material impact on the Company’s disclosures or financial statements.
In February 2013, the FASB issued ASU 2013-2, Comprehensive Income: Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, which amended ASC Topic 220, Comprehensive Income. The objective of this update was to improve the reporting of reclassifications out of accumulated other comprehensive income. The amendment did not change the requirements for reporting net income or other comprehensive income in financial statements. However, the amendment required an entity to provide information about the amounts reclassified out of accumulated other comprehensive income by component. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income but only if the amount reclassified is required under U.S. GAAP to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures required under U.S. GAAP that provide additional detail about those amounts. This provision is effective for interim and annual periods beginning after December 15, 2012. Adoption of this update did not have a material impact on the Company’s disclosures or financial statements.
In July 2013, the FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. The objective of ASU 2013-11 is to provide guidance on financial statement presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists.  ASU 2013-11 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. The adoption of this standard will not have an impact on the Company’s consolidated financial statements.

Supplemental_Disclosures_of_Ca

Supplemental Disclosures of Cash Flow Information	12 Months Ended
	Dec. 31, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Disclosures of Cash Flow Information	'
	Supplemental Disclosures of Cash Flow Information
	Supplemental cash flow information is as follows:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Cash paid for interest, net of amount capitalized	$	94,205		$	83,718		$	36,504
	Cash paid for income taxes	1,163			10			(8,128		)
	Supplemental disclosures of non-cash investing and financing activities:
	Current liabilities	75,340			49,598			66,257
	Net increase (decrease) in asset retirement obligations	(6,996		)	(25,236		)	13,185
	Treasury stock acquired for employee stock option exercises	—			—			592
	Retirement of treasury stock	1,778			2,513			4,436

Divestitures

Divestitures	12 Months Ended
	Dec. 31, 2013
Discontinued Operations and Disposal Groups [Abstract]	'
Divestitures	'
	Divestitures
	On December 10, 2013, the Company completed the sale of its West Tavaputs natural gas assets in the Uinta Basin (the “West Tavaputs Divestiture”). The Company received $309.4 million in cash proceeds, after initial closing adjustments. The divestiture proceeds are subject to various purchase price adjustments incurred in the normal course of business and will be finalized during 2014. The Company recognized an impairment loss of $209.5 million in the year ended December 31, 2013 related to these assets. The carrying amounts by major asset class within the disposal group are summarized below:
		As of December 10, 2013
		(in thousands)
	Assets
	Proved properties	$	1,058,319
	Unproved properties	10,598
	Furniture, equipment and other	4,380
	Accumulated depreciation, depletion, amortization and impairment	(706,810		)
	Other Assets	1,533
	Total assets	$	368,020
	Liabilities
	Asset retirement obligation	$	13,471
	Lease financing obligation	45,190
	Total liabilities	$	58,661
	Net assets	$	309,359
	On December 31, 2012, the Company completed the sale of natural gas assets including 100% of its Wind River Basin, 100% of the Powder River Basin coalbed methane assets, and a non-operating working interest in its Gibson Gulch-Piceance Basin development property (the “2012 Divestiture”). The Company received $325.3 million in cash proceeds and recognized a $4.5 million pre-tax loss included in other operating revenues for the year ended December 31, 2012. Due to final post-closing adjustments, the Company recognized an additional $3.1 million pre-tax loss included in other operating revenues for the year ended December 31, 2013.

LongTerm_Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Long-Term Debt	'
	Long-Term Debt
	The Company’s outstanding debt is summarized below:
			As of December 31, 2013								As of December 31, 2012
		Maturity Date	Principal			Unamortized			Carrying		Principal		Unamortized			Carrying
						Discount			Amount				Discount			Amount
			(in thousands)
	Amended Credit Facility (1)	October 31, 2016	$	115,000		$	—		$	115,000	$	—	$	—		$	—
	9.875% Senior Notes (2)	July 15, 2016	—			—			—		250,000		(7,209		)	242,791
	Convertible Notes (3)	March 15, 2028 (4)	25,344			—			25,344		25,344		—			25,344
	7.625% Senior Notes (5)	October 1, 2019	400,000			—			400,000		400,000		—			400,000
	7.0% Senior Notes (6)	October 15, 2022	400,000			—			400,000		400,000		—			400,000
	Lease Financing Obligation (7)	August 10, 2020	43,329			—			43,329		97,596		—			97,596
	Total Debt		$	983,673		$	—		$	983,673	$	1,172,940	$	(7,209	)	$	1,165,731
	Less: Current Portion of Long-Term Debt		4,591			—			4,591		9,077		—			9,077
	Total Long-Term Debt		$	979,082		$	—		$	979,082	$	1,163,863	$	(7,209	)	$	1,156,654
	-1	The recorded value of the Amended Credit Facility approximates its fair value due to its floating rate structure and on financing terms currently available to the Company.
	-2	The aggregate estimated fair value of the 9.875% Senior Notes was $271.9 million as of December 31, 2012 based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013.
	-3	The aggregate estimated fair value of the Convertible Notes was approximately $25.1 million and $25.3 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.
	-4	The Company has the right at any time, with at least 30 days’ notice, to call the Convertible Notes, and the holders have the right to require the Company to purchase the notes on each of March 20, 2015, March 20, 2018 and March 20, 2023.
	-5	The aggregate estimated fair value of the 7.625% Senior Notes was approximately $430.2 million and $435.0 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.
	-6	The aggregate estimated fair value of the 7.0% Senior Notes was approximately $417.0 million and $413.8 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.
	-7	The aggregate estimated fair value of the Lease Financing Obligation was approximately $41.7 million and $97.7 million as of December 31, 2013 and 2012, respectively. Because there is no active, public market for the Lease Financing Obligation, the aggregate estimated fair value was based on market-based parameters of comparable term secured financing instruments.
	Amended Credit Facility
	The Company’s Amended Credit Facility has a maturity date of October 31, 2016 and current commitments and borrowing base of $625.0 million. Interest rates are LIBOR plus applicable margins of 1.5% to 2.5% or ABR plus 0.5% to 1.5% and the commitment fee is between 0.375% to 0.5% based on borrowing base utilization. The average annual interest rates incurred on the Amended Credit Facility were 2.0% and 2.2% for the years ended December 31, 2013 and 2012, respectively.
	The borrowing base is required to be re-determined twice per year. Our borrowing base is dependent on our proved reserves and was, as of December 31, 2013, $625.0 million based on our June 30, 2013 proved reserves, adjusted for the sale of our West Tavaputs properties and our hedge position. Our borrowing capacity is reduced by a $26.0 million letter of credit. Future semi-annual borrowing bases under our Amended Credit Facility will be computed based on proved oil, natural gas and NGL reserves, hedge positions and estimated future cash flows from those reserves, as well as any other outstanding debt of the Company.
	The Amended Credit Facility also contains certain financial covenants. The Company is currently in compliance with all financial covenants and has complied with all financial covenants since issuance. As of December 31, 2013, the Company had $115.0 million outstanding under the Amended Credit Facility. As credit support for future payment under a contractual obligation, a $26.0 million letter of credit has been issued under the Amended Credit Facility, which reduces the current available borrowing capacity of the Amended Credit Facility to $484.0 million.
	9.875% Senior Notes Due 2016
	On July 15, 2013, the Company redeemed the entire outstanding $250.0 million principal amount of 9.875% Senior Notes for a redemption price of 104.938% of the principal amount of the notes, or $262.3 million. Unamortized debt discount and deferred financing costs related to the notes resulted in a loss upon settlement of $21.5 million for the year ended December 31, 2013.
	5% Convertible Senior Notes Due 2028
	On March 12, 2008, the Company issued $172.5 million aggregate principal amount of Convertible Notes. On March 20, 2012, $147.2 million of the outstanding principal amount, or approximately 85% of the outstanding Convertible Notes, were put to the Company and redeemed by the Company at par. The Company settled the notes in cash. After the redemption, $25.3 million aggregate principal amount of the Convertible Notes was outstanding. The Convertible Notes mature on March 15, 2028, unless earlier converted, redeemed or purchased by the Company. The Convertible Notes are senior unsecured obligations and rank equal in right of payment to all of the Company’s existing and future senior unsecured indebtedness, are senior in right of payment to all of the Company’s future subordinated indebtedness, and are effectively subordinated to all of the Company’s secured indebtedness with respect to the collateral securing such indebtedness. The Convertible Notes are structurally subordinated to all present and future secured and unsecured debt and other obligations of the Company’s subsidiaries. The Convertible Notes are fully and unconditionally guaranteed by the subsidiaries that guarantee the Company’s indebtedness under the Amended Credit Facility, the 7.625% Senior Notes and the 7.0% Senior Notes.
	The Convertible Notes bear interest at a rate of 5% per annum, payable semi-annually in arrears on March 15 and September 15 of each year. Holders of the remaining Convertible Notes may require the Company to purchase all or a portion of their Convertible Notes for cash on each of March 20, 2015, March 20, 2018 and March 20, 2023 at a purchase price equal to 100% of the principal amount of the Convertible Notes to be repurchased, plus accrued and unpaid interest, if any, up to but excluding the applicable purchase date. The Company has the right at any time with at least 30 days’ notice to call the Convertible Notes.
	7.625% Senior Notes Due 2019
	On September 27, 2011, the Company issued $400.0 million in principal amount of 7.625% Senior Notes due 2019 at par. The 7.625% Senior Notes mature on October 1, 2019. Interest is payable in arrears semi-annually on April 1 and October 1 beginning April 1, 2012. The 7.625% Senior Notes are senior unsecured obligations of the Company and rank equal in right of payment with all of the Company’s other existing and future senior unsecured indebtedness, including the Company’s Convertible Notes and 7.0% Senior Notes. The 7.625% Senior Notes are fully and unconditionally guaranteed by the subsidiaries that guarantee the Company’s indebtedness under the Amended Credit Facility, the Convertible Notes and the 7.0% Senior Notes. The 7.625% Senior Notes include certain covenants that limit the Company’s ability to incur additional indebtedness, make restricted payments, create liens or sell assets and that prohibit the Company from paying dividends. The Company is currently in compliance with all financial covenants and has complied with all financial covenants since issuance. The 7.625% Senior Notes are redeemable at the Company’s option at a redemption price of 103.813% of the principal amount of the notes on October 1, 2015.
	7.0% Senior Notes Due 2022
	On March 12, 2012, the Company issued $400.0 million in aggregate principal amount of 7.0% Senior Notes due 2022 at par. The 7.0% Senior Notes mature on October 15, 2022. Interest is payable in arrears semi-annually on April 15 and October 15 of each year. The 7.0% Senior Notes are senior unsecured obligations and rank equal in right of payment with all of the Company’s other existing and future senior unsecured indebtedness, including the Company’s Convertible Notes and 7.625% Senior Notes. The 7.0% Senior Notes are redeemable at the Company's option on October 15, 2017 at a redemption price of 103.5% of the principal amount of the notes. The 7.0% Senior Notes are fully and unconditionally guaranteed by the subsidiaries that guarantee the Company’s indebtedness under the Amended Credit Facility, the Convertible Notes and the 7.625% Senior Notes. The 7.0% Senior Notes include certain covenants that limit the Company’s ability to incur additional indebtedness, make restricted payments, create liens or sell assets and that prohibit the Company from paying dividends. The Company is currently in compliance with all financial covenants and has complied with all financial covenants since issuance.
	Lease Financing Obligation Due 2020
	On July 23, 2012, the Company entered into the Lease Financing Obligation, whereby the Company received $100.8 million through the sale and subsequent leaseback of existing compressors and related facilities owned by the Company. The Lease Financing Obligation expires on August 10, 2020, and the Company has the option to purchase the equipment at the end of the lease term for the then current fair market value. The Lease Financing Obligation also contains an early buyout option where the Company may purchase the equipment for $36.6 million on February 10, 2019. The lease payments related to the equipment are recognized as principal and interest expense based on a weighted average implicit interest rate of 3.3%. See Note 13 for discussion of aggregate minimum future lease payments. As part of the West Tavaputs Divestiture, the purchaser assumed approximately 51% of the Lease Financing Obligation, including the buy out option, leaving the Company with a balance of $43.3 million at December 31, 2013.
	The following table summarizes, for the periods indicated, the cash or accrued portion of interest expense related to the Amended Credit Facility, 9.875% Senior Notes, Convertible Notes, 7.625% Senior Notes, 7.0% Senior Notes and the Lease Financing Obligation along with the non-cash portion resulting from the amortization of the debt discount and transaction costs through interest expense:
		As of December 31,
		2013			2012			2011
		(in thousands)
	Amended Credit Facility (1)
	Cash interest	$	6,802		$	5,652		$	5,432
	Non-cash interest	2,342			2,342			2,922
	9.875% Senior Notes (2)
	Cash interest	$	13,373		$	24,688		$	24,688
	Non-cash interest	1,361			2,571			2,485
	Convertible Notes (3)
	Cash interest	$	1,267		$	2,909		$	8,625
	Non-cash interest	6			1,771			7,548
	7.625% Senior Notes (4)
	Cash interest	$	30,500		$	30,500		$	7,964
	Non-cash interest	1,070			1,066			332
	7.0% Senior Notes (5)
	Cash interest	$	28,000		$	22,400		$	—
	Non-cash interest	795			659			—
	Lease Financing Obligation (6)
	Cash interest	$	2,852		$	1,353		$	—
	Non-cash interest	30			15			—
	-1	Cash interest includes amounts related to interest and commitment fees paid on the Amended Credit Facility and participation and fronting fees paid on the letter of credit.
	-2	The stated interest rate for the 9.875% Senior Notes was 9.875% per annum with an effective interest rate of 11.2% per annum. The Company redeemed the 9.875% Senior Notes in full on July 15, 2013.
	-3	The stated interest rate for the Convertible Notes is 5% per annum. The effective interest rate of the Convertible Notes includes amortization of the debt discount, which represented the fair value of the equity conversion feature at the time of issue. The stated interest rate of 5% on the Convertible Notes will is the effective interest rate of the $25.3 million remaining principal balance, as the related debt discount was fully amortized as of March 31, 2012.
	-4	The stated interest rate for the 7.625% Senior Notes is 7.625% per annum with an effective interest rate of 8.0% per annum.
-5	The stated interest rate for the 7.0% Senior Notes is 7.0% per annum with an effective interest rate of 7.2% per annum.
-6	The effective interest rate for the Lease Financing Obligation is 3.3% per annum.

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Asset Retirement Obligations	'
	Asset Retirement Obligations
	A reconciliation of the Company’s asset retirement obligations for the year ended December 31, 2013, 2012 and 2011 is as follows:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Beginning of period	$	47,616		$	69,302		$	53,079
	Liabilities incurred	2,359			4,046			13,186
	Liabilities settled	(1,096		)	(871		)	(1,046		)
	Disposition of properties	(13,543		)	(33,560		)	—
	Accretion expense	3,481			4,421			4,083
	Revisions to estimate	4,188			4,278			—
	End of period	$	43,005		$	47,616		$	69,302
	Less: Current asset retirement obligations	3,805			1,566			715
	Long-term asset retirement obligations	$	39,200		$	46,050		$	68,587

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Assets and Liabilities Measured on a Recurring Basis
	The Company’s financial instruments, including cash and cash equivalents, accounts and notes receivable and accounts payable are carried at cost, which approximates fair value due to the short-term maturity of these instruments. The recorded value of the Amended Credit Facility, as discussed in Note 5, approximates its fair value due to its floating rate structure based on the LIBOR spread and the Company's borrowing base utilization.
	Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). The Company utilizes a mid-market pricing convention (the mid-point price between bid and ask prices) for valuation as a practical expedient for assigning fair value. The Company uses market data or assumptions that market participants would use in pricing the asset or liability, including assumptions about risk. These inputs can be readily observable, market corroborated or generally unobservable. The Company primarily applies the market and income approaches for recurring fair value measurements and utilizes the best available information. Given the Company’s historical market transactions, its markets and instruments are fairly liquid. Therefore, the Company has been able to classify fair value balances based on the observability of those inputs. A fair value hierarchy was established that prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements).
	Level 1 – Quoted prices are available in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 1 primarily consists of financial instruments such as exchange-traded derivatives, listed securities and U.S. government treasury securities.
	Level 2 – Pricing inputs are other than quoted prices in active markets included in Level 1, which are either directly or indirectly observable as of the reporting date. Level 2 includes those financial instruments that are valued using models or other valuation methodologies. These models are primarily industry-standard models that consider various assumptions, including quoted forward prices for commodities, time value, volatility factors and current market and contractual prices for the underlying instruments, as well as other relevant economic measures. Substantially all of these assumptions are observable in the marketplace throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace. Instruments in this category include non-exchange-traded derivatives such as over-the-counter forwards and options.
	Level 3 – Pricing inputs include significant inputs that are generally less observable than objective sources. These inputs may be used with internally developed methodologies that result in management’s best estimate of fair value. At each balance sheet date, the Company performs an analysis of all applicable instruments and includes in Level 3 all of those whose fair value is based on significant unobservable inputs.
	The following tables set forth by level within the fair value hierarchy the Company’s financial assets and financial liabilities that were measured at fair value on a recurring basis. Assets and liabilities are classified in their entirety 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 assets and liabilities and their placement within the fair value hierarchy levels.
		As of December 31, 2013
		Level 1		Level 2		Level 3		Total
		(in thousands)
	Assets
	Deferred Compensation Plan	$	941	$	—	$	—	$	941
	Cash Equivalents - Money Market Funds	53		—		—		53
	Commodity Derivatives	—		11,483		—		11,483
	Liabilities
	Commodity Derivatives	$	—	$	14,771	$	—	$	14,771
		As of December 31, 2012
		Level 1		Level 2		Level 3		Total
		(in thousands)
	Assets
	Deferred Compensation Plan	$	966	$	—	$	—	$	966
	Cash Equivalents - Money Market Funds	53		—		—		53
	Commodity Derivatives	—		40,432		—		40,432
	Liabilities
	Commodity Derivatives	$	—	$	7,875	$	—	$	7,875
	All fair values reflected in the table above and on the Consolidated Balance Sheets have been adjusted for non-performance risk. For applicable financial assets carried at fair value, the credit standing of the counterparties is analyzed and factored into the fair value measurement of those assets. In addition, the fair value measurement of a liability has been adjusted to reflect the nonperformance risk of the Company. The following methods and assumptions were used to estimate the fair values of the assets and liabilities in the table above.
	Level 1 Fair Value Measurements – The Company maintains a non-qualified deferred compensation plan (as discussed in more detail in Note 11) which allows certain management employees to defer receipt of a portion of their compensation. The Company maintains assets for the deferred compensation plan in a rabbi trust. The assets of the rabbi trust are invested in publicly traded mutual funds and are recorded in prepayments and other current assets and deferred financing costs and other noncurrent assets on the Consolidated Balance Sheets. The Company also has highly liquid short term investments in money market funds. The deferred compensation plan financial assets are reported at fair value based on active market quotes, which represent Level 1 inputs. The money market fund investments are recorded at carrying value, which approximates fair value, and represents Level 1 inputs. The fair values of the Company’s fixed rate 7.625% Senior Notes and 7.0% Senior Notes totaled $847.2 million as of December 31, 2013. The fair values of the Company’s fixed rate 9.875% Senior Notes, 7.625% Senior Notes and 7.0% Senior Notes totaled $1,120.7 million as of December 31, 2012. The fair values of the Company's fixed rate Senior Notes are based on active market quotes, which represent Level 1 inputs.
	Level 2 Fair Value Measurements – The fair value of oil, natural gas and NGL swaps and forwards are estimated using a combined income and market valuation methodology with a mid-market pricing convention based upon forward commodity price and volatility curves. The curves are obtained from independent pricing services reflecting broker market quotes. The Company did not make any adjustments to the obtained curves. The pricing services publish observable market information from multiple brokers and exchanges. No proprietary models are used by the pricing services for the inputs. The Company utilized the counterparties’ valuations to assess the reasonableness of the Company’s valuations.
	There is no active, public market for the Company’s Amended Credit Facility, Convertible Notes or Lease Financing Obligation. The Amended Credit Facility balance of $115.0 million as of December 31, 2013 approximates its fair value due to its floating rate structure. The Convertible Notes fair value of $25.1 million and $25.3 million as of December 31, 2013 and 2012, respectively, are measured based on market-based parameters of the various components of the Convertible Notes and over the counter trades. The Lease Financing Obligation fair values of $41.7 million and $97.7 million as of December 31, 2013 and 2012, respectively, are measured based on market-based parameters of comparable term secured financing instruments. The fair value measurements for the Amended Credit Facility, Convertible Notes and Lease Financing Obligation represent Level 2 inputs.
	Level 3 Fair Value Measurements – As of December 31, 2013 and 2012, the Company did not have assets or liabilities that were measured on a recurring basis classified under a Level 3 fair value hierarchy.
	Assets and Liabilities Measured on a Non-recurring Basis
	The Company utilizes fair value on a non-recurring basis to perform impairment tests on its property and equipment when required. During the year ended December 31, 2013, the Company recorded impairment charges of  $226.6 million on proved and unproved oil and gas properties. Included in the total impairment charge of $226.6 million was $209.5 million of impairment charges related to the West Tavaputs area of the Uinta Basin for which the Company utilized third party purchase offers as the basis for determining fair value. This property was sold in December 2013. The inputs used to determine such fair value for other non-recurring impairment tests are primarily based upon internally developed cash flow models as well as available external market data and would generally be classified within Level 3.
				Fair Value Measurements Using
		Net Carrying Value as of December 31, 2013		Level 1		Level 2		Level 3
		(in thousands)
	Proved property impairments (1)	$	1,937,913	$	—	$	—	$	206,953
	Unproved property impairments (1)	246,270		—		—		19,598
	(1) See Note 2 for additional details on impairment expense recognized.
				Fair Value Measurements Using
		Net Carrying Value as of December 31, 2012		Level 1		Level 2		Level 3
		(in thousands)
	Proved property impairments (1)	$	2,179,171	$	—	$	—	$	—
	Unproved property impairments (1)	405,808		—		—		37,348
	(1) See Note 2 for additional details on impairment expense recognized.
	The Company also applied fair value accounting guidance to measure the assets and liabilities in the 2012 Divestiture. The fair values of these items were primarily determined using the present value of estimated future cash inflows and outflows. Because of the unobservable nature of these inputs, they are classified within Level 3. See Note 4 for additional discussion of the 2012 Divestiture. Additionally, the Company uses fair value to determine the value of its asset retirement obligations. The inputs used to determine such fair value are primarily based upon costs incurred historically for similar work, as well as estimates from independent third parties for costs that would be incurred to restore leased property to the contractually stipulated condition and would generally be classified within Level 3.

Derivative_Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments	'
	Derivative Instruments
	The Company uses financial derivative instruments as part of its price risk management program to achieve a more predictable cash flow from its production revenues by reducing its exposure to commodity price fluctuations. The Company has entered into financial commodity swap contracts related to the sale of a portion of the Company’s production. The Company does not enter into derivative instruments for speculative or trading purposes.
	In addition to financial contracts, the Company at times may be party to various physical commodity contracts for the sale of oil, natural gas and NGLs that have varying terms and pricing provisions. These physical commodity contracts qualify for the normal purchase and normal sale exception and, therefore, are not subject to hedge or mark-to-market accounting. The financial impact of physical commodity contracts is included in oil, natural gas and NGL production revenues at the time of settlement.
	All derivative instruments, other than those that meet the normal purchase and normal sale exception, as mentioned above, are recorded at fair value and included on the Consolidated Balance Sheets as assets or liabilities. The following table summarizes the location, as well as the gross and net fair value amounts of all derivative instruments presented on the Consolidated Balance Sheets as of the dates indicated.
		As of December 31, 2013
	Balance Sheet	Gross Amounts of				Gross Amounts				Net Amounts of Assets
		Recognized Assets				Offset in the Balance				Presented in the Balance
						Sheet				Sheet
						(in thousands)
	Derivative assets	$	8,259			$	(8,086	)	(1)	$	173
	Deferred financing costs and other noncurrent assets	3,224				(685		)	(1)	2,539			(2)
	Total derivative assets	$	11,483			$	(8,771	)		$	2,712
		Gross Amounts of				Gross Amounts				Net Amounts of Liabilities
		Recognized				Offset in the Balance				Presented in the Balance
		Liabilities				Sheet				Sheet
						(in thousands)
	Derivative liabilities	$	(14,074	)		$	8,086		(3)	$	(5,988	)
	Derivatives and other noncurrent liabilities	(697		)		685			(3)	(12		)	(4)
	Total derivative liabilities	$	(14,771	)		$	8,771			$	(6,000	)
		As of December 31, 2012
	Balance Sheet	Gross Amounts of				Gross Amounts				Net Amounts of Assets
		Recognized Assets				Offset in the Balance				Presented in the Balance
						Sheet				Sheet
						(in thousands)
	Derivative assets	$	34,828			$	(4,848	)	(1)	$	29,980
	Deferred financing costs and other noncurrent assets	5,604				(2,623		)	(1)	2,981			(2)
	Total derivative assets	$	40,432			$	(7,471	)		$	32,961
		Gross Amounts of				Gross Amounts				Net Amounts of Liabilities
		Recognized				Offset in the Balance				Presented in the Balance
		Liabilities				Sheet				Sheet
						(in thousands)
	Derivative liabilities	$	(4,848	)		$	4,848		(3)	$	—
	Derivatives and other noncurrent liabilities	(3,027		)		2,623			(3)	(404		)	(4)
	Total derivative liabilities	$	(7,875	)		$	7,471			$	(404	)
	-1	Amounts are netted against derivative asset balances with the same counterparty, and therefore, are presented as a net asset on the Consolidated Balance Sheets.
	-2	As of December 31, 2013 and 2012, this line item on the Consolidated Balance Sheets included $19.2 million and $26.8 million of deferred financing costs and other noncurrent assets, respectively.
	-3	Amounts are netted against derivative liability balances with the same counterparty, and therefore are presented as a net liability on the Consolidated Balance Sheets.
	-4	As of December 31, 2013 and 2012, this line item on the Consolidated Balance Sheets includes $3.5 million and $4.1 million of other noncurrent liabilities, respectively.
	The following table summarizes the cash flow hedge gains, net of tax, and their locations on the Consolidated Balance Sheets and Consolidated Statements of Operations for the periods indicated:
		Derivatives Qualifying as		Year Ended December 31,
		Cash Flow Hedges		2013				2012				2011
				(in thousands)
	Amount of Gain (Loss) Recognized in AOCI (1)	Commodity Hedges		$	—			$	—			$	70,636
	Amount of Gain (Loss) Reclassified from AOCI into Income (net of tax) (1)(2)	Commodity Hedges		$	4,663			$	50,712			$	62,421
	Amount of Gain (Loss) Recognized in Income on Ineffective Hedges	Commodity Hedges		$	—			$	—			$	1,026
	-1	Presented net of income tax expense of $2.8 million and $30.5 million and income tax benefit of $4.9 million for the years ended December 31, 2013, 2012 and 2011, respectively.
	-2	Gains reclassified from AOCI into income are included in the oil, gas and NGL production revenues in the Consolidated Statements of Operations.
	As of December 31, 2013, the Company had financial instruments in place to hedge the following volumes for the periods indicated:
		Year Ending December 31,
		2014			2015			2016
	Oil (Bbls)	3,211,400			1,348,700			91,000
	Natural Gas (MMbtu)	24,335,000			3,650,000			—
	Natural Gas Liquids (Bbls)	235,714			—			—
	The table below summarizes the commodity derivative gains and losses the Company recognized related to its oil, gas and NGL derivative instruments for the periods indicated:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Commodity derivative settlements on derivatives designated as cash flow hedges (1)	$	7,463			$	81,166			$	99,922
	Total commodity derivative gain (loss) (2)	(23,068		)		72,759				(14,263		)
	-1	Included in oil, gas and NGL production revenues in the Consolidated Statements of Operations.
	-2	Included in commodity derivative gain (loss) in the Consolidated Statements of Operations.
	The Company’s derivative financial instruments are generally executed with major financial or commodities trading institutions that expose the Company to market and credit risks and may, at times, be concentrated with certain counterparties or groups of counterparties. The Company had hedges in place with 9 different counterparties as of December 31, 2013. Although notional amounts are used to express the volume of these contracts, the amounts potentially subject to credit risk, in the event of non-performance by the counterparties, are substantially smaller. The creditworthiness of counterparties is subject to continual review by management, and the Company believes all of these institutions currently are acceptable credit risks. Full performance is anticipated, and the Company has no past due receivables from any of its counterparties.
	It is the Company’s policy to enter into derivative contracts with counterparties that are lenders in the Amended Credit Facility, affiliates of lenders in the Amended Credit Facility or potential lenders in the Amended Credit Facility. The Company’s derivative contracts are documented using an industry standard contract known as a Schedule to the Master Agreement and International Swaps and Derivative Association, Inc. (“ISDA”) Master Agreement or other contracts. Typical terms for these contracts include credit support requirements, cross default provisions, termination events and set-off provisions. The Company is not required to provide any credit support to its counterparties other than cross collateralization with the properties securing the Amended Credit Facility. The Company has set-off provisions in its derivative contracts with lenders under its Amended Credit Facility which, in the event of a counterparty default, allow the Company to set-off amounts owed to the defaulting counterparty under the Amended Credit Facility or other obligations against monies owed the Company under derivative contracts. Where the counterparty is not a lender under the Company’s Amended Credit Facility, it may not be able to set-off amounts owed by the Company under the Amended Credit Facility, even if such counterparty is an affiliate of a lender under such facility. The Company does not have any derivative balances that are offset by cash collateral.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The expense for income taxes consisted of the following for the periods indicated:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Current:
	Federal	$	(1,233	)	$	966		$	(18	)
	State	(352		)	886			—
	Foreign	2			1			2
	Deferred:
	Federal	(107,300		)	100			16,804
	State	(9,750		)	(317		)	884
	Total	$	(118,633	)	$	1,636		$	17,672
	Income tax expense differed from the amounts computed by applying the U.S. federal income tax rate of 35% to pretax income from continuing operations as a result of the following:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Income tax expense at the federal statutory rate	$	(108,978	)	$	777		$	16,932
	State income taxes, net of federal tax effect	(6,702		)	(269		)	1,223
	Incentive stock compensation	678			635			(545		)
	Nondeductible political contributions and lobbying costs	96			271			238
	Nondeductible officer compensation	138			—			—
	Other permanent items	52			26			84
	Deferred tax related to the changes in overall state tax rates	(3,851		)	310			(286		)
	Other, net	(66		)	(114		)	26
	Income tax expense	$	(118,633	)	$	1,636		$	17,672
	The tax effects of temporary differences that give rise to significant components of the deferred tax assets and deferred tax liabilities at December 31, 2013 and 2012 are presented below:
		As of December 31,
		2013			2012
		(in thousands)
	Current:
	Deferred tax assets (liabilities):
	Derivative instruments	$	(89	)	$	(13,108	)
	Accrued expenses	400			409
	Bad debt expense	8			122
	Prepaid expenses	(648		)	(776		)
	Other	130			(399		)
	Total current deferred tax assets (liabilities)	$	(199	)	$	(13,752	)
	Long-term:
	Deferred tax assets:
	Net operating loss carryforward	$	75,511		$	39,634
	Deferred offering costs	1,243			1,333
	Stock-based compensation	14,200			8,117
	Deferred rent	962			1,276
	Long-term derivative instruments	1,306			878
	Minimum tax credit carryforward	688			1,315
	Deferred compensation	999			379
	State tax credit carryfowards	5,871			4,646
	Production payment loan	3,839			8,374
	Financing obligation	16,227			36,776
	Other	222			—
	Less: Valuation allowance	(5,871		)	(4,646		)
	Total long-term deferred tax assets	115,197			98,082
	Deferred tax liabilities:
	Oil and gas properties	(276,523		)	(364,446		)
	Total long-term deferred tax liabilities	(276,523		)	(364,446		)
	Net long-term deferred tax liabilities	$	(161,326	)	$	(266,364	)
	At December 31, 2013, the Company had approximately $218.0 million of federal tax net operating loss carryforwards that expire through 2033. The Company has a federal alternative minimum tax credit carryforward of $0.7 million, which has no expiration date.
	In assessing the realizability of deferred tax assets, management must consider whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Management considers all available evidence (both positive and negative) in determining whether a valuation allowance is required. Such evidence includes the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment, and judgment is required in considering the relative weight of negative and positive evidence. The Company continues to monitor facts and circumstances in the reassessment of the likelihood that operating loss carryforwards, credits and other deferred tax assets will be utilized prior to their expiration. As a result, it may be determined that a deferred tax asset valuation allowance should be established. Any increases or decreases in a deferred tax asset valuation allowance would impact net income through offsetting changes in income tax expense. At December 31, 2013, the Company had approximately $5.9 million of state income tax credit carryforwards that begin expiring in 2017. A valuation allowance against these credits was recorded in 2011. It is currently estimated that the state income tax credits will not be utilized because the Company does not project to have sufficient future taxable income in the appropriate jurisdictions, and therefore the valuation allowance on the full amount of the credit carryforwards will remain.
	At December 31, 2013, the Consolidated Balance Sheet reflected a net deferred tax liability of $161.5 million, of which $0.4 million pertains to the tax effects reflected in AOCI.
	The Company accounts for uncertainty in income taxes for tax positions taken or expected to be taken in a tax return. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained upon examination by the taxing authorities, based on the technical merits.
	The Company did not have any additions, reductions or settlements of unrecognized tax benefits in the years ended December 2013, 2012 and 2011.
	In 2013, the Company generated no uncertain tax positions. The Company anticipates that no uncertain tax positions will be recognized within the next 12-month period. The Company’s policy is to classify accrued penalties and interest related to unrecognized tax benefits in the Company’s income tax provision. As of December 31, 2013, the Company did not have any accrued interest or penalties associated with any unrecognized tax benefits, nor was any interest expense recognized during the current year.
The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction and in various states. With few exceptions, the Company is subject to U.S. federal tax examination for years 2010 through 2013 and is subject to state tax examination for years 2009 through 2013.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Stockholders' Equity	'
	Stockholders' Equity
	Common and Preferred Stock. The Company’s authorized capital structure consists of 75,000,000 shares of preferred stock, par value $0.001 per share and 150,000,000 shares of common stock, par value $0.001 per share. In October 2004, 150,000 shares of $0.001 per share par value preferred stock were designated as Series A Junior Participating Preferred Stock, none of which are outstanding. The remainder of the authorized preferred stock is undesignated. There are no issued and outstanding shares of preferred stock.
	When issued, each share of Series A Junior Participating Preferred Stock will entitle the holder thereof to 1,000 votes on all matters submitted to a vote of the Company’s stockholders.
	Treasury Stock. The Company may occasionally acquire treasury stock, which is recorded at cost, in connection with the vesting and exercise of stock-based awards or for other reasons. As of December 31, 2013, all treasury stock held by the Company was retired.
	The following table reflects the activity in the Company’s common and treasury stock for the periods indicated:
		Year Ended December 31,
		2013			2012			2011
	Common Stock Outstanding:
	Shares at beginning of period	48,150,475			47,809,903			46,813,269
	Exercise of common stock options	259,699			36,560			836,833
	Shares issued for 401(k) plan	47,235			41,415			20,913
	Shares issued for directors' fees	52,081			12,973			7,636
	Shares issued for nonvested equity shares of common stock	1,081,259			454,666			353,716
	Shares retired or forfeited	(438,301	)		(205,042	)		(222,464	)
	Shares at end of period	49,152,448			48,150,475			47,809,903
	Treasury Stock:
	Shares at beginning of period	—			—			—
	Treasury stock acquired	96,880			92,393			113,715
	Treasury stock retired	(96,880	)		(92,393	)		(113,715	)
	Shares at end of period	—			—			—
	Accumulated Other Comprehensive Income. The components of accumulated other comprehensive income and related tax effects for the years ended December 31, 2011, 2012 and 2013 were as follows:
		Gross				Tax Effect				Net of Tax
		(in thousands)
	Accumulated other comprehensive income — December 31, 2010	$	76,613			$	(28,784	)		$	47,829
	Unrealized change in fair value of hedges	113,023				(42,387		)		70,636
	Reclassification adjustment for realized gains on hedges included in net income	(99,922		)		37,501				(62,421		)
	Accumulated other comprehensive income — December 31, 2011	$	89,714			$	(33,670	)		$	56,044
	Reclassification adjustment for realized gains on hedges included in net income	(81,170		)		30,458				(50,712		)
	Accumulated other comprehensive income — December 31, 2012	$	8,544			$	(3,212	)		$	5,332
	Reclassification adjustment for realized gains on hedges included in net income	(7,465		)		2,802				(4,663		)
	Accumulated other comprehensive income — December 31, 2013	$	1,079			$	(410	)		$	669

Equity_Incentive_Compensation_

Equity Incentive Compensation Plans and Other Employee Benefits	12 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Equity Incentive Compensation Plans and Other Employee Benefits	'
	Equity Incentive Compensation Plans and Other Employee Benefits
	The Company maintains various stock-based compensation plans and other employee benefit plans as discussed below. Stock-based compensation is measured at the grant date based on the value of the awards, and the fair value is recognized on a straight-line basis over the requisite service period (usually the vesting period).
	The following table presents the non-cash stock-based compensation related to equity awards for the periods indicated:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Common stock options	$	4,696			$	7,189			$	7,569
	Nonvested equity common stock	7,492				7,394				8,703
	Nonvested equity common stock units (1)	1,272				708				—
	Nonvested performance-based equity	2,174				1,079				3,124
	Total	$	15,634			$	16,370			$	19,396
	-1	Includes non-cash stock-based compensation related to director fees of $0.4 million and $0.2 million for the year ended December 31, 2013 and 2012, respectively.
	Unrecognized compensation cost as of December 31, 2013 was $19.0 million related to grants of nonvested stock options and nonvested equity shares of common stock that are expected to be recognized over a weighted-average period of 2.3 years.
	Stock Options and Nonvested Equity Shares. In May 2012, the Company’s stockholders approved and the Company adopted its 2012 Equity Incentive Plan (the “2012 Incentive Plan”). The purpose of the 2012 Incentive Plan is to enhance the Company’s ability to attract and retain officers, employees and directors and to provide such persons with an interest in the Company aligned with the interests of stockholders. The 2012 Incentive Plan provides for the grant of stock options (including incentive stock options and non-qualified stock options) and other awards, including performance units, performance shares, share awards, share units, restricted stock, cash incentive, and stock appreciation rights or SARs.
	The aggregate number of shares that the Company may issue under the 2012 Incentive Plan may not exceed 2,051,402 shares, subject to adjustment for future stock splits, stock dividends and similar changes in the Company’s capitalization. Shares underlying grants that expire without being exercised or are forfeited are available for grant under the 2012 Incentive Plan. The aggregate number of shares of common stock subject to options, stock appreciation rights, or performance-based awards granted to a participant during any calendar year may not exceed 500,000 shares, and the maximum amount payable to a participant during any calendar year with respect to performance-based or cash incentive awards that are not denominated in common stock or common stock equivalents may not exceed $5.0 million. The 2012 Incentive Plan provides that all awards granted under the 2012 Incentive Plan expire not more than 10 years from the grant date and have an exercise price of no less than the closing price of the Company’s common stock on the date of grant.
	Currently, the Company’s practice is to issue new shares upon stock option exercise. The Company does not expect to repurchase any shares in the open market or issue treasury shares to settle any such exercises. For the years ended December 31, 2013, 2012 and 2011, the Company did not pay cash to repurchase any stock option exercises.
	The fair value of each share-based option award under all of the Company’s plans is estimated on the date of grant using a Black-Scholes pricing model that incorporates the assumptions noted in the following table. Estimated expected volatilities were based upon historical volatility of the Company’s common stock. The Company does not expect to declare or pay dividends in the foreseeable future; thus, the Company used a 0% expected dividend yield, which is comparable to most of its peers in the industry. The expected terms range from 0.09 years to 6.0 years, or a weighted average of 4.3 years to 4.6 years, based on 25% of each grant’s vesting on each anniversary date and factoring in potential blackout dates, historic exercises and expectations of future employee behavior. The risk-free rate is based on the U.S. Treasury yield curve in effect on the date of grant and extrapolated to approximate the expected life of the award. The Company estimated a 4% to 10% annual compounded forfeiture rate for the years 2012 and 2011 based on historical employee turnover and actual forfeitures.
			2012			2011
	Weighted average volatility		51	%		55	%
	Expected dividend yield		—	%		—	%
	Weighted average expected term (in years)		4.3			4.5
	Weighted average risk-free rate		1.8	%		1.9	%
	A summary of share-based option activity under all the Company's plans as of December 31, 2013, and changes during the year then ended, is presented below:
		Shares			Weighted Average				Weighted Average		Aggregate
					Exercise Price				Remaining		Intrinsic Value
									Contractual Term
									(in years)
	Outstanding at January 1, 2013	3,020,485			$	32.4
	Granted	—			—
	Exercised	(259,699	)		24.51
	Forfeited or expired	(1,012,090	)		33.98
	Outstanding at December 31, 2013	1,748,696			32.66				1.47		$	1,239,464
	Vested and exercisable at December 31, 2013	1,310,201			$	33.37			1.96		$	1,041,448
	Expected to vest, at December 31, 2013 through the life of the options	1,718,579			28.84				2.59		5,679,748
	The per share weighted-average grant date fair value of options granted for the years ended December 31, 2012 and 2011 were $11.02 and $12.55, respectively. The total intrinsic value of options exercised for the years ended December 31, 2013, 2012 and 2011 were $0.5 million, $0.4 million and $10.0 million, respectively. With respect to stock option exercises, the Company received $6.4 million, $0.7 million, and $22.2 million for the years ended December 31, 2013, 2012 and 2011, respectively.
	A summary of the Company’s nonvested equity shares of common stock as of December 31, 2013, 2012 and 2011, and changes during the years then ended, is presented below:
		Year Ended December 31,
		2013							2012					2011
		Shares			Weighted				Shares			Weighted		Shares		Weighted
					Average							Average				Average
					Grant Date							Grant Date				Grant Date
					Fair							Fair				Fair
					Value							Value				Value
	Outstanding at January 1, 2013	579,188			$	31.02			639,628			$	35.12	603,521		$	30.94
	Granted	630,715			17.98				274,679			25.62		346,956		39.49
	Vested	(270,482	)		29.82				(241,736	)		34.61		(220,006	)	31.83
	Forfeited or expired	(183,303	)		24.87				(93,383	)		33.39		(90,843	)	32.03
	Outstanding at December 31, 2013	756,118			$	22.17			579,188			$	31.02	639,628		$	35.12
	Expected to vest, at December 31, through the life of the awards	661,224			$	22.34			503,412			$	31.08	578,131		$	34.94
	Equity common stock units were issued beginning on July 1, 2012 and will be converted to shares of common stock as they vest. As of December 31, 2013, equity common stock units have only been issued for payment of director fees. A summary of the Company’s nonvested equity share units of common stock as of December 31, 2013, 2012 and 2011, and changes during the years then ended, is presented in the table below:
		Year Ended December 31,
		2013							2012					2011
		Shares			Weighted				Shares			Weighted		Shares		Weighted
					Average							Average				Average
					Grant Date							Grant Date Fair				Grant Date Fair
					Fair							Value				Value
					Value
	Outstanding at January 1, 2013	49,185			$	18.5			—			$	—	—		$	—
	Granted (1)	56,464			22.33				58,983			18.83		—		—
	Vested (1)	(49,871	)		18.96				(9,798	)		20.51		—		—
	Forfeited or expired	—			—				—			—		—		—
	Outstanding at December 31, 2013	55,778			$	19.35			49,185			$	18.5	—		$	—
	The fair value of equity awards vested for the years ended December 31, 2013, 2012 and 2011 was $8.1 million, $8.6 million and $8.8 million, respectively.
Performance Share Programs
2010 Program. In February 2010, the Compensation Committee of the Board of Directors of the Company approved a performance share program (the “2010 Program”). Upon commencement of the 2010 Program and during each subsequent year of the 2010 Program through 2013, the Compensation Committee met to approve target and stretch goals for certain operational or financial metrics that are selected by the Compensation Committee for the upcoming year and to determine whether metrics for the prior year have been met. As new goals are established each year for the performance-based awards, a new grant date and a new fair value are created for financial reporting purposes for those shares that could potentially vest in the upcoming year. Compensation expense is recognized based upon an estimate of the extent to which the performance goals would be met. If such goals are not met, no compensation expense is recognized and any previously recognized compensation expense is reversed.
The 2010 Program has both performance-based and market-based goals. All compensation expense related to the market-based goals will be recognized if the requisite service period is fulfilled, even if the market condition is not achieved. Based on Company performance in 2011, 26.6% of the 2010 Program performance shares vested in February 2012. Accordingly, the Company recognized non-cash stock-based compensation of costs associated with those shares of $0.2 million and $2.4 million for the years ended December 31, 2012 and 2011, respectively. Based upon the Company’s performance in 2012, none of the 2010 Program performance shares vested in February 2013.
In February 2013, the Compensation Committee established vesting terms of the Company’s nonvested equity awards in the 2010 Program that are subject to a market performance-based vesting condition, which is based on the Company’s total shareholder return (“TSR”) ranking relative to a defined peer group’s individual TSRs (“Relative TSR”). In February 2013, 22,710 market-based nonvested equity shares of common stock became subject to a new grant date, and the fair value of the shares was remeasured at the grant date. All shares that remain unvested based on 2013 performance will expire in 2014. The fair value of the market-based awards is amortized ratably over the remaining requisite service period. All compensation expense related to the market-based awards will be recognized if the requisite service period is fulfilled, even if the market condition is not achieved. Based on the Company's performance in 2013, 19.8% of the 2010 Program performance shares will vest in February 2014. Accordingly, the Company recorded $0.1 million of non-cash stock-based compensation expense related to these awards for the year ended December 31, 2013.
In February 2013, the Compensation Committee approved the performance metrics used to measure potential vesting of the performance shares in the 2010 Program based on 2013 performance. For the year ended December 31, 2013, the performance goals consisted of the Company’s TSR ranking relative to a defined peer group’s individual TSR (weighted at 40%), the Company’s discretionary cash flow (weighted at 30%) and PV10 of proved oil, natural gas and NGL reserves (weighted at 30%). In February 2013, 86,223 performance-based nonvested equity shares of common stock in the 2010 Program became subject to a new grant date, and the fair value of the shares was remeasured at the grant date. All remaining unvested shares could potentially vest if all performance goals are met at the stretch level, and all shares that remain unvested based on 2013 performance will expire in 2014. All compensation expense related to the TSR metric will be recognized if the requisite service period is fulfilled, even if the market condition is not achieved. All compensation expense related to the discretionary cash flow metric and the proved oil, natural gas and NGL reserves metric will be based upon the number of shares expected to vest at the end of the one year period. The Company recorded $0.3 million of non-cash stock-based compensation expense related to these awards during the year ended December 31, 2013.
2012 Program. In March 2012, the Compensation Committee approved a new performance share program (the “2012 Program”). The performance-based awards contingently vest in May 2015, depending on the level at which the performance goals are achieved. The performance goals, which will be measured over the three year period ending December 31, 2014, consist of the Company’s TSR ranking relative to a defined peer group’s individual TSR (weighted at 33 1/3%), the percentage change in discretionary cash flow per debt adjusted share relative to a defined peer group’s percentage calculation (weighted at 33 1/3%) and percentage change in proved oil and natural gas reserves per debt adjusted share (weighted at 33 1/3%). fifty percent of the total award will vest for performance met at the threshold level, 100% will vest at the target level and 200% will vest at the stretch level. If the actual results for a metric are between the threshold and target levels or between the target and stretch levels, the vested number of shares will be adjusted on a prorated basis of the actual results compared to the threshold, target and stretch goals. If the threshold metrics are not met, no shares will vest. In any event, the total number of shares of common stock that could vest will not exceed 200% of the original number of performance shares granted. At the end of the three year vesting period, any shares that have not vested will be forfeited. A total of 179,798 shares were granted under this program during the year ended December 31, 2012. The Company recorded $0.2 million and $0.5 million of non-cash stock-based compensation expense related to these awards for the years ended December 31, 2013 and 2012, respectively.
2013 Program. In February 2013, the Compensation Committee approved a new performance share program (the “2013 Program”) pursuant to the 2012 Incentive Plan. The performance-based awards contingently vest in May 2016, depending on the level at which the performance goals are achieved. The performance goals, which will be measured over the three year period ending December 31, 2015, consist of the Company’s Relative TSR (weighted at 33 1/3%), the percentage change in discretionary cash flow per debt adjusted share relative to a defined peer group’s percentage calculation (“DCF per Debt Adjusted Share”) (weighted at 33 1/3%) and percentage change in proved oil, natural gas and NGL reserves per debt adjusted share (“Reserves per Debt Adjusted Share”) (weighted at 33 1/3%). The Relative TSR and DCF per Debt Adjusted Share goals will vest at 25% of the total award for performance met at the threshold level, 100% at the target level and 200% at the stretch level. The Reserves per Debt Adjusted Share goal will vest at 50% of the total award for performance met at the threshold level, 100% at the target level and 200% at the stretch level. If the actual results for a metric are between the threshold and target levels or between the target and stretch levels, the vested number of shares will be prorated based on the actual results compared to the threshold, target and stretch goals. If the threshold metrics are not met, no shares will vest. In any event, the total number of shares of common stock that could vest will not exceed 200% of the original number of performance shares granted. At the end of the three year vesting period, any shares that have not vested will be forfeited. A total of 450,544 shares were granted under this program during the year ended December 31, 2013. All compensation expense related to the Relative TSR metric will be recognized if the requisite service period is fulfilled, even if the market condition is not achieved. All compensation expense related to the DCF per Debt Adjusted Share metric and the Reserves per Debt Adjusted Share metric will be based upon the number of shares expected to vest at the end of the three year period. The Company recorded $1.6 million of non-cash stock-based compensation expense related to these awards for the year ended December 31, 2013.
A summary of the Company's non-vested performance-based equity shares of common stock as of December 31, 2013, 2012 and 2011, and changes during the years then ended, is presented below:
	Year Ended December 31,
	2013							2012					2011
	Shares			Weighted				Shares			Weighted		Shares		Weighted
				Average							Average				Average
				Grant Date							Grant Date				Grant Date
				Fair							Fair				Fair
				Value							Value				Value
Outstanding at January 1, 2013	291,606			$	26.85			195,630			$	33.36	287,932		$	31.76
Vested	—			—				(64,745	)		39.9		(81,156	)	32.1
Modified, performance goals revised (1)	(108,933	)		27.75				(121,191	)		39.9		(192,821	)	32.18
Modified, performance goals revised (1)	108,933			18.18				121,191			27.75		192,821		39.88
Granted	450,544			19.99				179,987			27.57		6,760		40.52
Forfeited or expired	(158,118	)		22.52				(19,266	)		33.82		(17,906	)	30.94
Outstanding at December 31, 2013	584,032			$	19.8			291,606			$	26.85	195,630		$	33.36
Expected to vest, at December 31, through the life of the awards	522,312			$	22.14			87,522			$	25.33	183,178		$	33.37
-1	As the Compensation Committee approved new performance metrics for the vesting of performance shares in the upcoming year, a new grant date was then created for any unvested awards that were granted in previous years, and a new fair value was established for financial reporting purposes.
The fair value of the performance-based shares vested in the years ended December 31, 2012 and 2011 was $2.6 million and $3.1 million, respectively.
Director Fees. The Company’s non-employee, or outside, directors, may elect to receive all or a portion of their annual retainer and meeting fees in the form of restricted stock units (“RSUs”), which are settled with shares of the Company’s common stock, issued pursuant to the Company’s 2012 Incentive Plan. After each quarter, RSUs with a value equal to the fees payable for that quarter, calculated using the closing price for the Company’s common stock on the last trading day of the quarter, will be delivered to each outside director who elected before that quarter to receive RSUs for payment of director fees. These nonvested RSUs will vest immediately at the end of the applicable quarter. Once vested, the RSUs will settle at the end of the applicable quarter or such later date elected by the director.
A summary of the Company’s directors’ fees and equity-based compensation for the years ended December 31, 2013, 2012 and 2011 is presented below:
	Year Ended December 31,
	2013				2012				2011
Director fees (shares)	16,151				12,973				7,636
Stock-based compensation (in thousands)	$	351			$	276			$	307
Other Employee Benefits-401(k) Savings Plan. The Company has an employee-directed 401(k) savings plan (the “401(k) Plan”) for all eligible employees over the age of 21. Under the 401(k) Plan, employees may make voluntary contributions based upon a percentage of their pretax income, subject to statutory limitations.
The Company matches 100% of each employee’s contribution, up to 6% of the employee’s pretax income, with 50% of the match made with the Company’s common stock. The Company’s cash and common stock contributions are fully vested upon the date of match, and employees can immediately sell the portion of the match made with the Company’s common stock. The Company made matching cash and common stock contributions of $1.9 million, $2.0 million and $1.7 million for the years ended December 31, 2013, 2012 and 2011, respectively.
Deferred Compensation Plan. In 2010, the Company adopted a non-qualified deferred compensation plan for certain employees and officers whose eligibility to participate in the plan was determined by the Compensation Committee of the Company’s Board of Directors. The Company makes matching cash contributions on behalf of eligible employees up to 6% of the employee’s cash compensation once the contribution limits are reached on the Company’s 401(k) Plan. All amounts deferred and matched under the plan vest immediately. Deferred compensation, including accumulated earnings on the participant-directed investment selections, is distributable in cash at participant-specified dates or upon retirement, death, disability, change in control or termination of employment.
The table below summarizes the activity in the plan during the years ended December 31, 2013 and 2012, and the Company’s ending deferred compensation liability as of December 31, 2013 and 2012:
	Year Ended December 31,
	2013				2012
	(in thousands)
Beginning deferred compensation liability balance	$	966			$	579
Employee contributions	206				262
Company matching contributions	115				189
Distributions	(441		)		(117		)
Participant earnings (losses)	95				53
Ending deferred compensation liability balance	$	941			$	966
Amount to be paid within one year	$	451			$	292
Remaining balance to be paid beyond one year	$	490			$	674
The Company has established a rabbi trust to offset the deferred compensation liability and protect the interests of the plan participants. The investments in the rabbi trust seek to offset the change in the value of the related liability. As a result, there is no expected impact on earnings or earnings per share from the changes in market value of the investment assets because the changes in market value of the trust assets are offset by changes in the value of the deferred compensation plan liability. The gains and losses from changes in fair value of the investments are included in interest and other income in the Consolidated Statements of Operations.
The following table represents the Company's activity in the investment assets held in the rabbi trust during the years ended December 31, 2013 and 2012:
	Year Ended December 31,
	2013				2012
	(in thousands)
Beginning investment balance	$	966			$	579
Investment purchases	321				451
Distributions	(441		)		(117		)
Earnings (losses)	95				53
Ending investment balance	$	941			$	966

Significant_Customers_and_Othe

Significant Customers and Other Concentrations	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Significant Customers and Other Concentrations	'
	Significant Customers and Other Concentrations
	Significant Customers. During 2013, one customer individually accounted for over 10% of the Company's oil, gas and NGL production revenues. During 2012, two customers individually accounted for over 10% of the Company’s oil, gas and NGL production revenues. During 2011, three customers individually accounted for over 10% of the Company’s oil, gas and NGL production revenues. Although diversified among many companies, collectability is dependent upon the financial stability of each individual company and is influenced by the general economic conditions of the industry. Management believes that the loss of any individual purchaser would not have a long-term material adverse impact on the financial position or results of operations of the Company.
	Concentrations of Market Risk. The future results of the Company’s oil and gas operations will be affected by the market prices of oil, natural gas and NGLs. A readily available market for oil, natural gas and NGLs in the future will depend on numerous factors beyond the control of the Company, including weather, imports, marketing of competitive fuels, proximity and capacity of oil and gas pipelines and other transportation facilities, any oversupply or undersupply of oil, gas and NGLs, the regulatory environment, the economic environment and other regional, national and international economic and political events, none of which can be predicted with certainty.
	The Company operates in the exploration, development and production phase of the oil and gas industry. Its receivables include amounts due from purchasers of oil and gas production and amounts due from joint venture partners for their respective portions of operating expenses and exploration and development costs. The Company believes that no single customer or joint venture partner exposes the Company to significant credit risk. While certain of these customers and joint venture partners are affected by periodic downturns in the economy in general or in their specific segment of the natural gas or oil industry, the Company believes that its level of credit-related losses due to such economic fluctuations has been and will continue to be immaterial to the Company’s results of operations in the long-term. Trade receivables are generally not collateralized. The Company analyzes customers’ and joint venture partners’ historical credit positions and payment histories prior to extending credit.
	Concentrations of Credit Risk. Derivative financial instruments that hedge the price of oil, natural gas and NGLs are generally executed with major financial or commodities trading institutions which expose the Company to market and credit risks and may, at times, be concentrated with certain counterparties or groups of counterparties. The Company’s policy is to execute financial derivatives only with major, creditworthy financial institutions. The Company has hedges in place with 9 different counterparties, of which all are lenders or affiliates of lenders in the Amended Credit Facility. It is the Company’s policy to enter into derivative contracts with counterparties that are lenders in the Amended Credit Facility, affiliates of lenders in the Amended Credit Facility or potential lenders in the Amended Credit Facility. The Company’s derivative contracts are documented using an industry standard contract known as an ISDA master agreement or other contracts.
	The creditworthiness of counterparties is subject to continuing review, and the Company believes all of these institutions currently are acceptable credit risks. Full performance is anticipated, and the Company has no past due receivables from any of its counterparties. Where the counterparty is a lender under the Amended Credit Facility, the counterparty risk is mitigated to the extent that the Company is indebted to such lender under the Amended Credit Facility.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	Lease Financing Obligation. The Company has a Lease Financing Obligation with Bank of America Leasing & Capital, LLC as the lead bank as discussed in Note 5. The aggregate undiscounted minimum future lease payments are presented below:
		As of December 31, 2013
		(in thousands)
	2014	$	5,942
	2015	5,942
	2016	5,942
	2017	5,942
	2018	5,942
	Thereafter	9,901
	Total	$	39,611
	Gathering, Transportation and Processing Charges. The Company has entered into contracts that provide firm gathering and transportation capacity on pipeline systems and firm processing charges. The remaining terms on these contracts range from 2 to 8 years and require the Company to pay gathering, transportation and processing charges regardless of the amount of pipeline capacity utilized by the Company. The Company paid $42.6 million, $45.0 million and $35.3 million of firm gathering and transportation charges for the years ended December 31, 2013, 2012 and 2011, respectively. The Company paid $4.6 million, $6.2 million and $5.0 million of firm processing charges for the years ended December 31, 2013, 2012 and 2011, respectively. All gathering and transportation costs, including demand charges and processing charges, are included in gathering, transportation and processing expense in the Consolidated Statements of Operations.
	The amounts in the table below represent the Company’s gross future minimum transportation demand and firm processing charges. However, the Company will record in its financial statements only the Company’s proportionate share based on the Company’s working interest and net revenue interest, which will vary from property to property.
		As of December 31, 2013
		(in thousands)
	2014	$	36,905
	2015	36,717
	2016	35,466
	2017	33,085
	2018	33,521
	Thereafter	63,813
	Total	$	239,507
	Lease and Other Commitments. The Company has one take-or-pay purchase agreement for supply of carbon dioxide (“CO2”), which has a total financial commitment of $1.7 million as of December 31, 2013. The CO2 is for use in fracture stimulation operations. Under this contract, the Company is obligated to purchase a minimum monthly volume at a set price. If the Company takes delivery of less than the minimum required amount, the Company is responsible for full payment (deficiency payment) in December 2015.
	The Company leases office space, vehicles and certain equipment under non-cancelable operating leases. Office lease expense was $1.8 million, $2.0 million and $1.5 million for the years ended December 31, 2013, 2012 and 2011, respectively. Additionally, the Company has entered into various long-term agreements for telecommunication services. Future minimum annual payments under lease and other agreements are as follows:
		As of December 31, 2013
		(in thousands)
	2014	$	4,655
	2015 (1)	10,014
	2016	2,678
	2017	2,517
	2018	2,525
	Thereafter	633
	Total (2)	$	23,022
	-1	Includes a drilling carry agreement in the amount of $8.5 million related to acreage in the Powder River Basin. As of December 31, 2013, the Company has satisfied $1.6 million of this carry. The Company will owe the remaining carry balance if not satisfied by October 1, 2015.
	-2	The total includes the lease payments for 19,200 square feet of the Denver office which is under a sublease agreement as of December 31, 2013.
	Litigation. The Company is subject to litigation, claims and governmental and regulatory proceedings arising in the course of ordinary business. It is the opinion of the Company’s management that current claims and litigation involving the Company are not likely to have a material adverse effect on its consolidated balance sheets, cash flows or statements of operations.

Guarantor_Subsidiaries

Guarantor Subsidiaries	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Guarantor Subsidiaries	'
	Guarantor Subsidiaries
	In addition to the Amended Credit Facility, the 7.625% Senior Notes, the 7.0% Senior Notes and the Convertible Notes, which are registered securities, are jointly and severally guaranteed on a full and unconditional basis by the 100% owned subsidiaries (“Guarantor Subsidiaries”) of the Company (referred to in this Note 14 as the “Parent Issuer”). Presented below are the Company’s condensed consolidating balance sheets, statements of operations, statements of other comprehensive income (loss) and statements of cash flows, as required by Rule 3-10 of Regulation S-X of the Securities Exchange Act of 1934, as amended.
	The following condensed consolidating financial statements have been prepared from the Company’s financial information on the same basis of accounting as the Consolidated Financial Statements. Investments in the subsidiaries are accounted for under the equity method. Accordingly, the entries necessary to consolidate the Company and the Guarantor Subsidiaries are reflected in the intercompany eliminations column.
	Condensed Consolidating Balance Sheets
		As of December 31, 2013
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Assets:
	Current assets	$	154,794		$	2,453		$	—		$	157,247
	Property and equipment, net	2,088,591			113,905			—			2,202,496
	Intercompany receivable (payable)	155,909			(155,909		)	—			—
	Investment in subsidiaries	(44,976		)	—			44,976			—
	Noncurrent assets	21,770			—			—			21,770
	Total assets	$	2,376,088		$	(39,551	)	$	44,976		$	2,381,513
	Liabilities and Stockholders’ Equity:
	Current liabilities	$	192,093		$	626		$	—		$	192,719
	Long-term debt	979,082			—			—			979,082
	Deferred income taxes	159,139			2,187			—			161,326
	Other noncurrent liabilities	40,056			2,612			—			42,668
	Stockholders’ equity	1,005,718			(44,976		)	44,976			1,005,718
	Total liabilities and stockholders’ equity	$	2,376,088		$	(39,551	)	$	44,976		$	2,381,513
		As of December 31, 2012
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Assets:
	Current assets	$	226,013		$	2,326		$	—		$	228,339
	Property and equipment, net	2,514,240			97,097			—			2,611,337
	Intercompany receivable (payable)	141,272			(141,272		)	—			—
	Investment in subsidiaries	(47,533		)	—			47,533			—
	Noncurrent assets	29,773			—			—			29,773
	Total assets	$	2,863,765		$	(41,849	)	$	47,533		$	2,869,449
	Liabilities and Stockholders’ Equity:
	Current liabilities	$	212,117		$	1,016		$	—		$	213,133
	Long-term debt	1,156,654			—			—			1,156,654
	Deferred income taxes	264,113			2,251			—			266,364
	Other noncurrent liabilities	48,106			2,417			—			50,523
	Stockholders’ equity	1,182,775			(47,533		)	47,533			1,182,775
	Total liabilities and stockholders’ equity	$	2,863,765		$	(41,849	)	$	47,533		$	2,869,449
	Condensed Consolidating Statements of Operations
		Year Ended December 31, 2013
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Operating and other revenues	$	536,557		$	31,536		$	—		$	568,093
	Operating expenses	(654,189		)	(28,979		)	—			(683,168		)
	General and administrative	(64,902		)	—			—			(64,902		)
	Interest income and other income (expense)	(131,389		)	—			—			(131,389		)
	Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	(313,923		)	2,557			—			(311,366		)
	Benefit from income taxes	118,633			—			—			118,633
	Equity in earnings (loss) of subsidiaries	2,557			—			(2,557		)	—
	Net income (loss)	$	(192,733	)	$	2,557		$	(2,557	)	$	(192,733	)
		Year Ended December 31, 2012
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Operating and other revenues	$	682,209		$	17,986		$	—		$	700,195
	Operating expenses	(590,185		)	(18,135		)	—			(608,320		)
	General and administrative	(68,666		)	—			—			(68,666		)
	Interest income and other income (expense)	(20,991		)	—			—			(20,991		)
	Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	2,367			(149		)	—			2,218
	Provision for income taxes	(1,636		)	—			—			(1,636		)
Equity in earnings (loss) of subsidiaries	(149		)	—			149			—
Net income (loss)	$	582		$	(149	)	$	149		$	582
	Year Ended December 31, 2011
	Parent			Guarantor			Intercompany			Consolidated
	Issuer			Subsidiaries			Eliminations
	(in thousands)
Operating and other revenues	$	770,106		$	15,518		$	—		$	785,624
Operating expenses	(541,759		)	(55,430		)	—			(597,189		)
General and administrative	(66,780		)	—			—			(66,780		)
Interest and other income (expense)	(73,276		)	—			—			(73,276		)
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	88,291			(39,912		)	—			48,379
Provision for income taxes	(17,672		)	—			—			(17,672		)
Equity in earnings (loss) of subsidiaries	(39,912		)	—			39,912			—
Net income (loss)	$	30,707		$	(39,912	)	$	39,912		$	30,707
Condensed Consolidating Statements of Comprehensive Income (Loss)
	Year Ended December 31, 2013
	Parent			Guarantor			Intercompany			Consolidated
	Issuer			Subsidiaries			Eliminations
	(in thousands)
Net Income (Loss)	$	(192,733	)	$	2,557		$	(2,557	)	$	(192,733	)
Other Comprehensive Income (Loss), net of tax:
Effect of derivative financial instruments	(4,663		)	—			—			(4,663		)
Other comprehensive loss	(4,663		)	—			—			(4,663		)
Comprehensive Income (Loss)	$	(197,396	)	$	2,557		$	(2,557	)	$	(197,396	)
	Year Ended December 31, 2012
	Parent			Guarantor			Intercompany			Consolidated
	Issuer			Subsidiaries			Eliminations
	(in thousands)
Net Income (Loss)	$	582		$	(149	)	$	149		$	582
Other Comprehensive Income (Loss), net of tax:
Effect of derivative financial instruments	(50,712		)	—			—			(50,712		)
Other comprehensive loss	(50,712		)	—			—			(50,712		)
Comprehensive Income (Loss)	$	(50,130	)	$	(149	)	$	149		$	(50,130	)
	Year Ended December 31, 2011
	Parent			Guarantor			Intercompany			Consolidated
	Issuer			Subsidiaries			Eliminations
	(in thousands)
Net Income (Loss)	$	30,707		$	(39,912	)	$	39,912		$	30,707
Other Comprehensive Income (Loss), net of tax:
Effect of derivative financial instruments	8,215			—			—			8,215
Other comprehensive loss	8,215			—			—			8,215
Comprehensive Income (Loss)	$	38,922		$	(39,912	)	$	39,912		$	38,922
Condensed Consolidating Statements of Cash Flows
	Year Ended December 31, 2013
	Parent			Guarantor			Intercompany			Consolidated
	Issuer			Subsidiaries			Eliminations
	(in thousands)
Cash flows from operating activities	$	240,233		$	25,032		$	—		$	265,265
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(407,994		)	(37,485		)	—			(445,479		)
Additions to furniture, fixtures and other	(2,254		)	—			—			(2,254		)
Proceeds from sale of properties and other investing activities	310,704			—			—			310,704
Cash flows from financing activities:
Proceeds from debt	420,000			—			—			420,000
Principal and redemption premium payments on debt	(576,422		)	—			—			(576,422		)
Intercompany transfers	(12,453		)	12,453			—			—
Other financing activities	3,336			—			—			3,336
Change in cash and cash equivalents	(24,850		)	—			—			(24,850		)
Beginning cash and cash equivalents	79,395			50			—			79,445
Ending cash and cash equivalents	$	54,545		$	50		$	—		$	54,595
	Year Ended December 31, 2012
	Parent			Guarantor			Intercompany			Consolidated
	Issuer			Subsidiaries			Eliminations
	(in thousands)
Cash flows from operating activities	$	382,164		$	6,272		$	—		$	388,436
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(929,370		)	(29,284		)	—			(958,654		)
Additions to furniture, fixtures and other	(7,231		)	—			—			(7,231		)
Proceeds from sale of properties and other investing activities	303,818			25,070			—			328,888
Cash flows from financing activities:
Proceeds from debt	875,826			—			—			875,826
Principal and redemption premium payments on debt	(595,386		)	—			—			(595,386		)
Intercompany transfers	2,058			(2,058		)	—			—
Other financing activities	(9,765		)	—			—			(9,765		)
Change in cash and cash equivalents	22,114			—			—			22,114
Beginning cash and cash equivalents	57,281			50			—			57,331
Ending cash and cash equivalents	$	79,395		$	50		$	—		$	79,445
	Year Ended December 31, 2011
	Parent			Guarantor			Intercompany			Consolidated
	Issuer			Subsidiaries			Eliminations
	(in thousands)
Cash flows from operating activities	$	486,579		$	(7,231	)	$	—		$	479,348
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(884,099		)	(63,107		)	—			(947,206		)
Additions to furniture, fixtures and other	(11,556		)	414			—			(11,142		)
Proceeds from sale of properties and other investing activities	1,702			—			—			1,702
Cash flows from financing activities:
Proceeds from debt	800,000			—			—			800,000
Principal and redemption premium payments on debt	(330,000		)	—			—			(330,000		)
Intercompany transfers	(69,973		)	69,973			—			—
Other financing activities	5,938			1			—			5,939
Change in cash and cash equivalents	(1,409		)	50			—			(1,359		)
Beginning cash and cash equivalents	58,690			—			—			58,690
Ending cash and cash equivalents	$	57,281		$	50		$	—		$	57,331

Summary_of_Significant_Account1

Summary of Significant Accounting Policies - (Policies)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation. The accompanying consolidated financial statements include the accounts of the Company. These statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). All intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	'
	Use of Estimates. In the course of preparing the Company’s financial statements in accordance with GAAP, management makes various assumptions, judgments and estimates to determine the reported amount of assets, liabilities, revenues and expenses and in the disclosure of commitments and contingencies. Changes in these assumptions, judgments and estimates will occur as a result of the passage of time and the occurrence of future events and, accordingly, actual results could differ from amounts initially established.
	Areas requiring the use of assumptions, judgments and estimates relate to the expected cash settlement of the Company’s 5% Convertible Senior Notes due 2028 (“Convertible Notes”) in computing diluted earnings per share, volumes of oil, natural gas and NGL reserves used in calculating depreciation, depletion and amortization (“DD&A”), the amount of expected future cash flows used in determining possible impairments of oil and gas properties and the amount of future capital costs used in these calculations. Assumptions, judgments and estimates also are required in determining asset retirement obligations, the timing of dry hole costs, impairments of proved and unproved properties, valuing deferred tax assets and estimating fair values of derivative instruments and stock-based payment awards.
Oil and Gas Properties	'
	Oil and Gas Properties. The Company’s oil, gas and NGL exploration and production activities are accounted for using the successful efforts method. Under this method, all property acquisition costs and costs of exploratory and development wells are capitalized when incurred, pending determination of whether the well has found proved reserves. If an exploratory well does not find proved reserves, the costs of drilling the well are charged to expense and included within cash flows from investing activities in the Consolidated Statements of Cash Flows. If an exploratory well does find proved reserves, the costs remain capitalized and are included within additions to oil and gas properties within cash flows from investing activities in the Consolidated Statements of Cash Flows when incurred. The costs of development wells are capitalized whether proved reserves are added or not. Oil and gas lease acquisition costs are also capitalized.
	Other exploration costs, including certain geological and geophysical expenses and delay rentals for oil and gas leases, are charged to expense as incurred. The sale of a partial interest in a proved property is accounted for as a cost recovery and no gain or loss is recognized as long as this treatment does not significantly affect the unit-of-production amortization rate. A gain or loss is recognized for all other sales of proved properties and is classified in other operating revenues. Maintenance and repairs are charged to expense, and renewals and betterments are capitalized to the appropriate property and equipment accounts.
	Unproved oil and gas property costs are transferred to proved oil and gas properties if the properties are subsequently determined to be productive or are assigned proved reserves. Proceeds from sales of partial interests in unproved leases are accounted for as a recovery of cost without recognizing any gain until all costs are recovered. Unproved oil and gas properties are assessed periodically for impairment based on remaining lease terms, drilling results, reservoir performance, commodity price outlooks, future plans to develop acreage and other relevant matters.
	Materials and supplies consist primarily of tubular goods and well equipment to be used in future drilling operations or repair operations and are carried at the lower of cost or market value, on a first-in, first-out basis.
	The following table sets forth the net capitalized costs and associated accumulated DD&A and non-cash impairments relating to the Company’s oil, natural gas and NGL producing activities:
		As of December 31,
		2013				2012
		(in thousands)
	Proved properties	$	485,427			$	387,242
	Wells and related equipment and facilities	2,192,754				2,625,891
	Support equipment and facilities	177,224				304,914
	Materials and supplies	8,518				13,220
	Total proved oil and gas properties	$	2,863,923			$	3,331,267
	Unproved properties	239,925				384,486
	Wells and facilities in progress	56,674				72,721
	Total unproved oil and gas properties, excluded from amortization	$	296,599			$	457,207
	Accumulated depreciation, depletion, amortization and impairment	(976,339		)		(1,203,495		)
	Total oil and gas properties, net	$	2,184,183			$	2,584,979
	Net changes in capitalized exploratory well costs for the years ended December 31, 2013, 2012 and 2011, respectively, are reflected in the following table:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Beginning of period	$	—			$	—			$	9,041
	Additions to capitalized exploratory well costs pending the determination of proved reserves	—				—				110
	Reclassifications to wells, facilities and equipment based on the determination of proved reserves	—				—				(6,179		)
	Exploratory well costs charged to dry hole costs and abandonment expense	—				—				(2,972		)
	End of period	$	—			$	—			$	—
	All exploratory wells are evaluated for economic viability within one year of well completion. Exploratory wells that discover potentially economic reserves in areas where a major capital expenditure would be required before production could begin, and where the economic viability of that major capital expenditure depends upon the successful completion of further exploratory work in the area, remain capitalized if the well finds a sufficient quantity of reserves to justify its completion as a producing well and the Company is making sufficient progress assessing the reserves and the economic and operating viability of the project.
	The Company reviews proved oil and gas properties on a field-by-field basis for impairment on an annual basis or whenever events and circumstances indicate that a decline in the recoverability of their carrying value may have occurred. The Company estimates the expected undiscounted future cash flows of its oil and gas properties and compares such undiscounted future cash flows to the carrying amount of the oil and gas properties to determine if the carrying amount is recoverable. If the carrying value of a property exceeds the undiscounted future cash flows, the Company will impair the carrying value to fair value based on an analysis of quantitative and qualitative factors. The factors used to determine fair value include, but are not limited to, recent sales prices of comparable properties, the present value of future cash flows, net of estimated operating and development costs using estimates of reserves, future commodity pricing, future production estimates, anticipated capital expenditures and various discount rates commensurate with the risk and current market conditions associated with realizing the expected cash flows projected.
	The Company recognized non-cash impairment charges, which were included within impairment, dry hole costs and abandonment expense in the Consolidated Statements of Operations, as follows:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Non-cash impairment of proved oil and gas properties	$	206,953		(1)	$	—			$	82,814		(2)
	Non-cash impairment of unproved oil and gas properties	19,598			(3)	37,348			(4)	17,464			(5)
	Dry hole costs	1,124				21,012				13,391
	Abandonment expense	10,723				9,509				3,930
	Total non-cash impairment, dry hole costs and abandonment expense	$	238,398			$	67,869			$	117,599
	-1	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2013 related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
	-2	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2011 related to properties within the Powder River and Wind River Basins. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.
	-3	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2013 was comprised of $17.1 million related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value and $2.5 million related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
	-4	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2012 related to certain unproved oil and gas properties within exploration projects primarily as a result of unfavorable natural gas exploratory results, unfavorable market conditions or no future plans to evaluate the remaining acreage.
	-5	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2011 related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value.
	The provision for DD&A of oil and gas properties is calculated on a field-by-field basis using the unit-of-production method. Natural gas is converted to barrel of oil equivalents, Boe, at the standard rate of six Mcf to one barrel. Estimated future dismantlement, restoration and abandonment costs, which are net of estimated salvage values, are taken into consideration by this calculation.
Environmental Liabilities	'
	Environmental Liabilities. Environmental expenditures that relate to an existing condition caused by past operations and that do not contribute to current or future revenue generation are expensed. Environmental liabilities are accrued when environmental assessments and/or clean-ups are probable, and the costs can be reasonably estimated.
Revenue Recognition	'
	Revenue Recognition. The Company records revenues from the sales of oil, natural gas and NGLs when delivery to the purchaser has occurred. The Company uses the sales method to account for gas and NGL imbalances. Under this method, revenue is recorded on the basis of gas and NGLs actually sold by the Company. In addition, the Company records revenues for its share of gas and NGLs sold by other owners that cannot be volumetrically balanced in the future due to insufficient remaining reserves. The Company also reduces revenues for other owners’ gas and NGLs sold by the Company that cannot be volumetrically balanced in the future due to insufficient remaining reserves. The Company’s remaining over- and under- produced gas and NGLs balancing positions are considered in the Company’s proved oil, gas and NGL reserves. Imbalances at December 31, 2013 and 2012 were not material.
Derivative Instruments and Hedging Activities	'
	Derivative Instruments and Hedging Activities. The Company periodically uses derivative financial instruments to achieve a more predictable cash flow from its oil, natural gas and NGL sales by reducing its exposure to price fluctuations. Derivative instruments are recorded at fair market value and are included in the Consolidated Balance Sheets as assets or liabilities.
Income Taxes	'
	Income Taxes. Income taxes are provided for the tax effects of transactions reported in the financial statements and consist of taxes currently payable plus deferred income taxes related to certain income and expenses recognized in different periods for financial and income tax reporting purposes. Deferred income tax assets and liabilities represent the future tax return consequences of those differences, which will either be taxable or deductible when assets are recovered or liabilities are settled. Deferred income taxes also include tax credits and net operating losses that are available to offset future income taxes. Deferred income taxes are measured by applying currently enacted tax rates.
	The Company accounts for uncertainty in income taxes for tax positions taken or expected to be taken in a tax return. Only tax positions that meet the more-likely-than-not recognition threshold are recognized.
Earnings/Loss Per Share	'
	Earnings/Loss Per Share. Basic net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding during each period. Diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding and other dilutive securities. Potentially dilutive securities for the diluted net income per common share calculations consist of nonvested equity shares of common stock, in-the-money outstanding stock options to purchase the Company’s common stock and shares into which the Convertible Notes are convertible. No potential common shares are included in the computation of any diluted per share amount when a net loss exists, as was the case for the year ended December 31, 2013.
	In satisfaction of its obligation upon conversion of the Convertible Notes, the Company may elect to deliver, at its option, cash, shares of its common stock or a combination of cash and shares of its common stock. As of December 31, 2013, the Company expected to settle the remaining Convertible Notes in cash. Therefore, the treasury stock method was used to measure the potentially dilutive impact of shares associated with that remaining conversion feature. The Company has the right at any time with at least 30 days’ notice to call the Convertible Notes and the holders have the right to require the Company to purchase the notes on March 20, 2015, March 20, 2018 and March 20, 2023. The Convertible Notes have not been dilutive since their issuance in March 2008 and, therefore, did not impact the diluted net income (loss) per common share calculation for the years ended December 31, 2012 and 2011. The diluted net income (loss) per common share excludes the anti-dilutive effect of 3,162,436 and 115,215 shares of stock options and nonvested equity shares of common stock for the years ended December 31, 2012 and 2011, respectively.
Industry Segment and Geographic Information	'
	Industry Segment and Geographic Information. The Company operates in one industry segment, which is the development and production of crude oil, natural gas and NGLs, and all of the Company’s operations are conducted in the continental United States. Consequently, the Company currently reports as a single industry segment.
New Accounting Pronouncements	'
	New Accounting Pronouncements. In January 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2013-1, Balance Sheet: Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities, which amended FASB Accounting Standards Codification (“ASC”) Topic 210, Balance Sheet. The main objective in developing this update was to address implementation issues about the scope of ASU 2011-11, Balance Sheet: Disclosures about Offsetting Assets and Liabilities. The amendments clarify that the scope of ASU 2011-11 applies to derivatives accounted for in accordance with Topic 815, Derivatives and Hedging, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with ASC 210-20-45 or ASC 815-10-45 or subject to an enforceable master netting arrangement or similar agreement. This provision is effective for fiscal years beginning on or after January 1, 2013. Adoption of this update did not have a material impact on the Company’s disclosures or financial statements.
	In February 2013, the FASB issued ASU 2013-2, Comprehensive Income: Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, which amended ASC Topic 220, Comprehensive Income. The objective of this update was to improve the reporting of reclassifications out of accumulated other comprehensive income. The amendment did not change the requirements for reporting net income or other comprehensive income in financial statements. However, the amendment required an entity to provide information about the amounts reclassified out of accumulated other comprehensive income by component. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income but only if the amount reclassified is required under U.S. GAAP to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures required under U.S. GAAP that provide additional detail about those amounts. This provision is effective for interim and annual periods beginning after December 15, 2012. Adoption of this update did not have a material impact on the Company’s disclosures or financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - (Tables)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Summary of Accounts Receivable	'
	Accounts Receivable. Accounts receivable is comprised of the following:
		As of December 31,
		2013				2012
		(in thousands)
	Accrued oil, gas and NGL sales	$	67,583			$	69,482
	Due from joint interest owners	23,507				36,300
	Other	6,517				6,554
	Allowance for doubtful accounts	(21		)		(325		)
	Total accounts receivable	$	97,586			$	112,011
Net Capitalized Costs and Associated Accumulated DD&A and Non Cash Impairments	'
	The following table sets forth the net capitalized costs and associated accumulated DD&A and non-cash impairments relating to the Company’s oil, natural gas and NGL producing activities:
		As of December 31,
		2013				2012
		(in thousands)
	Proved properties	$	485,427			$	387,242
	Wells and related equipment and facilities	2,192,754				2,625,891
	Support equipment and facilities	177,224				304,914
	Materials and supplies	8,518				13,220
	Total proved oil and gas properties	$	2,863,923			$	3,331,267
	Unproved properties	239,925				384,486
	Wells and facilities in progress	56,674				72,721
	Total unproved oil and gas properties, excluded from amortization	$	296,599			$	457,207
	Accumulated depreciation, depletion, amortization and impairment	(976,339		)		(1,203,495		)
	Total oil and gas properties, net	$	2,184,183			$	2,584,979
Net Change in Capitalized Exploratory Well Costs	'
	Net changes in capitalized exploratory well costs for the years ended December 31, 2013, 2012 and 2011, respectively, are reflected in the following table:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Beginning of period	$	—			$	—			$	9,041
	Additions to capitalized exploratory well costs pending the determination of proved reserves	—				—				110
	Reclassifications to wells, facilities and equipment based on the determination of proved reserves	—				—				(6,179		)
	Exploratory well costs charged to dry hole costs and abandonment expense	—				—				(2,972		)
	End of period	$	—			$	—			$	—
Non-Cash Impairment Charges, Included within Impairment, Dry Hole Costs and Abandonment Expense in Consolidated Statements of Operations	'
	The Company recognized non-cash impairment charges, which were included within impairment, dry hole costs and abandonment expense in the Consolidated Statements of Operations, as follows:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Non-cash impairment of proved oil and gas properties	$	206,953		(1)	$	—			$	82,814		(2)
	Non-cash impairment of unproved oil and gas properties	19,598			(3)	37,348			(4)	17,464			(5)
	Dry hole costs	1,124				21,012				13,391
	Abandonment expense	10,723				9,509				3,930
	Total non-cash impairment, dry hole costs and abandonment expense	$	238,398			$	67,869			$	117,599
	-1	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2013 related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
	-2	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2011 related to properties within the Powder River and Wind River Basins. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.
	-3	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2013 was comprised of $17.1 million related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value and $2.5 million related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
	-4	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2012 related to certain unproved oil and gas properties within exploration projects primarily as a result of unfavorable natural gas exploratory results, unfavorable market conditions or no future plans to evaluate the remaining acreage.
	-5	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2011 related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value.
Accounts Payable and Accrued Liabilities	'
	Accounts Payable and Accrued Liabilities. Accounts payable and accrued liabilities are comprised of the following:
		As of December 31,
		2013				2012
		(in thousands)
	Accrued drilling, completion and facility costs	$	54,750			$	42,094
	Accrued lease operating, gathering, transportation and processing expenses	17,317				16,862
	Accrued general and administrative expenses	14,605				13,054
	Trade payables and other	29,256				53,007
	Total accounts payable and accrued liabilities	$	115,928			$	125,017
Calculation of Basic and Diluted Earnings Per Share	'
	The following table sets forth the calculation of basic and diluted net income (loss) per share:
		Year Ended December 31,
		2013				2012				2011
		(in thousands, except per share amounts)
	Net income (loss)	$	(192,733	)		$	582			$	30,707
	Basic weighted-average common shares outstanding in period	47,497				47,195				46,536
	Add dilutive effects of stock options and nonvested equity shares of common stock	—				159				701
	Diluted weighted-average common shares outstanding in period	47,497				47,354				47,237
	Basic net income (loss) per common share	$	(4.06	)		$	0.01			$	0.66
	Diluted net income (loss) per common share	$	(4.06	)		$	0.01			$	0.65

Supplemental_Disclosures_of_Ca1

Supplemental Disclosures of Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information	'
	Supplemental cash flow information is as follows:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Cash paid for interest, net of amount capitalized	$	94,205		$	83,718		$	36,504
	Cash paid for income taxes	1,163			10			(8,128		)
	Supplemental disclosures of non-cash investing and financing activities:
	Current liabilities	75,340			49,598			66,257
	Net increase (decrease) in asset retirement obligations	(6,996		)	(25,236		)	13,185
	Treasury stock acquired for employee stock option exercises	—			—			592
	Retirement of treasury stock	1,778			2,513			4,436

Divestitures_Tables

Divestitures - (Tables)	12 Months Ended
	Dec. 31, 2013
Assets Held for Sale [Abstract]	'
Schedule of Carrying Amounts by Major Asset Class within the Disposal Group	'
	The carrying amounts by major asset class within the disposal group are summarized below:
		As of December 10, 2013
		(in thousands)
	Assets
	Proved properties	$	1,058,319
	Unproved properties	10,598
	Furniture, equipment and other	4,380
	Accumulated depreciation, depletion, amortization and impairment	(706,810		)
	Other Assets	1,533
	Total assets	$	368,020
	Liabilities
	Asset retirement obligation	$	13,471
	Lease financing obligation	45,190
	Total liabilities	$	58,661
	Net assets	$	309,359

LongTerm_Debt_Tables

Long-Term Debt - (Tables)	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Outstanding Debt	'
	The Company’s outstanding debt is summarized below:
			As of December 31, 2013								As of December 31, 2012
		Maturity Date	Principal			Unamortized			Carrying		Principal		Unamortized			Carrying
						Discount			Amount				Discount			Amount
			(in thousands)
	Amended Credit Facility (1)	October 31, 2016	$	115,000		$	—		$	115,000	$	—	$	—		$	—
	9.875% Senior Notes (2)	July 15, 2016	—			—			—		250,000		(7,209		)	242,791
	Convertible Notes (3)	March 15, 2028 (4)	25,344			—			25,344		25,344		—			25,344
	7.625% Senior Notes (5)	October 1, 2019	400,000			—			400,000		400,000		—			400,000
	7.0% Senior Notes (6)	October 15, 2022	400,000			—			400,000		400,000		—			400,000
	Lease Financing Obligation (7)	August 10, 2020	43,329			—			43,329		97,596		—			97,596
	Total Debt		$	983,673		$	—		$	983,673	$	1,172,940	$	(7,209	)	$	1,165,731
	Less: Current Portion of Long-Term Debt		4,591			—			4,591		9,077		—			9,077
	Total Long-Term Debt		$	979,082		$	—		$	979,082	$	1,163,863	$	(7,209	)	$	1,156,654
	-1	The recorded value of the Amended Credit Facility approximates its fair value due to its floating rate structure and on financing terms currently available to the Company.
	-2	The aggregate estimated fair value of the 9.875% Senior Notes was $271.9 million as of December 31, 2012 based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013.
	-3	The aggregate estimated fair value of the Convertible Notes was approximately $25.1 million and $25.3 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.
	-4	The Company has the right at any time, with at least 30 days’ notice, to call the Convertible Notes, and the holders have the right to require the Company to purchase the notes on each of March 20, 2015, March 20, 2018 and March 20, 2023.
	-5	The aggregate estimated fair value of the 7.625% Senior Notes was approximately $430.2 million and $435.0 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.
	-6	The aggregate estimated fair value of the 7.0% Senior Notes was approximately $417.0 million and $413.8 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.
	-7	The aggregate estimated fair value of the Lease Financing Obligation was approximately $41.7 million and $97.7 million as of December 31, 2013 and 2012, respectively. Because there is no active, public market for the Lease Financing Obligation, the aggregate estimated fair value was based on market-based parameters of comparable term secured financing instruments.
Cash and Non-Cash Portion of Interest Expense Related to Long Term Debt	'
	The following table summarizes, for the periods indicated, the cash or accrued portion of interest expense related to the Amended Credit Facility, 9.875% Senior Notes, Convertible Notes, 7.625% Senior Notes, 7.0% Senior Notes and the Lease Financing Obligation along with the non-cash portion resulting from the amortization of the debt discount and transaction costs through interest expense:
		As of December 31,
		2013			2012			2011
		(in thousands)
	Amended Credit Facility (1)
	Cash interest	$	6,802		$	5,652		$	5,432
	Non-cash interest	2,342			2,342			2,922
	9.875% Senior Notes (2)
	Cash interest	$	13,373		$	24,688		$	24,688
	Non-cash interest	1,361			2,571			2,485
	Convertible Notes (3)
	Cash interest	$	1,267		$	2,909		$	8,625
	Non-cash interest	6			1,771			7,548
	7.625% Senior Notes (4)
	Cash interest	$	30,500		$	30,500		$	7,964
	Non-cash interest	1,070			1,066			332
	7.0% Senior Notes (5)
	Cash interest	$	28,000		$	22,400		$	—
	Non-cash interest	795			659			—
	Lease Financing Obligation (6)
	Cash interest	$	2,852		$	1,353		$	—
	Non-cash interest	30			15			—
	-1	Cash interest includes amounts related to interest and commitment fees paid on the Amended Credit Facility and participation and fronting fees paid on the letter of credit.
	-2	The stated interest rate for the 9.875% Senior Notes was 9.875% per annum with an effective interest rate of 11.2% per annum. The Company redeemed the 9.875% Senior Notes in full on July 15, 2013.
	-3	The stated interest rate for the Convertible Notes is 5% per annum. The effective interest rate of the Convertible Notes includes amortization of the debt discount, which represented the fair value of the equity conversion feature at the time of issue. The stated interest rate of 5% on the Convertible Notes will is the effective interest rate of the $25.3 million remaining principal balance, as the related debt discount was fully amortized as of March 31, 2012.
	-4	The stated interest rate for the 7.625% Senior Notes is 7.625% per annum with an effective interest rate of 8.0% per annum.
	-5	The stated interest rate for the 7.0% Senior Notes is 7.0% per annum with an effective interest rate of 7.2% per annum.
	-6	The effective interest rate for the Lease Financing Obligation is 3.3% per annum.

Asset_Retirement_Obligations_T

Asset Retirement Obligations - (Tables)	12 Months Ended
	Dec. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Schedule of Asset Retirement Obligations	'
	A reconciliation of the Company’s asset retirement obligations for the year ended December 31, 2013, 2012 and 2011 is as follows:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Beginning of period	$	47,616		$	69,302		$	53,079
	Liabilities incurred	2,359			4,046			13,186
	Liabilities settled	(1,096		)	(871		)	(1,046		)
	Disposition of properties	(13,543		)	(33,560		)	—
	Accretion expense	3,481			4,421			4,083
	Revisions to estimate	4,188			4,278			—
	End of period	$	43,005		$	47,616		$	69,302
	Less: Current asset retirement obligations	3,805			1,566			715
	Long-term asset retirement obligations	$	39,200		$	46,050		$	68,587

Fair_Value_Measurements_Tables

Fair Value Measurements - (Tables)	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Schedule of Fair Value of Proved and Unproved Properties at Net Carrying Value [Table Text Block]	'
				Fair Value Measurements Using
		Net Carrying Value as of December 31, 2013		Level 1		Level 2		Level 3
		(in thousands)
	Proved property impairments (1)	$	1,937,913	$	—	$	—	$	206,953
	Unproved property impairments (1)	246,270		—		—		19,598
	(1) See Note 2 for additional details on impairment expense recognized.
				Fair Value Measurements Using
		Net Carrying Value as of December 31, 2012		Level 1		Level 2		Level 3
		(in thousands)
	Proved property impairments (1)	$	2,179,171	$	—	$	—	$	—
	Unproved property impairments (1)	405,808		—		—		37,348
	(1) See Note 2 for additional details on impairment expense recognized.
Fair Value, Balance Sheet Grouping	'
	The following tables set forth by level within the fair value hierarchy the Company’s financial assets and financial liabilities that were measured at fair value on a recurring basis. Assets and liabilities are classified in their entirety 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 assets and liabilities and their placement within the fair value hierarchy levels.
		As of December 31, 2013
		Level 1		Level 2		Level 3		Total
		(in thousands)
	Assets
	Deferred Compensation Plan	$	941	$	—	$	—	$	941
	Cash Equivalents - Money Market Funds	53		—		—		53
	Commodity Derivatives	—		11,483		—		11,483
	Liabilities
	Commodity Derivatives	$	—	$	14,771	$	—	$	14,771
		As of December 31, 2012
		Level 1		Level 2		Level 3		Total
		(in thousands)
	Assets
	Deferred Compensation Plan	$	966	$	—	$	—	$	966
	Cash Equivalents - Money Market Funds	53		—		—		53
	Commodity Derivatives	—		40,432		—		40,432
	Liabilities
	Commodity Derivatives	$	—	$	7,875	$	—	$	7,875

Derivative_Instruments_Tables

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Fair Value Amounts of Derivative Instruments	'
	The following table summarizes the location, as well as the gross and net fair value amounts of all derivative instruments presented on the Consolidated Balance Sheets as of the dates indicated.
		As of December 31, 2013
	Balance Sheet	Gross Amounts of				Gross Amounts				Net Amounts of Assets
		Recognized Assets				Offset in the Balance				Presented in the Balance
						Sheet				Sheet
						(in thousands)
	Derivative assets	$	8,259			$	(8,086	)	(1)	$	173
	Deferred financing costs and other noncurrent assets	3,224				(685		)	(1)	2,539			(2)
	Total derivative assets	$	11,483			$	(8,771	)		$	2,712
		Gross Amounts of				Gross Amounts				Net Amounts of Liabilities
		Recognized				Offset in the Balance				Presented in the Balance
		Liabilities				Sheet				Sheet
						(in thousands)
	Derivative liabilities	$	(14,074	)		$	8,086		(3)	$	(5,988	)
	Derivatives and other noncurrent liabilities	(697		)		685			(3)	(12		)	(4)
	Total derivative liabilities	$	(14,771	)		$	8,771			$	(6,000	)
		As of December 31, 2012
	Balance Sheet	Gross Amounts of				Gross Amounts				Net Amounts of Assets
		Recognized Assets				Offset in the Balance				Presented in the Balance
						Sheet				Sheet
						(in thousands)
	Derivative assets	$	34,828			$	(4,848	)	(1)	$	29,980
	Deferred financing costs and other noncurrent assets	5,604				(2,623		)	(1)	2,981			(2)
	Total derivative assets	$	40,432			$	(7,471	)		$	32,961
		Gross Amounts of				Gross Amounts				Net Amounts of Liabilities
		Recognized				Offset in the Balance				Presented in the Balance
		Liabilities				Sheet				Sheet
						(in thousands)
	Derivative liabilities	$	(4,848	)		$	4,848		(3)	$	—
	Derivatives and other noncurrent liabilities	(3,027		)		2,623			(3)	(404		)	(4)
	Total derivative liabilities	$	(7,875	)		$	7,471			$	(404	)
	-1	Amounts are netted against derivative asset balances with the same counterparty, and therefore, are presented as a net asset on the Consolidated Balance Sheets.
	-2	As of December 31, 2013 and 2012, this line item on the Consolidated Balance Sheets included $19.2 million and $26.8 million of deferred financing costs and other noncurrent assets, respectively.
	-3	Amounts are netted against derivative liability balances with the same counterparty, and therefore are presented as a net liability on the Consolidated Balance Sheets.
	-4	As of December 31, 2013 and 2012, this line item on the Consolidated Balance Sheets includes $3.5 million and $4.1 million of other noncurrent liabilities, respectively.
Cash Flow Hedge Gains and Losses	'
	The following table summarizes the cash flow hedge gains, net of tax, and their locations on the Consolidated Balance Sheets and Consolidated Statements of Operations for the periods indicated:
		Derivatives Qualifying as		Year Ended December 31,
		Cash Flow Hedges		2013				2012				2011
				(in thousands)
	Amount of Gain (Loss) Recognized in AOCI (1)	Commodity Hedges		$	—			$	—			$	70,636
	Amount of Gain (Loss) Reclassified from AOCI into Income (net of tax) (1)(2)	Commodity Hedges		$	4,663			$	50,712			$	62,421
	Amount of Gain (Loss) Recognized in Income on Ineffective Hedges	Commodity Hedges		$	—			$	—			$	1,026
	-1	Presented net of income tax expense of $2.8 million and $30.5 million and income tax benefit of $4.9 million for the years ended December 31, 2013, 2012 and 2011, respectively.
	-2	Gains reclassified from AOCI into income are included in the oil, gas and NGL production revenues in the Consolidated Statements of Operations.
Financial Instruments for Hedging Volumes	'
	As of December 31, 2013, the Company had financial instruments in place to hedge the following volumes for the periods indicated:
		Year Ending December 31,
		2014			2015			2016
	Oil (Bbls)	3,211,400			1,348,700			91,000
	Natural Gas (MMbtu)	24,335,000			3,650,000			—
	Natural Gas Liquids (Bbls)	235,714			—			—
Realized and Unrealized Gains and Losses on Commodity Derivative Instruments	'
	The table below summarizes the commodity derivative gains and losses the Company recognized related to its oil, gas and NGL derivative instruments for the periods indicated:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Commodity derivative settlements on derivatives designated as cash flow hedges (1)	$	7,463			$	81,166			$	99,922
	Total commodity derivative gain (loss) (2)	(23,068		)		72,759				(14,263		)
	-1	Included in oil, gas and NGL production revenues in the Consolidated Statements of Operations.
	-2	Included in commodity derivative gain (loss) in the Consolidated Statements of Operations.

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Expense for Income Taxes	'
	The expense for income taxes consisted of the following for the periods indicated:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Current:
	Federal	$	(1,233	)	$	966		$	(18	)
	State	(352		)	886			—
	Foreign	2			1			2
	Deferred:
	Federal	(107,300		)	100			16,804
	State	(9,750		)	(317		)	884
	Total	$	(118,633	)	$	1,636		$	17,672
Reconciliation of Actual Income Tax Expense	'
	Income tax expense differed from the amounts computed by applying the U.S. federal income tax rate of 35% to pretax income from continuing operations as a result of the following:
		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Income tax expense at the federal statutory rate	$	(108,978	)	$	777		$	16,932
	State income taxes, net of federal tax effect	(6,702		)	(269		)	1,223
	Incentive stock compensation	678			635			(545		)
	Nondeductible political contributions and lobbying costs	96			271			238
	Nondeductible officer compensation	138			—			—
	Other permanent items	52			26			84
	Deferred tax related to the changes in overall state tax rates	(3,851		)	310			(286		)
	Other, net	(66		)	(114		)	26
	Income tax expense	$	(118,633	)	$	1,636		$	17,672
Components of Deferred Tax Assets and Deferred Tax Liabilities	'
	The tax effects of temporary differences that give rise to significant components of the deferred tax assets and deferred tax liabilities at December 31, 2013 and 2012 are presented below:
		As of December 31,
		2013			2012
		(in thousands)
	Current:
	Deferred tax assets (liabilities):
	Derivative instruments	$	(89	)	$	(13,108	)
	Accrued expenses	400			409
	Bad debt expense	8			122
	Prepaid expenses	(648		)	(776		)
	Other	130			(399		)
	Total current deferred tax assets (liabilities)	$	(199	)	$	(13,752	)
	Long-term:
	Deferred tax assets:
	Net operating loss carryforward	$	75,511		$	39,634
	Deferred offering costs	1,243			1,333
	Stock-based compensation	14,200			8,117
	Deferred rent	962			1,276
	Long-term derivative instruments	1,306			878
	Minimum tax credit carryforward	688			1,315
	Deferred compensation	999			379
	State tax credit carryfowards	5,871			4,646
	Production payment loan	3,839			8,374
	Financing obligation	16,227			36,776
	Other	222			—
	Less: Valuation allowance	(5,871		)	(4,646		)
	Total long-term deferred tax assets	115,197			98,082
	Deferred tax liabilities:
	Oil and gas properties	(276,523		)	(364,446		)
	Total long-term deferred tax liabilities	(276,523		)	(364,446		)
	Net long-term deferred tax liabilities	$	(161,326	)	$	(266,364	)

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Schedule of Stockholders Equity	'
	The following table reflects the activity in the Company’s common and treasury stock for the periods indicated:
		Year Ended December 31,
		2013			2012			2011
	Common Stock Outstanding:
	Shares at beginning of period	48,150,475			47,809,903			46,813,269
	Exercise of common stock options	259,699			36,560			836,833
	Shares issued for 401(k) plan	47,235			41,415			20,913
	Shares issued for directors' fees	52,081			12,973			7,636
	Shares issued for nonvested equity shares of common stock	1,081,259			454,666			353,716
	Shares retired or forfeited	(438,301	)		(205,042	)		(222,464	)
	Shares at end of period	49,152,448			48,150,475			47,809,903
	Treasury Stock:
	Shares at beginning of period	—			—			—
	Treasury stock acquired	96,880			92,393			113,715
	Treasury stock retired	(96,880	)		(92,393	)		(113,715	)
	Shares at end of period	—			—			—
Schedule of Accumulated Other Comprehensive Income	'
	The components of accumulated other comprehensive income and related tax effects for the years ended December 31, 2011, 2012 and 2013 were as follows:
		Gross				Tax Effect				Net of Tax
		(in thousands)
	Accumulated other comprehensive income — December 31, 2010	$	76,613			$	(28,784	)		$	47,829
	Unrealized change in fair value of hedges	113,023				(42,387		)		70,636
	Reclassification adjustment for realized gains on hedges included in net income	(99,922		)		37,501				(62,421		)
	Accumulated other comprehensive income — December 31, 2011	$	89,714			$	(33,670	)		$	56,044
	Reclassification adjustment for realized gains on hedges included in net income	(81,170		)		30,458				(50,712		)
	Accumulated other comprehensive income — December 31, 2012	$	8,544			$	(3,212	)		$	5,332
	Reclassification adjustment for realized gains on hedges included in net income	(7,465		)		2,802				(4,663		)
	Accumulated other comprehensive income — December 31, 2013	$	1,079			$	(410	)		$	669

Equity_Incentive_Compensation_1

Equity Incentive Compensation Plans and Other Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Non-Cash Stock-Based Compensation Cost Related to Equity Awards	'
	The following table presents the non-cash stock-based compensation related to equity awards for the periods indicated:
		Year Ended December 31,
		2013				2012				2011
		(in thousands)
	Common stock options	$	4,696			$	7,189			$	7,569
	Nonvested equity common stock	7,492				7,394				8,703
	Nonvested equity common stock units (1)	1,272				708				—
	Nonvested performance-based equity	2,174				1,079				3,124
	Total	$	15,634			$	16,370			$	19,396
	-1	Includes non-cash stock-based compensation related to director fees of $0.4 million and $0.2 million for the year ended December 31, 2013 and 2012, respectively.
Fair Value Assumptions and Methodology	'
	The Company estimated a 4% to 10% annual compounded forfeiture rate for the years 2012 and 2011 based on historical employee turnover and actual forfeitures.
			2012			2011
	Weighted average volatility		51	%		55	%
	Expected dividend yield		—	%		—	%
	Weighted average expected term (in years)		4.3			4.5
	Weighted average risk-free rate		1.8	%		1.9	%
Summary of Share-Based Option Activity	'
	A summary of share-based option activity under all the Company's plans as of December 31, 2013, and changes during the year then ended, is presented below:
		Shares			Weighted Average				Weighted Average		Aggregate
					Exercise Price				Remaining		Intrinsic Value
									Contractual Term
									(in years)
	Outstanding at January 1, 2013	3,020,485			$	32.4
	Granted	—			—
	Exercised	(259,699	)		24.51
	Forfeited or expired	(1,012,090	)		33.98
	Outstanding at December 31, 2013	1,748,696			32.66				1.47		$	1,239,464
	Vested and exercisable at December 31, 2013	1,310,201			$	33.37			1.96		$	1,041,448
	Expected to vest, at December 31, 2013 through the life of the options	1,718,579			28.84				2.59		5,679,748
Summary of Nonvested Equity Shares of Common Stock	'
	A summary of the Company’s nonvested equity shares of common stock as of December 31, 2013, 2012 and 2011, and changes during the years then ended, is presented below:
		Year Ended December 31,
		2013							2012					2011
		Shares			Weighted				Shares			Weighted		Shares		Weighted
					Average							Average				Average
					Grant Date							Grant Date				Grant Date
					Fair							Fair				Fair
					Value							Value				Value
	Outstanding at January 1, 2013	579,188			$	31.02			639,628			$	35.12	603,521		$	30.94
	Granted	630,715			17.98				274,679			25.62		346,956		39.49
	Vested	(270,482	)		29.82				(241,736	)		34.61		(220,006	)	31.83
	Forfeited or expired	(183,303	)		24.87				(93,383	)		33.39		(90,843	)	32.03
	Outstanding at December 31, 2013	756,118			$	22.17			579,188			$	31.02	639,628		$	35.12
	Expected to vest, at December 31, through the life of the awards	661,224			$	22.34			503,412			$	31.08	578,131		$	34.94
Summary of Nonvested Performance-Based Equity Shares of Common Stock	'
	A summary of the Company's non-vested performance-based equity shares of common stock as of December 31, 2013, 2012 and 2011, and changes during the years then ended, is presented below:
		Year Ended December 31,
		2013							2012					2011
		Shares			Weighted				Shares			Weighted		Shares		Weighted
					Average							Average				Average
					Grant Date							Grant Date				Grant Date
					Fair							Fair				Fair
					Value							Value				Value
	Outstanding at January 1, 2013	291,606			$	26.85			195,630			$	33.36	287,932		$	31.76
	Vested	—			—				(64,745	)		39.9		(81,156	)	32.1
	Modified, performance goals revised (1)	(108,933	)		27.75				(121,191	)		39.9		(192,821	)	32.18
	Modified, performance goals revised (1)	108,933			18.18				121,191			27.75		192,821		39.88
	Granted	450,544			19.99				179,987			27.57		6,760		40.52
	Forfeited or expired	(158,118	)		22.52				(19,266	)		33.82		(17,906	)	30.94
	Outstanding at December 31, 2013	584,032			$	19.8			291,606			$	26.85	195,630		$	33.36
	Expected to vest, at December 31, through the life of the awards	522,312			$	22.14			87,522			$	25.33	183,178		$	33.37
	-1	As the Compensation Committee approved new performance metrics for the vesting of performance shares in the upcoming year, a new grant date was then created for any unvested awards that were granted in previous years, and a new fair value was established for financial reporting purposes.
Directors Fees	'
	A summary of the Company’s directors’ fees and equity-based compensation for the years ended December 31, 2013, 2012 and 2011 is presented below:
		Year Ended December 31,
		2013				2012				2011
	Director fees (shares)	16,151				12,973				7,636
	Stock-based compensation (in thousands)	$	351			$	276			$	307
Deferred Compensation Liability	'
	The table below summarizes the activity in the plan during the years ended December 31, 2013 and 2012, and the Company’s ending deferred compensation liability as of December 31, 2013 and 2012:
		Year Ended December 31,
		2013				2012
		(in thousands)
	Beginning deferred compensation liability balance	$	966			$	579
	Employee contributions	206				262
	Company matching contributions	115				189
	Distributions	(441		)		(117		)
	Participant earnings (losses)	95				53
	Ending deferred compensation liability balance	$	941			$	966
	Amount to be paid within one year	$	451			$	292
	Remaining balance to be paid beyond one year	$	490			$	674
Deferred Compensation Investment Assets	'
	The following table represents the Company's activity in the investment assets held in the rabbi trust during the years ended December 31, 2013 and 2012:
		Year Ended December 31,
		2013				2012
		(in thousands)
	Beginning investment balance	$	966			$	579
	Investment purchases	321				451
	Distributions	(441		)		(117		)
	Earnings (losses)	95				53
	Ending investment balance	$	941			$	966
Director [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Summary of Nonvested Equity Shares of Common Stock	'
	A summary of the Company’s nonvested equity share units of common stock as of December 31, 2013, 2012 and 2011, and changes during the years then ended, is presented in the table below:
		Year Ended December 31,
		2013							2012					2011
		Shares			Weighted				Shares			Weighted		Shares		Weighted
					Average							Average				Average
					Grant Date							Grant Date Fair				Grant Date Fair
					Fair							Value				Value
					Value
	Outstanding at January 1, 2013	49,185			$	18.5			—			$	—	—		$	—
	Granted (1)	56,464			22.33				58,983			18.83		—		—
	Vested (1)	(49,871	)		18.96				(9,798	)		20.51		—		—
	Forfeited or expired	—			—				—			—		—		—
	Outstanding at December 31, 2013	55,778			$	19.35			49,185			$	18.5	—		$	—

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Schedule of Aggregate Undiscounted Minimum Future Lease Payments	'
	Lease Financing Obligation. The Company has a Lease Financing Obligation with Bank of America Leasing & Capital, LLC as the lead bank as discussed in Note 5. The aggregate undiscounted minimum future lease payments are presented below:
		As of December 31, 2013
		(in thousands)
	2014	$	5,942
	2015	5,942
	2016	5,942
	2017	5,942
	2018	5,942
	Thereafter	9,901
	Total	$	39,611
Gross Future Minimum Transportation Demand and Firm Processing Charges	'
	The amounts in the table below represent the Company’s gross future minimum transportation demand and firm processing charges. However, the Company will record in its financial statements only the Company’s proportionate share based on the Company’s working interest and net revenue interest, which will vary from property to property.
		As of December 31, 2013
		(in thousands)
	2014	$	36,905
	2015	36,717
	2016	35,466
	2017	33,085
	2018	33,521
	Thereafter	63,813
	Total	$	239,507
Future Minimum Annual Payments Under Drilling, Lease and Other Agreements	'
	Future minimum annual payments under lease and other agreements are as follows:
		As of December 31, 2013
		(in thousands)
	2014	$	4,655
	2015 (1)	10,014
	2016	2,678
	2017	2,517
	2018	2,525
	Thereafter	633
	Total (2)	$	23,022
	-1	Includes a drilling carry agreement in the amount of $8.5 million related to acreage in the Powder River Basin. As of December 31, 2013, the Company has satisfied $1.6 million of this carry. The Company will owe the remaining carry balance if not satisfied by October 1, 2015.
	-2	The total includes the lease payments for 19,200 square feet of the Denver office which is under a sublease agreement as of December 31, 2013.

Guarantor_Subsidiaries_Tables

Guarantor Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Schedule of Condensed Consolidating Balance Sheets	'
	Condensed Consolidating Balance Sheets
		As of December 31, 2013
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Assets:
	Current assets	$	154,794		$	2,453		$	—		$	157,247
	Property and equipment, net	2,088,591			113,905			—			2,202,496
	Intercompany receivable (payable)	155,909			(155,909		)	—			—
	Investment in subsidiaries	(44,976		)	—			44,976			—
	Noncurrent assets	21,770			—			—			21,770
	Total assets	$	2,376,088		$	(39,551	)	$	44,976		$	2,381,513
	Liabilities and Stockholders’ Equity:
	Current liabilities	$	192,093		$	626		$	—		$	192,719
	Long-term debt	979,082			—			—			979,082
	Deferred income taxes	159,139			2,187			—			161,326
	Other noncurrent liabilities	40,056			2,612			—			42,668
	Stockholders’ equity	1,005,718			(44,976		)	44,976			1,005,718
	Total liabilities and stockholders’ equity	$	2,376,088		$	(39,551	)	$	44,976		$	2,381,513
		As of December 31, 2012
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Assets:
	Current assets	$	226,013		$	2,326		$	—		$	228,339
	Property and equipment, net	2,514,240			97,097			—			2,611,337
	Intercompany receivable (payable)	141,272			(141,272		)	—			—
	Investment in subsidiaries	(47,533		)	—			47,533			—
	Noncurrent assets	29,773			—			—			29,773
	Total assets	$	2,863,765		$	(41,849	)	$	47,533		$	2,869,449
	Liabilities and Stockholders’ Equity:
	Current liabilities	$	212,117		$	1,016		$	—		$	213,133
	Long-term debt	1,156,654			—			—			1,156,654
	Deferred income taxes	264,113			2,251			—			266,364
	Other noncurrent liabilities	48,106			2,417			—			50,523
	Stockholders’ equity	1,182,775			(47,533		)	47,533			1,182,775
	Total liabilities and stockholders’ equity	$	2,863,765		$	(41,849	)	$	47,533		$	2,869,449
Schedule of Condensed Consolidating Statements of Operations	'
	Condensed Consolidating Statements of Operations
		Year Ended December 31, 2013
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Operating and other revenues	$	536,557		$	31,536		$	—		$	568,093
	Operating expenses	(654,189		)	(28,979		)	—			(683,168		)
	General and administrative	(64,902		)	—			—			(64,902		)
	Interest income and other income (expense)	(131,389		)	—			—			(131,389		)
	Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	(313,923		)	2,557			—			(311,366		)
	Benefit from income taxes	118,633			—			—			118,633
	Equity in earnings (loss) of subsidiaries	2,557			—			(2,557		)	—
	Net income (loss)	$	(192,733	)	$	2,557		$	(2,557	)	$	(192,733	)
		Year Ended December 31, 2012
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Operating and other revenues	$	682,209		$	17,986		$	—		$	700,195
	Operating expenses	(590,185		)	(18,135		)	—			(608,320		)
	General and administrative	(68,666		)	—			—			(68,666		)
	Interest income and other income (expense)	(20,991		)	—			—			(20,991		)
	Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	2,367			(149		)	—			2,218
	Provision for income taxes	(1,636		)	—			—			(1,636		)
	Equity in earnings (loss) of subsidiaries	(149		)	—			149			—
	Net income (loss)	$	582		$	(149	)	$	149		$	582
		Year Ended December 31, 2011
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Operating and other revenues	$	770,106		$	15,518		$	—		$	785,624
	Operating expenses	(541,759		)	(55,430		)	—			(597,189		)
	General and administrative	(66,780		)	—			—			(66,780		)
	Interest and other income (expense)	(73,276		)	—			—			(73,276		)
	Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	88,291			(39,912		)	—			48,379
	Provision for income taxes	(17,672		)	—			—			(17,672		)
	Equity in earnings (loss) of subsidiaries	(39,912		)	—			39,912			—
	Net income (loss)	$	30,707		$	(39,912	)	$	39,912		$	30,707
Schedule of Condensed Consolidating Statements of Comprehensive Income	'
	Condensed Consolidating Statements of Comprehensive Income (Loss)
		Year Ended December 31, 2013
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Net Income (Loss)	$	(192,733	)	$	2,557		$	(2,557	)	$	(192,733	)
	Other Comprehensive Income (Loss), net of tax:
	Effect of derivative financial instruments	(4,663		)	—			—			(4,663		)
	Other comprehensive loss	(4,663		)	—			—			(4,663		)
	Comprehensive Income (Loss)	$	(197,396	)	$	2,557		$	(2,557	)	$	(197,396	)
		Year Ended December 31, 2012
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Net Income (Loss)	$	582		$	(149	)	$	149		$	582
	Other Comprehensive Income (Loss), net of tax:
	Effect of derivative financial instruments	(50,712		)	—			—			(50,712		)
	Other comprehensive loss	(50,712		)	—			—			(50,712		)
	Comprehensive Income (Loss)	$	(50,130	)	$	(149	)	$	149		$	(50,130	)
		Year Ended December 31, 2011
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Net Income (Loss)	$	30,707		$	(39,912	)	$	39,912		$	30,707
	Other Comprehensive Income (Loss), net of tax:
	Effect of derivative financial instruments	8,215			—			—			8,215
	Other comprehensive loss	8,215			—			—			8,215
	Comprehensive Income (Loss)	$	38,922		$	(39,912	)	$	39,912		$	38,922
Schedule of Condensed Consolidating Statements of Cash Flows	'
	Condensed Consolidating Statements of Cash Flows
		Year Ended December 31, 2013
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Cash flows from operating activities	$	240,233		$	25,032		$	—		$	265,265
	Cash flows from investing activities:
	Additions to oil and gas properties, including acquisitions	(407,994		)	(37,485		)	—			(445,479		)
	Additions to furniture, fixtures and other	(2,254		)	—			—			(2,254		)
	Proceeds from sale of properties and other investing activities	310,704			—			—			310,704
	Cash flows from financing activities:
	Proceeds from debt	420,000			—			—			420,000
	Principal and redemption premium payments on debt	(576,422		)	—			—			(576,422		)
	Intercompany transfers	(12,453		)	12,453			—			—
	Other financing activities	3,336			—			—			3,336
	Change in cash and cash equivalents	(24,850		)	—			—			(24,850		)
	Beginning cash and cash equivalents	79,395			50			—			79,445
	Ending cash and cash equivalents	$	54,545		$	50		$	—		$	54,595
		Year Ended December 31, 2012
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Cash flows from operating activities	$	382,164		$	6,272		$	—		$	388,436
	Cash flows from investing activities:
	Additions to oil and gas properties, including acquisitions	(929,370		)	(29,284		)	—			(958,654		)
	Additions to furniture, fixtures and other	(7,231		)	—			—			(7,231		)
	Proceeds from sale of properties and other investing activities	303,818			25,070			—			328,888
	Cash flows from financing activities:
	Proceeds from debt	875,826			—			—			875,826
	Principal and redemption premium payments on debt	(595,386		)	—			—			(595,386		)
	Intercompany transfers	2,058			(2,058		)	—			—
	Other financing activities	(9,765		)	—			—			(9,765		)
	Change in cash and cash equivalents	22,114			—			—			22,114
	Beginning cash and cash equivalents	57,281			50			—			57,331
	Ending cash and cash equivalents	$	79,395		$	50		$	—		$	79,445
		Year Ended December 31, 2011
		Parent			Guarantor			Intercompany			Consolidated
		Issuer			Subsidiaries			Eliminations
		(in thousands)
	Cash flows from operating activities	$	486,579		$	(7,231	)	$	—		$	479,348
	Cash flows from investing activities:
	Additions to oil and gas properties, including acquisitions	(884,099		)	(63,107		)	—			(947,206		)
	Additions to furniture, fixtures and other	(11,556		)	414			—			(11,142		)
	Proceeds from sale of properties and other investing activities	1,702			—			—			1,702
	Cash flows from financing activities:
	Proceeds from debt	800,000			—			—			800,000
	Principal and redemption premium payments on debt	(330,000		)	—			—			(330,000		)
	Intercompany transfers	(69,973		)	69,973			—			—
	Other financing activities	5,938			1			—			5,939
	Change in cash and cash equivalents	(1,409		)	50			—			(1,359		)
	Beginning cash and cash equivalents	58,690			—			—			58,690
	Ending cash and cash equivalents	$	57,281		$	50		$	—		$	57,331

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
			5% Convertible Senior Notes Due 2028 [Member]
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Debt, stated interest rate	'	'	5.00%
Debt maturity date	'	'	'2028
Shares of stock options and nonvested performance-based equity shares of common stock	3,162,436	115,215	'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Summary of Accounts Receivable (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Allowance for doubtful accounts	($21)	($325)
Total accounts receivable	97,586	112,011
Accrued oil, gas and NGL sales [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accounts receivable gross	67,583	69,482
Due from joint interest owners [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accounts receivable gross	23,507	36,300
Other [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accounts receivable gross	$6,517	$6,554

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Net Capitalized Costs and Associated Accumulated Depreciation, Depletion & Amortization and Non Cash Impairments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'	'
Proved properties	$485,427	$387,242
Wells and related equipment and facilities	2,192,754	2,625,891
Support equipment and facilities	177,224	304,914
Materials and supplies	8,518	13,220
Total proved oil and gas properties	2,863,923	3,331,267
Unproved properties	239,925	384,486
Wells and facilities in progress	56,674	72,721
Total unproved oil and gas properties, excluded from amortization	296,599	457,207
Accumulated depreciation, depletion, amortization and impairment	-976,339	-1,203,495
Total oil and gas properties, net	$2,184,183	$2,584,979

Summary_of_Significant_Account6

Summary of Significant Accounting Policies - Net Changes in Capitalized Exploratory Well Costs (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]	'	'	'
Beginning of period	$0	$0	$9,041
Additions to capitalized exploratory well costs pending the determination of proved reserves	0	0	110
Reclassifications to wells, facilities and equipment based on the determination of proved reserves	0	0	-6,179
Exploratory well costs charged to dry hole costs and abandonment expense	0	0	-2,972
End of period	$0	$0	$0

Summary_of_Significant_Account7

Summary of Significant Accounting Policies - Non-Cash Impairment Charges, Included within Impairment, Dry Hole Costs and Abandonment Expense in Consolidated Statements of Operations (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]	'		'		'
Non-cash impairment of oil and gas properties	$226,600,000		'		'
Dry hole costs	1,124,000		21,012,000		13,391,000
Abandonment expense	10,723,000		9,509,000		3,930,000
Total non-cash impairment, dry hole costs and abandonment expense	238,398,000		67,869,000		117,599,000
Proved Oil And Gas Properties [Member]	'		'		'
Summary Of Significant Accounting Policies [Line Items]	'		'		'
Non-cash impairment of oil and gas properties	206,953,000	[1]	0		82,814,000	[2]
Unproved Oil And Gas Properties [Member]	'		'		'
Summary Of Significant Accounting Policies [Line Items]	'		'		'
Non-cash impairment of oil and gas properties	19,598,000	[3]	37,348,000	[4]	17,464,000	[5]
Long Lived Assets Held-for-sale, Impairment Charge	2,500,000		'		'
Unproved properties, no future development plans [Member]	'		'		'
Summary Of Significant Accounting Policies [Line Items]	'		'		'
Non-cash impairment of oil and gas properties	$17,100,000		'		'
[1]	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2013 related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
[2]	Non-cash impairment of proved oil and gas properties for the year ended December 31, 2011 related to properties within the Powder River and Wind River Basins. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.
[3]	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2013 was comprised of $17.1 million related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value and $2.5 million related to our West Tavaputs properties based upon an analysis of the carrying value of the related properties relative to their estimated fair values. These assets were sold in December 2013.
[4]	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2012 related to certain unproved oil and gas properties within exploration projects primarily as a result of unfavorable natural gas exploratory results, unfavorable market conditions or no future plans to evaluate the remaining acreage.
[5]	Non-cash impairment of unproved oil and gas properties for the year ended December 31, 2011 related to certain unproved oil and gas properties within exploration projects primarily as a result of no future plans to evaluate the remaining acreage and an estimated market value below our carrying value.

Summary_of_Significant_Account8

Summary of Significant Accounting Policies - Accounts Payable and Accrued Liabilities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'	'
Accrued drilling, completion and facility costs	$54,750	$42,094
Accrued lease operating, gathering, transportation and processing expenses	17,317	16,862
Accrued general and administrative expenses	14,605	13,054
Trade payables and other	29,256	53,007
Total accounts payable and accrued liabilities	$115,928	$125,017

Summary_of_Significant_Account9

Summary of Significant Accounting Policies - Calculation of Basic and Diluted Earnings (Loss) Per Share (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounting Policies [Abstract]	'	'	'
Net Income (Loss)	($192,733)	$582	$30,707
Basic weighted-average common shares outstanding in period (in shares)	47,496,857	47,194,668	46,535,632
Add dilutive effects of stock options and nonvested equity shares of common stock (in shares)	0	159,000	701,000
Diluted weighted-average common shares outstanding in period (in shares)	47,496,857	47,353,951	47,236,663
Basic net income (loss) per common share (in dollars per share)	($4.06)	$0.01	$0.66
Diluted net income (loss) per common share (in dollars per share)	($4.06)	$0.01	$0.65

Supplemental_Disclosures_of_Ca2

Supplemental Disclosures of Cash Flow Information - Supplemental Cash Flow Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplemental Cash Flow Information [Abstract]	'	'	'
Cash paid for interest, net of amount capitalized	$94,205	$83,718	$36,504
Cash paid for income taxes	1,163	10	-8,128
Supplemental disclosures of non-cash investing and financing activities:	'	'	'
Current liabilities	75,340	49,598	66,257
Net increase (decrease) in asset retirement obligations	-6,996	-25,236	13,185
Treasury stock acquired for employee stock option exercises	0	0	592
Retirement of treasury stock	$1,778	$2,513	$4,436

Divestitures_Additional_Inform

Divestitures - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Proceeds from Divestiture of Businesses	$309.40	$325.30
Asset Impairment Charges	209.5	'
Cash proceeds and recognized pre-tax loss	'	-4.5
Wind River Basin [Member]	'	'
Percentage Of Assets Sold	'	100.00%
Cash proceeds and recognized pre-tax loss	($3.10)	'
Powder River Basin [Member]	'	'
Percentage Of Assets Sold	'	100.00%

Divestitures_Asset_Held_for_Sa

Divestitures - Asset Held for Sale (Details) (USD $)	Dec. 10, 2013
In Thousands, unless otherwise specified
Long Lived Assets Held-for-sale [Line Items]	'
Oil and gas properties held for sale, net	$368,020
Asset retirement obligation held for sale	13,471
Lease financing obligation held for sale	45,190
Total liabilities held for sale	58,661
Net assets	309,359
Proved Oil And Gas Properties [Member]	'
Long Lived Assets Held-for-sale [Line Items]	'
Oil and gas properties held for sale, net	1,058,319
Unproved Oil And Gas Properties [Member]	'
Long Lived Assets Held-for-sale [Line Items]	'
Oil and gas properties held for sale, net	10,598
Furniture and Fixtures [Member]	'
Long Lived Assets Held-for-sale [Line Items]	'
Oil and gas properties held for sale, net	4,380
Other Assets [Member]	'
Long Lived Assets Held-for-sale [Line Items]	'
Oil and gas properties held for sale, net	-706,810
Accumulated depreciation, depletion, amortization and impairment [Member]	'
Long Lived Assets Held-for-sale [Line Items]	'
Oil and gas properties held for sale, net	$1,533

LongTerm_Debt_Outstanding_Debt

Long-Term Debt - Outstanding Debt (Detail) (USD $)

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Jul. 15, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Sep. 27, 2011

Dec. 31, 2013

Dec. 31, 2012

Mar. 12, 2012

Jul. 23, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Amended Credit Facility [Member]

Amended Credit Facility [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Total Debt [Member]

Total Debt [Member]

Current Portion of Long-Term Debt [Member]

Current Portion of Long-Term Debt [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maturity Date

'

'

31-Oct-16

'

15-Jul-16

'

'

15-Mar-28

'

1-Oct-19

'

'

15-Oct-22

'

'

10-Aug-20

10-Aug-20

'

'

'

'

'

Principal

$979,082,000

$1,163,863,000

$115,000,000

[1]

$0

[1]

$0

$250,000,000

$250,000,000

$25,344,000

[2]

$25,344,000

[2]

$400,000,000

$400,000,000

'

$400,000,000

$400,000,000

'

'

$43,329,000

$97,596,000

$983,673,000

$1,172,940,000

$4,591,000

$9,077,000

Unamortized Discount

0

-7,209,000

0

0

0

'

-7,209,000

0

[2]

0

[2]

0

0

'

0

0

'

'

0

0

0

-7,209,000

0

0

Carrying Amount

979,082,000

1,156,654,000

115,000,000

[1]

0

[1]

0

'

242,791,000

[3]

25,344,000

[2],[4]

25,344,000

[2],[4]

400,000,000

[5]

400,000,000

[5]

'

400,000,000

[6]

400,000,000

[6]

'

'

43,329,000

[7]

97,596,000

[7]

983,673,000

1,165,731,000

4,591,000

9,077,000

Debt, stated interest rate

'

'

'

'

9.88%

9.88%

9.88%

'

'

7.63%

7.63%

7.63%

7.00%

7.00%

7.00%

'

'

'

'

'

'

'

Debt, fair value

847,200,000

1,120,700,000

115,000,000

'

'

'

271,900,000

25,100,000

25,300,000

430,200,000

435,000,000

'

417,000,000

413,800,000

'

'

41,700,000

97,700,000

'

'

'

'

Aggregate fair value of convertible notes

'

'

'

'

'

'

'

$25,100,000

$25,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

The recorded value of the Amended Credit Facility approximates its fair value due to its floating rate structure and on financing terms currently available to the Company.

[2]

The Company has the right at any time, with at least 30 days’ notice, to call the Convertible Notes, and the holders have the right to require the Company to purchase the notes on each of March 20, 2015, March 20, 2018 and March 20, 2023.

[3]

The aggregate estimated fair value of the 9.875% Senior Notes was $271.9 million as of December 31, 2012 based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013.

[4]

The aggregate estimated fair value of the Convertible Notes was approximately $25.1 million and $25.3 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.

[5]

The aggregate estimated fair value of the 7.625% Senior Notes was approximately $430.2 million and $435.0 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.

[6]

The aggregate estimated fair value of the 7.0% Senior Notes was approximately $417.0 million and $413.8 million as of December 31, 2013 and 2012, respectively, based on reported market trades of these instruments.

[7]

The aggregate estimated fair value of the Lease Financing Obligation was approximately $41.7 million and $97.7 million as of December 31, 2013 and 2012, respectively. Because there is no active, public market for the Lease Financing Obligation, the aggregate estimated fair value was based on market-based parameters of comparable term secured financing instruments.

LongTerm_Debt_Additional_Infor

Long-Term Debt - Additional Information (Detail) (USD $)

12 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 10, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 20, 2012

Dec. 31, 2013

Mar. 12, 2008

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Jul. 15, 2013

Dec. 31, 2013

Dec. 31, 2012

Sep. 27, 2011

Dec. 31, 2013

Mar. 12, 2012

Dec. 31, 2013

Jul. 23, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Sep. 27, 2011

Dec. 31, 2013

Dec. 31, 2012

Mar. 12, 2012

Minimum [Member]

Maximum [Member]

5% Convertible Senior Notes Due 2028 [Member]

5% Convertible Senior Notes Due 2028 [Member]

5% Convertible Senior Notes Due 2028 [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Amended Credit Facility [Member]

Amended Credit Facility [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

7.625% Senior Notes Due 2019 [Member]

7.0% Senior Notes Due 2022 [Member]

7.0% Senior Notes Due 2022 [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt instrument, maturity date

'

'

'

'

'

'

'

'

'

15-Mar-28

'

31-Oct-16

'

'

15-Jul-16

'

1-Oct-19

15-Oct-22

'

'

10-Aug-20

10-Aug-20

'

1-Oct-19

'

'

15-Oct-22

'

'

Line of credit facility, maximum borrowing capacity

$625,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revolving credit facility, interest rate above London Interbank Offered Rate

'

'

'

'

1.50%

2.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revolving credit facility interest rate percent above LIBOR alternate interest rate

'

'

'

'

0.50%

1.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Commitment fee percentage

'

'

'

'

0.38%

0.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Average annual interest rates incurred on Amended Credit Facility

2.00%

2.20%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of credit facility, maximum amount outstanding during period

'

'

'

'

'

'

'

'

'

'

'

115,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Letters of credit issued amount

'

'

'

'

'

'

'

'

'

'

'

26,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of credit facility, reduced borrowing capacity

484,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal amount

979,082,000

1,163,863,000

'

'

'

'

'

'

172,500,000

'

25,300,000

115,000,000

[1]

0

[1]

250,000,000

0

250,000,000

400,000,000

'

400,000,000

43,329,000

'

43,329,000

97,596,000

400,000,000

400,000,000

'

400,000,000

400,000,000

'

Par value of senior notes

'

'

'

'

'

'

'

'

'

'

'

'

'

104.94%

'

'

103.81%

103.50%

'

'

'

'

'

'

'

'

'

'

'

Repayments of Long-term Debt

'

'

'

'

'

'

'

'

'

'

'

'

'

262,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain (loss) on extinguishment of debt

21,460,000

-1,601,000

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Face Amount of Outstanding Convertible Notes Repaid

'

'

'

'

'

'

147,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of notes put to company

'

'

'

'

'

'

85.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt, stated interest rate

'

'

'

'

'

'

'

5.00%

'

5.00%

5.00%

'

'

9.88%

9.88%

9.88%

7.63%

'

'

'

'

'

'

7.63%

7.63%

7.63%

7.00%

7.00%

7.00%

Debt instrument conversion price rate of redemption

'

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum days notice to call Convertible Notes

'

'

'

'

'

'

'

'

'

'30 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Sale and subsequent lease back

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

100,800,000

'

'

'

'

'

'

'

'

Purchase of equipment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$36,600,000

'

'

'

'

'

'

'

'

Weighted average implicit rate based on interest expense

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3.30%

'

'

'

'

'

'

'

'

Percent of Financing Obligation held-for-sale

'

'

'

51.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

The recorded value of the Amended Credit Facility approximates its fair value due to its floating rate structure and on financing terms currently available to the Company.

LongTerm_Debt_Cash_and_NonCash

Long-Term Debt - Cash and Non-Cash Portion of Interest Expense Related to Long Term Debt (Detail) (USD $)

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Jul. 15, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Sep. 27, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Mar. 12, 2012

Dec. 31, 2013

Dec. 31, 2012

Mar. 12, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Jul. 23, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

5% Convertible Notes [Member]

5% Convertible Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Convertible Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.0% Senior Notes Due 2022 [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

Cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Non-cash interest [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amended Credit Facility interest

'

'

$6,802,000

[1]

$5,652,000

[1]

$5,432,000

[1]

$2,342,000

[1]

$2,342,000

[1]

$2,922,000

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Senior Notes interest

'

'

'

'

'

'

'

'

'

'

'

13,373,000

[2]

24,688,000

[2]

24,688,000

[2]

1,361,000

[2]

2,571,000

[2]

2,485,000

[2]

'

'

'

'

'

'

'

'

'

'

'

'

'

30,500,000

[3]

30,500,000

[3]

7,964,000

[3]

1,070,000

[3]

1,066,000

[3]

332,000

[3]

'

'

'

'

28,000,000

[4]

22,400,000

[4]

0

[4]

795,000

[4]

659,000

[4]

0

[4]

'

'

'

'

'

'

'

'

'

Convertible Notes interest

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,267,000

[5]

2,909,000

[5]

8,625,000

[5]

6,000

[5]

1,771,000

[5]

7,548,000

[5]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Financial Obligation interest

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,852,000

[6]

1,353,000

[6]

0

[6]

30,000

[6]

15,000

[6]

0

[6]

Debt, stated interest rate

'

'

'

'

'

'

'

'

9.88%

9.88%

9.88%

'

'

'

'

'

'

5.00%

'

'

'

'

'

'

'

'

'

7.63%

7.63%

7.63%

'

'

'

'

'

'

'

7.00%

7.00%

7.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Effective interest rate of debt instrument

'

'

'

'

'

'

'

'

'

11.20%

11.20%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8.00%

8.00%

'

'

'

'

'

'

'

'

7.20%

7.20%

'

'

'

'

'

'

'

'

3.30%

'

'

'

'

'

'

Principal

$979,082,000

$1,163,863,000

'

'

'

'

'

'

$0

$250,000,000

$250,000,000

'

'

'

'

'

'

'

$25,300,000

$25,344,000

[7]

$25,344,000

[7]

'

'

'

'

'

'

$400,000,000

$400,000,000

'

'

'

'

'

'

'

$400,000,000

$400,000,000

$400,000,000

'

'

'

'

'

'

'

$43,329,000

$97,596,000

'

'

'

'

'

'

'

[1]

Cash interest includes amounts related to interest and commitment fees paid on the Amended Credit Facility and participation and fronting fees paid on the letter of credit.

[2]

The stated interest rate for the 9.875% Senior Notes was 9.875% per annum with an effective interest rate of 11.2% per annum. The Company redeemed the 9.875% Senior Notes in full on July 15, 2013.

[3]

The stated interest rate for the 7.625% Senior Notes is 7.625% per annum with an effective interest rate of 8.0% per annum.

[4]

The stated interest rate for the 7.0% Senior Notes is 7.0% per annum with an effective interest rate of 7.2% per annum.

[5]

The stated interest rate for the Convertible Notes is 5% per annum. The effective interest rate of the Convertible Notes includes amortization of the debt discount, which represented the fair value of the equity conversion feature at the time of issue. The stated interest rate of 5% on the Convertible Notes will is the effective interest rate of the $25.3 million remaining principal balance, as the related debt discount was fully amortized as of March 31, 2012.

[6]

The effective interest rate for the Lease Financing Obligation is 3.3% per annum.

[7]

The Company has the right at any time, with at least 30 days’ notice, to call the Convertible Notes, and the holders have the right to require the Company to purchase the notes on each of March 20, 2015, March 20, 2018 and March 20, 2023.

Asset_Retirement_Obligations_S

Asset Retirement Obligations - Schedule of Asset Retirement Obligations (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'	'	'
Beginning of period	$47,616	$69,302	$53,079
Liabilities incurred	2,359	4,046	13,186
Liabilities settled	-1,096	-871	-1,046
Disposition of properties	-13,543	-33,560	0
Accretion expense	3,481	4,421	4,083
Revisions to estimate	4,188	4,278	0
End of period	43,005	47,616	69,302
Less: Current asset retirement obligations	3,805	1,566	715
Long-term asset retirement obligations	$39,200	$46,050	$68,587

Fair_Value_Measurements_Balanc

Fair Value Measurements - Balance Sheet Grouping (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Assets	'	'	'	'
Deferred Compensation Plan	$941	$966	'	'
Cash Equivalents - Money Market Funds	54,595	79,445	57,331	58,690
Cash Equivalents - Money Market Funds [Member]	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	53	53	'	'
Commodity Derivatives [Member]	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	11,483	40,432	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	14,771	7,875	'	'
Level 1 [Member]	'	'	'	'
Assets	'	'	'	'
Deferred Compensation Plan	941	966	'	'
Level 1 [Member] | Cash Equivalents - Money Market Funds [Member]	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	53	53	'	'
Level 1 [Member] | Commodity Derivatives [Member]	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	0	0	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	0	0	'	'
Level 2 [Member]	'	'	'	'
Assets	'	'	'	'
Deferred Compensation Plan	0	0	'	'
Level 2 [Member] | Cash Equivalents - Money Market Funds [Member]	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	0	0	'	'
Level 2 [Member] | Commodity Derivatives [Member]	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	11,483	40,432	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	14,771	7,875	'	'
Level 3 [Member]	'	'	'	'
Assets	'	'	'	'
Deferred Compensation Plan	0	0	'	'
Level 3 [Member] | Cash Equivalents - Money Market Funds [Member]	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	0	0	'	'
Level 3 [Member] | Commodity Derivatives [Member]	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	0	0	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	$0	$0	'	'

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)

12 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Jul. 15, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Sep. 27, 2011

Dec. 31, 2013

Dec. 31, 2012

Mar. 12, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

9.875% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.625% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

7.0% Senior Notes [Member]

Amended Credit Facility [Member]

Convertible Notes [Member]

Convertible Notes [Member]

Lease Financing Obligation [Member]

Lease Financing Obligation [Member]

West Tavaputs and Uinta Basin [Member]

Fair Value Measurements [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt, stated interest rate

'

'

9.88%

9.88%

9.88%

7.63%

7.63%

7.63%

7.00%

7.00%

7.00%

'

'

'

'

'

'

Debt, fair value

$847,200,000

$1,120,700,000

'

'

$271,900,000

$430,200,000

$435,000,000

'

$417,000,000

$413,800,000

'

$115,000,000

$25,100,000

$25,300,000

$41,700,000

$97,700,000

'

Non-cash impairment of oil and gas properties

226,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

226,600,000

Long Lived Assets Held-for-sale, Impairment Charge

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$209,500,000

Fair_Value_Measurements_New_De

Fair Value Measurements New (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Estimate of Fair Value, Fair Value Disclosure [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Proved property impairments	$1,937,913	[1]	$2,179,171	[1]
Unproved property impairments	246,270	[1]	405,808	[1]
Fair Value, Inputs, Level 1 [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Proved property impairments	0	[1]	0	[1]
Unproved property impairments	0	[1]	0	[1]
Fair Value, Inputs, Level 2 [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Proved property impairments	0	[1]	0	[1]
Unproved property impairments	0	[1]	0	[1]
Fair Value, Inputs, Level 3 [Member]	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Proved property impairments	206,953	[1]	0	[1]
Unproved property impairments	$19,598	[1]	$37,348	[1]
[1]	See Note 2 for additional details on impairment expense recognized.

Derivative_Instruments_Fair_Va

Derivative Instruments - Fair Value Amounts of Derivative Instruments (Detail) (USD $)	Dec. 31, 2013		Dec. 31, 2012
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Assets	$11,483,000		$40,432,000
Gross Amounts Offset in the Balance Sheet	-8,771,000		-7,471,000
Net Amounts of Assets Presented in the Balance Sheet	2,712,000		32,961,000
Gross Amounts of Recognized Liabilities	-14,771,000		-7,875,000
Gross Amounts Offset in the Balance Sheet	8,771,000		7,471,000
Net Amounts of Liabilities Presented in the Balance Sheet	-6,000,000		-404,000
Balance included in other noncurrent liabilities excluding deferred financing costs and other noncurrent assets	19,200,000		26,800,000
Derivative Financial Instruments, Liabilities [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Balance included in other noncurrent liabilities excluding hedge instruments	3,500,000		4,100,000
Derivative Assets [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Assets	8,259,000		34,828,000
Gross Amounts Offset in the Balance Sheet	-8,086,000	[1]	-4,848,000	[1]
Net Amounts of Assets Presented in the Balance Sheet	173,000		29,980,000
Deferred Financing Costs, Derivative Assets and Other Non Current Assets [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Assets	3,224,000		5,604,000
Gross Amounts Offset in the Balance Sheet	-685,000	[1]	-2,623,000	[1]
Net Amounts of Assets Presented in the Balance Sheet	2,539,000	[2]	2,981,000	[2]
Derivative Liabilities [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Liabilities	-14,074,000		-4,848,000
Gross Amounts Offset in the Balance Sheet	8,086,000	[3]	4,848,000	[3]
Net Amounts of Liabilities Presented in the Balance Sheet	-5,988,000		0
Derivative and Other Non Current Liabilities [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Liabilities	-697,000		-3,027,000
Gross Amounts Offset in the Balance Sheet	685,000	[3]	2,623,000	[3]
Net Amounts of Liabilities Presented in the Balance Sheet	($12,000)		($404,000)	[4]
[1]	Amounts are netted against derivative asset balances with the same counterparty, and therefore, are presented as a net asset on the Consolidated Balance Sheets.
[2]	As of December 31, 2013 and 2012, this line item on the Consolidated Balance Sheets included $19.2 million and $26.8 million of deferred financing costs and other noncurrent assets, respectively.
[3]	Amounts are netted against derivative liability balances with the same counterparty, and therefore are presented as a net liability on the Consolidated Balance Sheets.
[4]	As of December 31, 2013 and 2012, this line item on the Consolidated Balance Sheets includes $3.5 million and $4.1 million of other noncurrent liabilities, respectively.

Derivative_Instruments_Cash_Fl

Derivative Instruments - Cash Flow Hedge Gain and Losses (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'
Amount of Gain (Loss) Recognized in AOCI	$0		$0		$70,636
Amount of Gain (Loss) Reclassified from AOCI into Income (net of tax)	0		0		1,026
Derivatives Qualifying as Cash Flow Hedges	'Commodity Hedges	[1]	'Commodity Hedges	[1]	'Commodity Hedges	[1]
Effect of derivative financial instruments, taxes	-2,802		-30,458		4,886
Commodity Derivatives [Member]	'		'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'
Amount of Gain (Loss) Reclassified from AOCI into Income (net of tax)	$4,663		$50,712	[1],[2]	$62,421	[1],[2]
[1]	Presented net of income tax expense of $2.8 million and $30.5 million and income tax benefit of $4.9 million for the years ended December 31, 2013, 2012 and 2011, respectively.
[2]	Gains reclassified from AOCI into income are included in the oil, gas and NGL production revenues in the Consolidated Statements of Operations.

Derivative_Instruments_Financi

Derivative Instruments - Financial Instruments for Hedging Volume (Detail)	Dec. 31, 2013
	MMBTU
	bbl
2014 [Member]	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Oil (Bbls)	3,211,400
Natural Gas (MMbtu)	24,335,000
Natural Gas Liquids (Bbls)	235,714
2015 [Member]	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Oil (Bbls)	1,348,700
Natural Gas (MMbtu)	3,650,000
Natural Gas Liquids (Bbls)	0
2016 [Member]	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Oil (Bbls)	91,000
Natural Gas (MMbtu)	0
Natural Gas Liquids (Bbls)	0

Derivative_Instruments_Realize

Derivative Instruments - Realized and Unrealized Gains and Losses on Commodity Derivative Instruments (Detail) (Oil and Natural Gas Derivative Instruments [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Oil and Natural Gas Derivative Instruments [Member]	'		'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'
Commodity derivative settlements on derivatives designated as cash flow hedges	$7,463	[1]	$81,166	[1]	$99,922	[1]
Total commodity derivative gain (loss)	($23,068)	[2]	$72,759	[2]	($14,263)	[2]
[1]	Included in oil, gas and NGL production revenues in the Consolidated Statements of Operations.
[2]	Included in commodity derivative gain (loss) in the Consolidated Statements of Operations.

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
	Counterparty
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Number of counterparties for hedges at period end	9

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]	'
U.S. federal income tax rate	35.00%
Federal tax net operating loss carryforwards	$218
Federal AMT credit carryforward	0.7
Net deferred tax liability	161.5
Tax effects reflected in AOCI	0.4
State and Local Jurisdiction [Member]	'
Operating Loss Carryforwards [Line Items]	'
Tax Credit Carryforward, Amount	$5.90

Income_Taxes_Expense_for_Incom

Income Taxes - Expense for Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Income Taxes Expense For Income Taxes [Abstract]	'	'	'
Current Federal	($1,233)	$966	($18)
Current State	-352	886	0
Current Foreign	2	1	2
Deferred Federal	-107,300	100	16,804
Deferred State	-9,750	-317	884
Income tax expense	($118,633)	$1,636	$17,672

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Actual Income Tax Expense (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Income Taxes Reconciliation Of Actual Income Tax Expense [Abstract]	'	'	'
Income tax expense at the federal statutory rate	($108,978)	$777	$16,932
State income taxes, net of federal tax effect	-6,702	-269	1,223
Incentive stock compensation	678	635	-545
Nondeductible political contributions and lobbying costs	96	271	238
Nondeductible officer compensation	138	0	0
Other permanent items	52	26	84
Deferred tax related to the changes in overall state tax rates	-3,851	310	-286
Other, net	-66	-114	26
Income tax expense	($118,633)	$1,636	$17,672

Income_Taxes_Components_of_Def

Income Taxes - Components of Deferred Tax Assets and Deferred Tax Liabilities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Components of Deferred Tax Assets and Liabilities [Abstract]	'	'
Derivative instruments	($89)	($13,108)
Accrued expenses	400	409
Bad debt expense	8	122
Prepaid expenses	-648	-776
Other	130	-399
Total current deferred tax assets (liabilities)	-199	-13,752
Net operating loss carryforward	75,511	39,634
Deferred offering costs	1,243	1,333
Stock-based compensation	14,200	8,117
Deferred rent	962	1,276
Long-term derivative instruments	1,306	878
Minimum tax credit carryforward	688	1,315
Deferred compensation	999	379
State tax credit carryfowards	5,871	4,646
Production payment loan	3,839	8,374
Financing obligation	16,227	36,776
Other	222	0
Less: Valuation allowance	-5,871	-4,646
Total long-term deferred tax assets	115,197	98,082
Oil and gas properties	-276,523	-364,446
Total long-term deferred tax liabilities	-276,523	-364,446
Net long-term deferred tax liabilities	($161,326)	($266,364)

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Oct. 31, 2004
			Series A Junior Participating Preferred Stock [Member]	Series A Junior Participating Preferred Stock [Member]
			Vote
Class of Stock [Line Items]	'	'	'	'
Preferred stock, shares authorized	75,000,000	'	'	'
Preferred stock, par value	$0.00	'	'	$0.00
Common stock, shares authorized	150,000,000	150,000,000	'	'
Common stock, par value	$0.00	$0.00	'	'
Preferred stock designated as Junior Participating Preferred Stock	'	'	'	150,000
Preferred stock, shares outstanding	'	'	0	'
Preferred stock, voting rights	'	'	1,000	'

Stockholders_Equity_Schedule_o

Stockholders' Equity - Schedule of Stockholders Equity (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'
Shares at beginning of period	48,150,475	47,809,903	46,813,269
Exercise of common stock options	259,699	36,560	836,833
Shares issued for 401(k) plan	47,235	41,415	20,913
Shares issued for directors' fees	52,081	12,973	7,636
Shares issued for nonvested equity shares of common stock	1,081,259	454,666	353,716
Shares retired or forfeited	-438,301	-205,042	-222,464
Shares at end of period	49,152,448	48,150,475	47,809,903
Shares at beginning of period	0	0	0
Treasury stock acquired	96,880	92,393	113,715
Treasury stock retired	-96,880	-92,393	-113,715
Shares at end of period	0	0	0

Stockholders_Equity_Schedule_o1

Stockholders Equity - Schedule of Accumulated Other Comprehensive Income (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]	'	'	'
Accumulated other comprehensive income, Gross Beginning	$8,544	$89,714	$76,613
Unrealized change in fair value of hedges, Gross	'	'	113,023
Reclassification adjustment for realized gains on hedges included in net income, Gross	-7,465	-81,170	-99,922
Accumulated other comprehensive income, Gross Ending	1,079	8,544	89,714
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]	'	'	'
Accumulated other comprehensive income, Tax Effect Beginning	-3,212	-33,670	-28,784
Unrealized change in fair value of hedges, Tax Effect	'	'	-42,387
Reclassification adjustment for realized gains on hedges included in net income, Tax Effect	2,802	30,458	37,501
Accumulated other comprehensive income, Tax Effect Ending	-410	-3,212	-33,670
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'	'	'
Accumulated other comprehensive income, Net of Tax Beginning	-5,332	-56,044	-47,829
Unrealized change in fair value of hedges, Net of Tax	'	'	70,636
Reclassification adjustment for realized gains on hedges included in net income, Net of Tax	-4,663	-50,712	-62,421
Accumulated other comprehensive income, Net of Tax Ending	$669	$5,332	$56,044

Equity_Incentive_Compensation_2

Equity Incentive Compensation Plans and Other Employee Benefits - Additional Information (Detail) (USD $)

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2013

31-May-12

Feb. 29, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Feb. 28, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2012

Feb. 28, 2013

Dec. 31, 2013

Feb. 28, 2013

age

Minimum [Member]

Maximum [Member]

2012 Incentive Plan [Member]

2010 Performance Program [Member]

2010 Performance Program [Member]

2010 Performance Program [Member]

2010 Performance Program [Member]

2010 Performance Program (2013 TSR Performance) [Member]

2010 Performance Program (2013 TSR Performance) [Member]

2010 Performance Program (2013 Performance) [Member]

2010 Performance Program (2013 Performance) [Member]

2012 Performance Program [Member]

2012 Performance Program [Member]

2012 Performance Program [Member]

2012 Performance Program [Member]

2013 Performance Program [Member]

2013 Performance Program [Member]

2013 Performance Program [Member]

Market Based Awards [Member]

Maximum [Member]

Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unrecognized compensation cost

$19,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted-average period (years)

'2 years 3 months 18 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum number of shares granted

'

'

'

'

'

'

2,051,402

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate number of shares of common stock subject to options or stock appreciation granted

'

'

'

'

'

'

500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cash incentive awards denominated other than common stock equivalents

'

'

'

'

'

'

5,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expiration period of option granted

'

'

'

'

'

'

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected dividend yield

0.00%

0.00%

0.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted average expected term (in years)

'

'4 years 3 months 18 days

'4 years 6 months

'

'1 month 2 days

'6 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted average expected terms range, minimum period

'4 years 3 months 18 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Weighted Average Expected Term Maximum

'4 years 7 months 6 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of grant's vesting on anniversary date

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Annual compounded forfeiture rate, minimum

'

4.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Annual compounded forfeiture rate, maximum

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of performance-based shares vested in year

'

2,600,000

3,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Options to purchase shares of common stock, Weighted Average Price Per Share

'

$11.02

$12.55

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total intrinsic value of options exercised

500,000

400,000

10,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from stock option exercises

6,385,000

673,000

22,247,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of equity awards

8,100,000

8,600,000

8,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Supplemental grant percentage of performance based shares

'

'

'

'

'

'

'

26.60%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Share based compensation cost related to prior performance goal

'

'

'

'

'

'

'

'

0

200,000

2,400,000

'

'

'

'

'

'

'

'

'

'

'

Additional performance based non-vested equity shares

'

'

'

'

'

'

'

'

'

'

'

22,710

'

'

'

'

'

'

'

'

'

'

Percentage of total grant that will vest for metrics met at stretch level

'

'

'

'

'

'

'

'

'

'

'

'

19.80%

'

'

'

'

'

200.00%

200.00%

'

200.00%

Non-cash stock based compensation

15,634,000

16,370,000

19,396,000

'

'

'

'

'

'

'

'

'

100,000

300,000

'

'

200,000

500,000

'

'

1,600,000

'

Weighted percentage of stockholders return related to performance goals

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

33.30%

'

'

'

33.30%

'

'

Performance goals percentage for change in discretionary cash flows

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

33.30%

'

'

'

33.30%

'

'

Performance goals percentage weight for change in proved properties

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

33.30%

'

'

'

33.30%

'

'

Company's present value discount rate

'

'

'

'

'

'

'

'

'

'

'

'

'

30.00%

'

'

'

'

'

'

'

'

Performance goals percentage weight for proved natural gas and oil reserves per debt adjusted share

'

'

'

'

'

'

'

'

'

'

'

'

'

30.00%

'

'

'

'

'

'

'

'

Performance goals percentage change in discretionary cash flow per debt

'

'

'

'

'

'

'

'

'

'

'

'

'

40.00%

'

'

'

'

'

'

'

'

Shares issued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

86,223

'

'

'

'

'

'

'

Percentage of performance-based awards allowed to vest within a year

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

50.00%

'

'

Percentage of total grant that will vest for metrics met at target level

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

100.00%

'

100.00%

Performance shares set as side at the end of plan

'

179,798

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

450,544

'

Percentage of performance-based awards allowed to vest within a year

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

Maximum number of common stock vest as percentage of performance shares granted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200.00%

'

'

Minimum age for employees to be eligible under employee directed savings plan

21

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of employee's contribution matched by the company

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of employee's pretax income

6.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of common stock matched by company

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cash and common stock contributions

$1,900,000

$2,000,000

$1,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of employee's cash compensation reached under cash matching contributions

'

'

'

6.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity_Incentive_Compensation_3

Equity Incentive Compensation Plans and Other Employee Benefits - Non-Cash Stock-Based Compensation Cost Related to Equity Awards (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Based Compensation [Line Items]	'	'	'
Non-cash stock based compensation	$15,634,000	$16,370,000	$19,396,000
Common Stock Options [Member]	'	'	'
Stock Based Compensation [Line Items]	'	'	'
Non-cash stock based compensation	4,696,000	7,189,000	7,569,000
Nonvested Equity Common Stock [Member]	'	'	'
Stock Based Compensation [Line Items]	'	'	'
Non-cash stock based compensation	7,492,000	7,394,000	8,703,000
Nonvested Equity Common Stock Units [Member]	'	'	'
Stock Based Compensation [Line Items]	'	'	'
Non-cash stock based compensation	1,272,000	708,000	0
Nonvested Performance-Based Equity [Member]	'	'	'
Stock Based Compensation [Line Items]	'	'	'
Non-cash stock based compensation	2,174,000	1,079,000	3,124,000
Performance Based Awards [Member]	'	'	'
Stock Based Compensation [Line Items]	'	'	'
Share based compensation cost related to prior performance goal	$400,000	$200,000	'

Equity_Incentive_Compensation_4

Equity Incentive Compensation Plans and Other Employee Benefits - Fair Value Assumptions and Methodology (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Equity Incentive Compensation Plans And Other Employee Benefits Fair Value Assumptions And Methodology [Abstract]	'	'	'
Weighted average volatility	'	51.00%	55.00%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted average expected term (in years)	'	'4 years 3 months 18 days	'4 years 6 months
Weighted average risk-free rate	'	1.80%	1.90%

Equity_Incentive_Compensation_5

Equity Incentive Compensation Plans and Other Employee Benefits - Summary of Share-Based Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'	'	'
Outstanding at January 1, 2013, Shares	3,020,485	'	'
Granted, Shares	0	'	'
Exercised, Shares	-259,699	-36,560	-836,833
Forfeited or expired, Shares	-1,012,090	'	'
Outstanding at December 31, 2013, Shares	1,748,696	3,020,485	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]	'	'	'
Outstanding at January 1, 2013, Weighted-average Exercise Price	$32.40	'	'
Granted, Weighted-average Exercise Price	$0	'	'
Exercised, Weighted-average Exercise Price	$24.51	'	'
Forfeited or expired, Weighted-average Exercise Price	$33.98	'	'
Outstanding at December 31, 2013, Weighted-average Exercise Price	$32.66	$32.40	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]	'	'	'
Outstanding at December 31, 2013, Weighted-average remaining contractual term	'1 year 5 months 19 days	'	'
Outstanding at December 31, 2013, Aggregate intrinsic value	$1,239,464	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]	'	'	'
Vested, or expected to vest, at December 31, 2013 through the life of the options, Shares	1,718,579	'	'
Vested and exercisable at December 31, 2013, Shares	1,310,201	'	'
Vested, or expected to vest, at December 31, 2013 through the life of the options, Weighted-average Exercise Price	$28.84	'	'
Vested and exercisable at December 31, 2013, Weighted-average Exercise Price	$33.37	'	'
Vested, or expected to vest, at December 31, 2013 through the life of the options, Weighted-average remaining contractual term	'2 years 7 months 2 days	'	'
Vested and exercisable at December 31, 2013, Weighted-average remaining contractual term	'1 year 11 months 16 days	'	'
Vested, or expected to vest, at December 31, 2013 through the life of the options, Aggregate intrinsic value	5,679,748	'	'
Vested and exercisable at December 31, 2013, Aggregate intrinsic value	$1,041,448	'	'

Equity_Incentive_Compensation_6

Equity Incentive Compensation Plans and Other Employee Benefits - Summary of Nonvested Equity Shares of Common Stock (Detail) (Nonvested Equity Common Stock [Member], USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Nonvested Equity Common Stock [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]	'	'	'
Outstanding Beginning, Shares	579,188	639,628	603,521
Granted, Shares	630,715	274,679	346,956
Vested, Shares	-270,482	-241,736	-220,006
Forfeited or expired, Shares	-183,303	-93,383	-90,843
Outstanding Ending, Shares	756,118	579,188	639,628
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]	'	'	'
Outstanding Beginning, Weighted-average Grant Date Fair-Value	$31.02	$35.12	$30.94
Granted, Weighted-average Grant Date Fair-Value	$17.98	$25.62	$39.49
Vested, Weighted-average Grant Date Fair-Value	$29.82	$34.61	$31.83
Forfeited or expired, Weighted-average Grant Date Fair-Value	$24.87	$33.39	$32.03
Outstanding Ending, Weighted-average Grant Date Fair-Value	$22.17	$31.02	$35.12
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]	'	'	'
Vested, or expected to vest, through the life of the awards, Shares	661,224	503,412	578,131
Vested, or expected to vest, through the life of the awards, Weighted-average Grant Date Fair - Value	$22.34	$31.08	$34.94

Equity_Incentive_Compensation_7

Equity Incentive Compensation Plans and Other Employee Benefits - Summary of Nonvested Equity Shares of Common Stock Issued for Payment of Director Fees (Detail) (Director [Member], USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Director [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]	'	'	'
Outstanding Beginning, Shares	49,185	0	0
Granted, Shares	56,464	58,983	0
Vested, Shares	-49,871	-9,798	0
Forfeited or expired, Shares	0	0	0
Outstanding Ending, Shares	55,778	49,185	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]	'	'	'
Outstanding Beginning, Weighted-average Grant Date Fair-Value	$18.50	$0	$0
Granted, Weighted-average Grant Date Fair-Value	$22.33	$18.83	$0
Vested, Weighted-average Grant Date Fair-Value	$18.96	$20.51	$0
Forfeited or expired, Weighted-average Grant Date Fair-Value	$0	$0	$0
Outstanding Ending, Weighted-average Grant Date Fair-Value	$19.35	$18.50	$0

Equity_Incentive_Compensation_8

Equity Incentive Compensation Plans and Other Employee Benefits - Summary of Nonvested Performance-Based Equity Shares of Common Stock (Detail) (Nonvested Performance-Based Equity [Member], USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Nonvested Performance-Based Equity [Member]	'		'		'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]	'		'		'
Outstanding Beginning, Shares	291,606		195,630		287,932
Vested, Shares	0		-64,745		-81,156
Modified, performance goals revised, Shares	-108,933	[1]	-121,191	[1]	-192,821	[1]
Modified, performance goals revised, Shares	108,933	[1]	121,191	[1]	192,821	[1]
Granted, Shares	450,544		179,987		6,760
Forfeited or expired, Shares	-158,118		-19,266		-17,906
Outstanding Ending, Shares	584,032		291,606		195,630
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]	'		'		'
Outstanding Beginning, Weighted-average Grant Date Fair-Value	$26.85		$33.36		$31.76
Vested, Weighted-average Grant Date Fair-Value	$0		$39.90		$32.10
Modified, performance goals revised, Weighted-average Grant Date Fair Value	$27.75	[1]	$39.90	[1]	$32.18	[1]
Modified, performance goals revised, Weighted-average Grant Date Fair Value	$18.18	[1]	$27.75	[1]	$39.88	[1]
Granted, Weighted-average Grant Date Fair-Value	$19.99		$27.57		$40.52
Forfeited or expired, Weighted-average Grant Date Fair-Value	$22.52		$33.82		$30.94
Outstanding Ending, Weighted-average Grant Date Fair-Value	$19.80		$26.85		$33.36
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]	'		'		'
Vested, or expected to vest, through the life of the awards, Shares	522,312		87,522		183,178
Vested, or expected to vest, through the life of the awards, Weighted-average Grant Date Fair - Value	$22.14		$25.33		$33.37
[1]	As the Compensation Committee approved new performance metrics for the vesting of performance shares in the upcoming year, a new grant date was then created for any unvested awards that were granted in previous years, and a new fair value was established for financial reporting purposes.

Equity_Incentive_Compensation_9

Equity Incentive Compensation Plans and Other Employee Benefits - Director Fees (Detail) (Director [Member], USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Director [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Director fees (shares)	16,151	12,973	7,636
Stock-based compensation (in thousands)	$351	$276	$307

Recovered_Sheet1

Equity Incentive Compensation Plans and Other Employee Benefits - Deferred Compensation Liability (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred Compensation Liability [Roll Forward]	'	'
Beginning deferred compensation liability balance	$966	$579
Employee contributions	206	262
Company matching contributions	115	189
Distributions	-441	-117
Participant earnings (losses)	95	53
Ending deferred compensation liability balance	941	966
Deferred Compensation Liability [Abstract]	'	'
Amount to be paid within one year	451	292
Remaining balance to be paid beyond one year	$490	$674

Recovered_Sheet2

Equity Incentive Compensation Plans and Other Employee Benefits - Deferred Compensation Investment Assets (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Compensation Liability [Roll Forward]	'	'
Beginning investment balance	$966	$579
Investment purchases	321	451
Distributions	-441	-117
Earnings (losses)	95	53
Ending investment balance	$941	$966

Significant_Customers_and_Othe1

Significant Customers and Other Concentrations - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Customer	Customer	Customer
Concentration Risk [Line Items]	'	'	'
Number of counterparties of which hedges are in place	9	'	'
Sales Revenue, Product Line [Member] | Customer Concentration Risk [Member]	'	'	'
Concentration Risk [Line Items]	'	'	'
Customers account for production revenues	1	2	3

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Agreement
Contingencies And Commitments [Line Items]	'	'	'
Transportation Demand Charges	$42.60	$45	$35.30
Firm processing charges	4.6	6.2	5
Number of take-or-pay purchase agreements for supply of carbon dioxide	1	'	'
Total financial commitment on take-or-pay purchase agreements for supply of carbon dioxide	1.7	'	'
Office lease expense	$1.80	$2	$1.50
Minimum [Member]	'	'	'
Contingencies And Commitments [Line Items]	'	'	'
Contract term, years	'2 years	'	'
Maximum [Member]	'	'	'
Contingencies And Commitments [Line Items]	'	'	'
Contract term, years	'8 years	'	'

Commitments_and_Contingencies_2

Commitments and Contingencies - Schedule of Aggregate Undiscounted Minimum Future Lease Payments (Detail) (Lease Financing Obligation [Member], USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Lease Financing Obligation [Member]	'
Future Minimum Lease Payments Under Capital Leases And Operating Leases For Continuing Operations [Line Items]	'
2014	$5,942
2015	5,942
2016	5,942
2017	5,942
2018	5,942
Thereafter	9,901
Total	$39,611	[1]
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjFjY2RhMzYxYzc3YTRjZWFiYmZlMmVkM2E2Y2VlMGNlfFRleHRTZWxlY3Rpb246MkMzNzhBQTNGMTYxMDBEOUI1MTkxNDYzQkVCQzIwQjIM}

Commitments_and_Contingencies_3

Commitments and Contingencies - Gross Future Minimum Transportation Demand and Firm Processing Charges (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]	'
2014	$36,905
2015	36,717
2016	35,466
2017	33,085
2018	33,521
Thereafter	63,813
Total	$239,507	[1]
[1]	As of December 31, 2013 (in thousands)2014$36,905201536,717201635,466201733,085201833,521Thereafter63,813Total$239,507

Commitments_and_Contingencies_4

Commitments and Contingencies - Future Minimum Annual Payments under Drilling, Lease and Other Agreements (Detail) (USD $)	Dec. 31, 2013
Office & Equipment Leases	'
Operating Leased Assets [Line Items]	'
2014	$4,655,000
2015	10,014,000
2016	2,678,000
2017	2,517,000
2018	2,525,000
Thereafter	633,000
Total	23,022,000
Property Subject to Operating Lease [Member] | Powder River Basin [Member] | Office & Equipment Leases	'
Operating Leased Assets [Line Items]	'
2015	8,500,000
Amount of carry agreement already satisfied	$1,600,000
Property Subject to Operating Sublease [Member] | Denver Office [Member] | Office Leases [Member]	'
Operating Leased Assets [Line Items]	'
Area of Real Estate Property	19,200

Guarantor_Subsidiaries_Additio

Guarantor Subsidiaries - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Sep. 27, 2011	Dec. 31, 2013	Dec. 31, 2012	Mar. 12, 2012
		7.625% Senior Notes [Member]	7.625% Senior Notes [Member]	7.625% Senior Notes [Member]	7.0% Senior Notes [Member]	7.0% Senior Notes [Member]	7.0% Senior Notes [Member]
Guarantor Subsidiaries [Line Items]	'	'	'	'	'	'	'
Debt, stated interest rate	'	7.63%	7.63%	7.63%	7.00%	7.00%	7.00%
Percentage of Guarantor Subsidiaries	100.00%	'	'	'	'	'	'

Guarantor_Subsidiaries_Schedul

Guarantor Subsidiaries - Schedule of Condensed Consolidating Balance Sheets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Assets:	'	'	'	'
Current assets	$157,247	$228,339	'	'
Property and equipment, net	2,202,496	2,611,337	'	'
Intercompany receivable (payable)	0	0	'	'
Investment in subsidiaries	0	0	'	'
Noncurrent assets	21,770	29,773	'	'
Total	2,381,513	2,869,449	'	'
Liabilities and Stockholders’ Equity:	'	'	'	'
Current liabilities	192,719	213,133	'	'
Long-term debt	979,082	1,156,654	'	'
Deferred income taxes	161,326	266,364	'	'
Other noncurrent liabilities	42,668	50,523	'	'
Stockholders’ equity	1,005,718	1,182,775	1,218,838	1,140,962
Total	2,381,513	2,869,449	'	'
Parent Issuer [Member]	'	'	'	'
Assets:	'	'	'	'
Current assets	154,794	226,013	'	'
Property and equipment, net	2,088,591	2,514,240	'	'
Intercompany receivable (payable)	155,909	141,272	'	'
Investment in subsidiaries	-44,976	-47,533	'	'
Noncurrent assets	21,770	29,773	'	'
Total	2,376,088	2,863,765	'	'
Liabilities and Stockholders’ Equity:	'	'	'	'
Current liabilities	192,093	212,117	'	'
Long-term debt	979,082	1,156,654	'	'
Deferred income taxes	159,139	264,113	'	'
Other noncurrent liabilities	40,056	48,106	'	'
Stockholders’ equity	1,005,718	1,182,775	'	'
Total	2,376,088	2,863,765	'	'
Guarantor Subsidiaries [Member]	'	'	'	'
Assets:	'	'	'	'
Current assets	2,453	2,326	'	'
Property and equipment, net	113,905	97,097	'	'
Intercompany receivable (payable)	-155,909	-141,272	'	'
Investment in subsidiaries	0	0	'	'
Noncurrent assets	0	0	'	'
Total	-39,551	-41,849	'	'
Liabilities and Stockholders’ Equity:	'	'	'	'
Current liabilities	626	1,016	'	'
Long-term debt	0	0	'	'
Deferred income taxes	2,187	2,251	'	'
Other noncurrent liabilities	2,612	2,417	'	'
Stockholders’ equity	-44,976	-47,533	'	'
Total	-39,551	-41,849	'	'
Intercompany Eliminations [Member]	'	'	'	'
Assets:	'	'	'	'
Current assets	0	0	'	'
Property and equipment, net	0	0	'	'
Intercompany receivable (payable)	0	0	'	'
Investment in subsidiaries	44,976	47,533	'	'
Noncurrent assets	0	0	'	'
Total	44,976	47,533	'	'
Liabilities and Stockholders’ Equity:	'	'	'	'
Current liabilities	0	0	'	'
Long-term debt	0	0	'	'
Deferred income taxes	0	0	'	'
Other noncurrent liabilities	0	0	'	'
Stockholders’ equity	44,976	47,533	'	'
Total	$44,976	$47,533	'	'

Guarantor_Subsidiaries_Schedul1

Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Operations (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]	'	'	'
Operating and other revenues	$568,093	$700,195	$785,624
Operating expenses	-683,168	-608,320	-597,189
General and administrative	-64,902	-68,666	-66,780
Interest income and other income (expense)	-131,389	-20,991	-73,276
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	-311,366	2,218	48,379
Benefit from income taxes	118,633	-1,636	-17,672
Equity in earnings (loss) of subsidiaries	0	0	0
Net income (loss)	-192,733	582	30,707
Parent Issuer [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Operating and other revenues	536,557	682,209	770,106
Operating expenses	-654,189	-590,185	-541,759
General and administrative	-64,902	-68,666	-66,780
Interest income and other income (expense)	-131,389	-20,991	-73,276
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	-313,923	2,367	88,291
Benefit from income taxes	118,633	-1,636	-17,672
Equity in earnings (loss) of subsidiaries	2,557	-149	-39,912
Net income (loss)	-192,733	582	30,707
Guarantor Subsidiaries [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Operating and other revenues	31,536	17,986	15,518
Operating expenses	-28,979	-18,135	-55,430
General and administrative	0	0	0
Interest income and other income (expense)	0	0	0
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	2,557	-149	-39,912
Benefit from income taxes	0	0	0
Equity in earnings (loss) of subsidiaries	0	0	0
Net income (loss)	2,557	-149	-39,912
Intercompany Eliminations [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Operating and other revenues	0	0	0
Operating expenses	0	0	0
General and administrative	0	0	0
Interest income and other income (expense)	0	0	0
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	0	0	0
Benefit from income taxes	0	0	0
Equity in earnings (loss) of subsidiaries	-2,557	149	39,912
Net income (loss)	($2,557)	$149	$39,912

Guarantor_Subsidiaries_Schedul2

Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Comprehensive Income (Loss) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]	'	'	'
Net Income (Loss)	($192,733)	$582	$30,707
Effect of derivative financial instruments	-4,663	-50,712	8,215
Other comprehensive loss	-4,663	-50,712	8,215
Comprehensive Income (Loss)	-197,396	-50,130	38,922
Parent Issuer [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Net Income (Loss)	-192,733	582	30,707
Effect of derivative financial instruments	-4,663	-50,712	8,215
Other comprehensive loss	-4,663	-50,712	8,215
Comprehensive Income (Loss)	-197,396	-50,130	38,922
Guarantor Subsidiaries [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Net Income (Loss)	2,557	-149	-39,912
Effect of derivative financial instruments	0	0	0
Other comprehensive loss	0	0	0
Comprehensive Income (Loss)	2,557	-149	-39,912
Intercompany Eliminations [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Net Income (Loss)	-2,557	149	39,912
Effect of derivative financial instruments	0	0	0
Other comprehensive loss	0	0	0
Comprehensive Income (Loss)	($2,557)	$149	$39,912

Guarantor_Subsidiaries_Schedul3

Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Cash Flows (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]	'	'	'
Cash flows from operating activities	$265,265	$388,436	$479,348
Cash flows from investing activities:	'	'	'
Additions to oil and gas properties, including acquisitions	-445,479	-958,654	-947,206
Additions to furniture, fixtures and other	-2,254	-7,231	-11,142
Proceeds from sale of properties and other investing activities	310,704	328,888	1,702
Cash flows from financing activities:	'	'	'
Proceeds from debt	420,000	875,826	800,000
Principal and redemption premium payments on debt	-576,422	-595,386	-330,000
Intercompany transfers	0	0	0
Other financing activities	3,336	-9,765	5,939
Increase (Decrease) in Cash and Cash Equivalents	-24,850	22,114	-1,359
Beginning Cash and Cash Equivalents	79,445	57,331	58,690
Ending Cash and Cash Equivalents	54,595	79,445	57,331
Parent Issuer [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Cash flows from operating activities	240,233	382,164	486,579
Cash flows from investing activities:	'	'	'
Additions to oil and gas properties, including acquisitions	-407,994	-929,370	-884,099
Additions to furniture, fixtures and other	-2,254	-7,231	-11,556
Proceeds from sale of properties and other investing activities	310,704	303,818	1,702
Cash flows from financing activities:	'	'	'
Proceeds from debt	420,000	875,826	800,000
Principal and redemption premium payments on debt	-576,422	-595,386	-330,000
Intercompany transfers	-12,453	2,058	-69,973
Other financing activities	3,336	-9,765	5,938
Increase (Decrease) in Cash and Cash Equivalents	-24,850	22,114	-1,409
Beginning Cash and Cash Equivalents	79,395	57,281	58,690
Ending Cash and Cash Equivalents	54,545	79,395	57,281
Guarantor Subsidiaries [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Cash flows from operating activities	25,032	6,272	-7,231
Cash flows from investing activities:	'	'	'
Additions to oil and gas properties, including acquisitions	-37,485	-29,284	-63,107
Additions to furniture, fixtures and other	0	0	414
Proceeds from sale of properties and other investing activities	0	25,070	0
Cash flows from financing activities:	'	'	'
Proceeds from debt	0	0	0
Principal and redemption premium payments on debt	0	0	0
Intercompany transfers	12,453	-2,058	69,973
Other financing activities	0	0	1
Increase (Decrease) in Cash and Cash Equivalents	0	0	50
Beginning Cash and Cash Equivalents	50	50	0
Ending Cash and Cash Equivalents	50	50	50
Intercompany Eliminations [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Cash flows from operating activities	0	0	0
Cash flows from investing activities:	'	'	'
Additions to oil and gas properties, including acquisitions	0	0	0
Additions to furniture, fixtures and other	0	0	0
Proceeds from sale of properties and other investing activities	0	0	0
Cash flows from financing activities:	'	'	'
Proceeds from debt	0	0	0
Principal and redemption premium payments on debt	0	0	0
Intercompany transfers	0	0	0
Other financing activities	0	0	0
Increase (Decrease) in Cash and Cash Equivalents	0	0	0
Beginning Cash and Cash Equivalents	0	0	0
Ending Cash and Cash Equivalents	$0	$0	$0