Bill Barrett (BBG) Inactive 10-Q31 Oct 132013 Q3 Quarterly reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2013	Oct. 18, 2013
Document Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'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	'	48,985,749

CONSOLIDATED_BALANCE_SHEETS_UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:	'	'
Cash and cash equivalents	$60,530	$79,445
Accounts receivable, net of allowance for doubtful accounts	99,537	112,011
Derivative assets	3,506	29,980
Prepayments and other current assets	5,478	6,903
Total current assets	169,051	228,339
Property and equipment - at cost, successful efforts method for oil and gas properties:	'	'
Proved oil and gas properties	2,675,696	3,331,267
Unproved oil and gas properties, excluded from amortization	362,386	457,207
Oil and gas properties held for sale, net	382,554	0
Furniture, equipment and other	42,252	45,636
Property, plant and equipment, gross	3,462,888	3,834,110
Accumulated depreciation, depletion, amortization and impairment	-929,743	-1,222,773
Total property and equipment, net	2,533,145	2,611,337
Deferred financing costs and other noncurrent assets	24,065	29,773
Total Assets	2,726,261	2,869,449
Current liabilities:	'	'
Accounts payable and accrued liabilities	123,409	125,017
Amounts payable to oil and gas property owners	22,367	19,663
Production taxes payable	41,803	45,624
Derivative liabilities	2,271	0
Deferred income taxes	11,833	13,752
Current portion of long-term debt	4,554	9,077
Total current liabilities	206,237	213,133
Long-term debt	1,255,243	1,156,654
Asset retirement obligations	38,292	46,050
Liabilities associated with assets held for sale	59,445	0
Deferred income taxes	156,034	266,364
Derivatives and other noncurrent liabilities	4,012	4,473
Stockholdersâ€™ equity:	'	'
Common stock, $0.001 par value; authorized 150,000,000 shares; 48,985,320 and 48,150,475 shares issued and outstanding at September 30, 2013 and December 31, 2012, respectively, with 1,393,438 and 870,794 shares subject to restrictions, respectively	48	47
Additional paid-in capital	897,367	883,923
Retained earnings	107,939	293,473
Treasury stock, at cost: zero shares at September 30, 2013 and December 31, 2012, respectively	0	0
Accumulated other comprehensive income	1,644	5,332
Total stockholdersâ€™ equity	1,006,998	1,182,775
Total liabilities and stockholders' equity	$2,726,261	$2,869,449

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	48,985,320	48,150,475
Common stock, shares outstanding	48,985,320	48,150,475
Common stock, shares subject to restrictions	1,393,438	870,794
Treasury stock, shares	0	0

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating and Other Revenues:	'	'	'	'
Oil, gas and NGL production	$149,345	$180,024	$424,130	$516,556
Other	-790	842	5,001	3,838
Total operating and other revenues	148,555	180,866	429,131	520,394
Operating Expenses:	'	'	'	'
Lease operating expense	18,280	17,003	53,138	54,671
Gathering, transportation and processing expense	16,374	26,725	50,734	79,939
Production tax expense	8,183	8,094	21,915	21,193
Exploration expense	-24	3,562	212	8,063
Impairment, dry hole costs and abandonment expense	219,363	38,540	227,646	60,179
Depreciation, depletion and amortization	72,047	91,392	214,792	251,417
General and administrative expense	14,402	17,965	48,257	51,441
Total operating expenses	348,625	203,281	616,694	526,903
Operating Loss	-200,070	-22,415	-187,563	-6,509
Other Income and Expense:	'	'	'	'
Interest and other income	52	53	123	128
Interest expense	-20,078	-24,527	-69,346	-70,029
Commodity derivative gain (loss)	-25,595	-38,340	-18,607	53,431
Gain (loss) on extinguishment of debt	-21,460	0	-21,460	1,601
Total other income and expense	-67,081	-62,814	-109,290	-14,869
Loss before Income Taxes	-267,151	-85,229	-296,853	-21,378
Benefit from Income Taxes	-100,495	-32,603	-111,319	-7,943
Net Loss	($166,656)	($52,626)	($185,534)	($13,435)
Net Loss Per Common Share, Basic	($3.51)	($1.11)	($3.91)	($0.28)
Net Loss Per Common Share, Diluted	($3.51)	($1.11)	($3.91)	($0.28)
Weighted Average Common Shares Outstanding, Basic	47,535,124	47,230,473	47,452,865	47,172,656
Weighted Average Common Shares Outstanding, Diluted	47,535,124	47,230,473	47,452,865	47,172,656

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Statement of Other Comprehensive Income [Abstract]	'	'	'	'	'
Net Loss	($166,656)	($52,626)	($185,534)	($13,435)	$582
Other Comprehensive Loss, net of tax:	'	'	'	'	'
Effect of derivative financial instruments	-1,186	-12,739	-3,688	-41,644	-50,712
Other comprehensive loss	-1,186	-12,739	-3,688	-41,644	'
Comprehensive Loss	($167,842)	($65,365)	($189,222)	($55,079)	'

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Operating Activities:	'	'
Net Loss	($185,534)	($13,435)
Adjustments to reconcile to net cash provided by operations:	'	'
Depreciation, depletion and amortization	214,792	251,417
Deferred income tax benefit	-110,036	-7,669
Impairment, dry hole costs and abandonment expense	227,646	60,179
Total commodity derivative (gain) loss	18,607	-53,431
Settlements of commodity derivatives	2,971	35,014
Stock compensation and other non-cash charges	12,681	14,249
Amortization of debt discounts and deferred financing costs	4,535	6,710
(Gain) loss on extinguishment of debt	21,460	-1,601
Gain on sale of properties	-3,102	-108
Change in operating assets and liabilities:	'	'
Accounts receivable	12,343	4,475
Prepayments and other assets	1,475	1,515
Accounts payable, accrued and other liabilities	-24,801	-4,813
Amounts payable to oil and gas property owners	6,510	567
Production taxes payable	-3,245	-2,466
Net cash provided by operating activities	196,302	290,603
Investing Activities:	'	'
Additions to oil and gas properties, including acquisitions	-335,597	-751,545
Additions of furniture, equipment and other	-1,506	-5,519
Proceeds from sale of properties and other investing activities	784	91
Net cash used in investing activities	-336,319	-756,973
Financing Activities:	'	'
Proceeds from debt	390,000	785,826
Principal and redemption premium payments on debt	-269,125	-343,163
Proceeds from stock option exercises	1,653	672
Deferred financing costs and other	-1,426	-10,363
Net cash provided by financing activities	121,102	432,972
Decrease in Cash and Cash Equivalents	-18,915	-33,398
Beginning Cash and Cash Equivalents	79,445	57,331
Ending Cash and Cash Equivalents	$60,530	$23,933

CONSOLIDATED_STATEMENTS_OF_STO

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) (USD $)	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income
In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income
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	0	673	0	-2,513	0
APIC pool for excess tax benefits related to share-based compensation	32	0	32	0	0	0
Stock-based compensation	16,874	0	16,874	0	0	0
Retirement of treasury stock	0	0	-2,513	0	2,513	0
Settlement of convertible notes	-999	0	-999	0	0	0
Net income (loss)	582	0	0	582	0	0
Effect of derivative financial instruments, net of taxes	-50,712	0	0	0	0	-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	238	1	1,652	0	-1,415	0
Stock-based compensation	13,207	0	13,207	0	0	0
Retirement of treasury stock	0	0	-1,415	0	1,415	0
Net income (loss)	-185,534	0	0	-185,534	0	0
Effect of derivative financial instruments, net of taxes	-3,688	0	0	0	0	-3,688
Balance at Sep. 30, 2013	$1,006,998	$48	$897,367	$107,939	$0	$1,644

CONSOLIDATED_STATEMENTS_OF_STO1

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Statement of Stockholders' Equity [Abstract]	'	'	'	'	'
Effect of derivative financial instruments, taxes	$700	$7,700	$2,216	$25,000	$30,458

Organization

Organization	9 Months Ended
Organization	Sep. 30, 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 crude oil, natural gas and natural gas liquids (“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	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	Summary of Significant Accounting Policies
	Basis of Presentation. The accompanying unaudited 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. In the opinion of management, the accompanying financial statements include all adjustments (consisting of normal recurring accruals and adjustments) necessary to present fairly, in all material respects, the Company’s interim results. However, operating results for the periods presented are not necessarily indicative of the results that may be expected for the full year.
	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 undeveloped 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 September 30, 2013				As of December 31, 2012
		(in thousands)
	Accrued oil, gas and NGL sales	$	68,013			$	69,482

	Due from joint interest owners	28,489				36,300

	Other	3,058				6,554

	Allowance for doubtful accounts	(23		)		(325		)
	Total accounts receivable	$	99,537			$	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 Unaudited 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 Unaudited 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 September 30, 2013				As of December 31, 2012
		(in thousands)
	Proved properties	$	422,083			$	387,242

	Wells and related equipment and facilities	2,080,178				2,625,891

	Support equipment and facilities	163,242				304,914

	Materials and supplies	10,193				13,220

	Total proved oil and gas properties	$	2,675,696			$	3,331,267

	Unproved properties	307,557				384,486

	Wells and facilities in progress	54,829				72,721

	Total unproved oil and gas properties, excluded from amortization	$	362,386			$	457,207

	Oil and gas properties held for sale, net (1)	378,449				—

	Accumulated depreciation, depletion, amortization and impairment	(907,222		)		(1,203,495		)
	Total oil and gas properties, net	$	2,509,309			$	2,584,979


	-1	The oil and gas properties held for sale balance shown in this table is different from the balance on the Unaudited Consolidated Balance Sheet because it does not include $4.1 million of furniture, equipment and other, net.
	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. As of September 30, 2013 and December 31, 2012, there were no exploratory well costs that had been capitalized for a period greater than one year since the completion of drilling.
	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 Company has no guarantee that the undiscounted future cash flows analysis of its proved property represents the applicable market value. 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 Unaudited Consolidated Statements of Operations, as follows:



		Three Months Ended September 30,								Nine Months Ended September 30,
		2013				2012				2013			2012
		(in thousands)
Non-cash impairment of proved oil and gas properties (1)	$	198,787			$	—			$	198,787		$	—

Non-cash impairment of unproved oil and gas properties (2) (3)	17,777				18,772				17,777			37,109

Dry hole costs	(36		)		15,658				928			15,891

Abandonment expense	2,835				4,110				10,154			7,179

Total non-cash impairment, dry hole costs and abandonment expense	$	219,363			$	38,540			$	227,646		$	60,179



-1	Non-cash impairment of proved oil and gas properties for the three and nine months ended September 30, 2013 related to assets classified as held for sale at September 30, 2013. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.

-2	Non-cash impairment of unproved oil and gas properties for the three and nine months ended September 30, 2013 was comprised of $15.3 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 unproved properties held for sale at September 30, 2013.

-3	Non-cash impairment of unproved oil and gas properties for the three months ended September 30, 2012 of $18.8 million 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. The additional $18.3 million unproved oil and gas properties impairment expense for the nine months ended September 30, 2012 also related to unproved oil and gas properties within other exploration and development projects primarily as a result of unfavorable market conditions or no future plans to evaluate the remaining acreage.
The provision for DD&A of oil and gas properties is calculated on a field-by-field basis using the unit-of-production method. Oil and NGLs are converted to natural gas equivalents, Mcfe, at the standard rate of one barrel to six Mcfe. 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 September 30, 2013				As of December 31, 2012
	(in thousands)
Accrued drilling, completion and facility costs	$	63,618			$	42,094

Accrued lease operating, gathering, transportation and processing expenses	19,481				16,862

Accrued general and administrative expenses	8,542				13,054

Trade payables and other	31,768				53,007

Total accounts payable and accrued liabilities	$	123,409			$	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 crude 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 September 30, 2013 and December 31, 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 Unaudited 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 loss per common share is calculated by dividing net loss attributable to common stock by the weighted average number of common shares outstanding during each period. Diluted net loss per common share is calculated by dividing net 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 three and nine months ended September 30, 2013 and 2012.

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 September 30, 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 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. The Convertible Notes have not been dilutive since their issuance in March 2008 and, therefore, did not impact the diluted net loss per common share calculation for the three and nine months ended September 30, 2013 and 2012. The diluted net loss per common share excludes the anti-dilutive effect of 2,450,539 and 3,799,612 shares of stock options and nonvested equity shares of common stock for the three months ended September 30, 2013 and 2012, respectively, and 2,731,578 and 3,829,825 shares of stock options and nonvested equity shares of common stock for the nine months ended September 30, 2013 and 2012, respectively.
The following table sets forth the calculation of basic and diluted loss per share:



	Three Months Ended September 30,								Nine Months Ended September 30,
	2013				2012				2013			2012
	(in thousands, except per share amounts)
Net loss	$	(166,656	)		$	(52,626	)		$	(185,534	)	$	(13,435	)
Basic weighted-average common shares outstanding in period	47,535				47,230				47,453			47,173

Add dilutive effects of stock options and nonvested equity shares of common stock	—				—				—			—

Diluted weighted-average common shares outstanding in period	47,535				47,230				47,453			47,173

Basic net loss per common share	$	(3.51	)		$	(1.11	)		$	(3.91	)	$	(0.28	)
Diluted net loss per common share	$	(3.51	)		$	(1.11	)		$	(3.91	)	$	(0.28	)
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.

Supplemental_Disclosures_of_Ca

Supplemental Disclosures of Cash Flow Information	9 Months Ended
	Sep. 30, 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:


		Nine Months Ended September 30,
		2013			2012
		(in thousands)
	Cash paid for interest, net of amount capitalized	$	61,796		$	49,040

	Cash paid for income taxes	1,861			11

	Supplemental disclosures of non-cash investing and financing activities:
	Current liabilities	75,265			75,092

	Net increase in asset retirement obligations	2,924			280

	Retirement of treasury stock	(1,415		)	(2,430		)

Divestitures_and_Assets_Held_f

Divestitures and Assets Held for Sale	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]	'
Disposal Groups Excluding Discontinued Operations Disclosure [Text Block]	'
	Divestitures and Assets Held For Sale
	Divestitures
	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. The final 2012 Divestiture proceeds are subject to various purchase price adjustments incurred in the normal course of business and will be finalized during 2013.
	Assets Held for Sale
	During the third quarter of 2013, the Company began marketing the West Tavaputs natural gas assets in the Uinta Basin. Therefore, the related assets and liabilities were classified as held for sale on the Unaudited Consolidated Balance Sheet as of September 30, 2013. Upon the classification as held for sale, the carrying value of the related properties was analyzed in relation to the estimated fair value. As a result, we recognized $198.8 million of proved property impairment expense and $2.5 million of unproved property impairment expense during the three months ended September 30, 2013. As part of the previously announced sale of the West Tavaputs natural gas assets in the Uinta Basin (the “West Tavaputs Sale”), the purchaser will assume approximately 51% of the Company's lease financing arrangement with Bank of America Leasing & Capital, LLC as the lead bank that relates to compressor units on the West Tavaputs property (the “Lease Financing Obligation”.) See the table below for detail of the assets held for sale included on the Unaudited Consolidated Balance Sheet:


		As of September 30, 2013
		(in thousands)
	Assets
	Proved properties	$	1,070,400

	Unproved properties	12,469

	Furniture, equipment and other	4,205

	Accumulated depreciation, depletion, amortization and impairment	(704,520		)
	Total assets held for sale	$	382,554


	Liabilities
	Asset retirement obligation held for sale	13,082

	Lease financing obligation held for sale	46,363

	Total liabilities held for sale	$	59,445


	Net assets	$	323,109

LongTerm_Debt

Long-Term Debt	9 Months Ended
Long-Term Debt	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Long-Term Debt	'
	Long-Term Debt
	The Company’s outstanding debt is summarized below:



			As of September 30, 2013												As of December 31, 2012
		Maturity Date	Principal				Unamortized				Carrying				Principal		Unamortized			Carrying
		Maturity Date	Principal				Discount				Amount				Principal		Discount			Amount
			(in thousands)
	Amended Credit Facility (1)	October 31, 2016	$	390,000			$	—			$	390,000			$	—	$	—		$	—
	Amended Credit Facility (1)	October 31, 2016	$	390,000			$	—			$	390,000			$	—	$	—		$	—
	9.875% Senior Notes (2)	July 15, 2016	—				—				—				250,000		(7,209		)	242,791
	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
	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
	7.625% 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
	7.0% Senior Notes (6)	October 15, 2022	400,000				—				400,000				400,000		—			400,000
	Lease Financing Obligation (7)	August 10, 2020	44,453				—				44,453				97,596		—			97,596
	Lease Financing Obligation (7)	August 10, 2020	44,453				—				44,453				97,596		—			97,596
	Total Debt		$	1,259,797			$	—			$	1,259,797			$	1,172,940	$	(7,209	)	$	1,165,731
	Total Debt		$	1,259,797			$	—			$	1,259,797			$	1,172,940	$	(7,209	)	$	1,165,731
	Less: Current Portion of Long-Term Debt		4,554				—				4,554				9,077		—			9,077
	Less: Current Portion of Long-Term Debt		4,554				—				4,554				9,077		—			9,077
	Total Long-Term Debt (8)		$	1,255,243			$	—			$	1,255,243			$	1,163,863	$	(7,209	)	$	1,156,654
	Total Long-Term Debt (8)		$	1,255,243			$	—			$	1,255,243			$	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.

	-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 $25.2 million and $25.3 million as of September 30, 2013 and December 31, 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 $410.0 million and $435.0 million as of September 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

	-6	The aggregate estimated fair value of the 7.0% Senior Notes was approximately $390.0 million and $413.8 million as of September 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

	-7	The aggregate estimated fair value of the full Lease Financing Obligation was approximately $88.1 million as of September 30, 2013, 51% of which is held for sale at September 30, 2013, and $97.7 million as of December 31, 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.

	-8	The total long-term debt balance excludes $46.4 million related to the Lease Financing Obligation that is included in liabilities associated with assets held for sale in the Unaudited Consolidated Balance Sheet. See Note 4 for additional information.

	Amended Credit Facility
	The Company’s Amended Credit Facility has a maturity date of October 31, 2016 and current commitments and borrowing base of $825.0 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 was 2.1% and 1.8% for the three months ended September 30, 2013 and 2012, and 2.0% and 1.9% for the nine months ended September 30, 2013 and 2012, respectively.
	The borrowing base is required to be re-determined twice per year. On October 25, 2013, the borrowing base was redetermined at $825.0 million based on mid-year reserves and hedge position. The borrowing base will be reduced upon closing of the West Tavaputs Sale, as discussed in Note 13. Future borrowing bases 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 September 30, 2013, the Company had $390.0 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 borrowing capacity of the Amended Credit Facility to $409.0 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 three and nine months ended September 30, 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 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
	In July, 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 11 for discussion of aggregate minimum future lease payments. As part of the West Tavaputs Sale, the purchaser will assume approximately 51% of the Lease Financing Obligation, including the buy-out options. See Note 13.
	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:



	Three Months Ended September 30,								Nine Months Ended September 30,
	2013				2012				2013				2012
	(in thousands)
Amended Credit Facility (1)
Cash interest	$	2,296			$	1,453			$	4,211			$	3,707
Cash interest	$	2,296			$	1,453			$	4,211			$	3,707
Non-cash interest	$	585			$	586			$	1,756			$	1,757
Non-cash interest	$	585			$	586			$	1,756			$	1,757
9.875% Senior Notes (2)
Cash interest	$	1,029			$	6,172			$	13,373			$	18,516
Cash interest	$	1,029			$	6,172			$	13,373			$	18,516
Non-cash interest	$	—			$	657			$	1,361			$	1,911
Non-cash interest	$	—			$	657			$	1,361			$	1,911
Convertible Notes (3)
Cash interest	$	310			$	317			$	943			$	2,585
Cash interest	$	310			$	317			$	943			$	2,585
Non-cash interest	$	1			$	1			$	4			$	1,770
Non-cash interest	$	1			$	1			$	4			$	1,770
7.625% Senior Notes (4)
Cash interest	$	7,625			$	7,625			$	22,875			$	22,875
Cash interest	$	7,625			$	7,625			$	22,875			$	22,875
Non-cash interest	$	272			$	262			$	798			$	803
Non-cash interest	$	272			$	262			$	798			$	803
7.0% Senior Notes (5)
Cash interest	$	7,000			$	7,000			$	21,000			$	15,397
Cash interest	$	7,000			$	7,000			$	21,000			$	15,397
Non-cash interest	$	203			$	197			$	592			$	464
Non-cash interest	$	203			$	197			$	592			$	464
Lease Financing Obligation (6)
Cash interest	$	750			$	548			$	2,305			$	548
Cash interest	$	750			$	548			$	2,305			$	548
Non-cash interest	$	8			$	6			$	24			$	6
Non-cash interest	$	8			$	6			$	24			$	6


-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 be 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	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Asset Retirement Obligations	'
	Asset Retirement Obligations
	A reconciliation of the Company’s asset retirement obligations for the nine months ended September 30, 2013 is as follows (in thousands):



	As of December 31, 2012	$	47,616

	Liabilities incurred	2,095

	Liabilities settled	(824		)
	Disposition of properties	(387		)
	Accretion expense	2,604

	Revisions to estimate	1,218

	As of September 30, 2013	$	52,322

	Less: liabilities associated with properties held for sale	13,082

	Less: current asset retirement obligations	948

	Long-term asset retirement obligations	$	38,292

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 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 September 30, 2013
		Level 1		Level 2		Level 3		Total
		(in thousands)
	Assets
	Deferred Compensation Plan	$	920	$	—	$	—	$	920

	Cash Equivalents - Money Market Funds	53		—		—		53

	Commodity Derivatives	—		16,881		—		16,881

	Liabilities
	Commodity Derivatives	$	—	$	11,804	$	—	$	11,804





		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 Unaudited 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 10) 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 other current and other long-term assets on the Unaudited 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, which represent Level 1 inputs. The fair values of the Company’s fixed rate 7.625% Senior Notes and 7.0% Senior Notes totaled $800.0 million as of September 30, 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 crude oil, natural gas and NGL forwards and options 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 $390.0 million and zero as of September 30, 2013 and December 31, 2012, respectively, approximates its fair value due to its floating rate structure. The Convertible Notes fair value of $25.2 million and $25.3 million as of September 30, 2013 and December 31, 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 $88.1 million and $97.7 million as of September 30, 2013 and December 31, 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 September 30, 2013 and December 31, 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 nine months ended September 30, 2013 the Company recorded impairment charges of $216.6 million on proved and unproved oil and gas properties. Included in the total impairment charge of $216.6 million was $201.3 million of impairment charges related to assets held for sale at September 30, 2013 for both proved and unproved oil and gas properties for which the Company utilized third party purchase offers as the basis for determining fair value. The inputs used to determine such fair value for other non-recurring impairment testes are primarily based upon internally developed cash flow models as well as available external market data and would generally be classified within Level 3.
	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	9 Months Ended
	Sep. 30, 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 may at times 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 Unaudited 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 Unaudited Consolidated Balance Sheets as of the dates indicated.


		As of September 30, 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	$	12,217			$	(8,711	)	(1)	$	3,506

	Deferred financing costs and other noncurrent assets	4,664				(822		)	(1)	3,842			(2)

	Total derivative assets	$	16,881			$	(9,533	)		$	7,348

		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	$	(10,982	)		$	8,711		(3)	$	(2,271	)

	Derivatives and other noncurrent liabilities	(822		)		822			(3)	—

	Total derivative liabilities	$	(11,804	)		$	9,533			$	(2,271	)


		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 Unaudited Consolidated Balance Sheets.

	-2	As of September 30, 2013 and December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $20.2 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 Unaudited Consolidated Balance Sheets.

	-4	As of December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $4.1 million of other noncurrent liabilities.
	The following table summarizes the cash flow hedge gains, net of tax, and their locations on the Unaudited Consolidated Balance Sheets and Unaudited Consolidated Statements of Operations as of the periods indicated:



		Derivatives Qualifying as		Three Months Ended September 30,								Nine Months Ended September 30,
Cash Flow Hedges		2013				2012				2013				2012
				(in thousands)
Amount of Gain Reclassified from AOCI into Income (net of tax) (1) (2)	Commodity Hedges		$	1,186			$	12,739			$	3,688			$	41,644



-1	Gains reclassified from AOCI into income are included in the oil, gas and NGL production revenues in the Unaudited Consolidated Statements of Operations.

-2	Presented net of income tax expense of $0.7 million and $7.7 million for the three months ended September 30, 2013 and 2012, respectively, and $2.2 million and $25.0 million for the nine months ended September 30, 2013 and 2012, respectively.

As of September 30, 2013, the Company had financial instruments in place to hedge the following volumes for the periods indicated:


	October –December			For the year			For the year
	2013			2014			2015
Oil (Bbls)	806,300			2,972,200			401,200

Natural Gas (MMbtu)	11,355,000			30,415,000			3,650,000

Natural Gas Liquids (Bbls)	98,214			35,714			—

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:


	Three Months Ended September 30,								Nine Months Ended September 30,
	2013				2012				2013				2012
	(in thousands)
Commodity derivative settlements on derivatives designated as cash flow hedges (1)	$	1,899			$	20,391			$	5,902			$	66,654

Total commodity derivative gain (loss) (2)	(25,595		)		(38,340		)		(18,607		)		53,431



-1	Included in oil, gas and NGL production revenues in the Unaudited Consolidated Statements of Operations.

-2	Included in commodity derivative gain (loss) in the Unaudited 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 11 different counterparties as of September 30, 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. One counterparty that was a lender in the Amended Credit Facility withdrew from the facility when the Company amended the facility in October 2011. The Company will continue to monitor the creditworthiness of this counterparty during the remaining duration of the derivatives that were entered into while that counterparty was a lender 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	9 Months Ended
Income Taxes	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The Company accounts for uncertainty in income taxes for tax positions taken or expected to be taken in a tax return in accordance with the FASB’s rules on income taxes. 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 technical merits. During the three and nine months ended September 30, 2013, there was no change to the Company’s liability for uncertain tax positions.
	The Company’s policy is to classify accrued penalties and interest related to unrecognized tax benefits in the Company’s income tax provision. The Company did not record any accrued interest or penalties associated with unrecognized tax benefits during the three and nine months ended September 30, 2013.
	Income tax benefit for the three and nine months ended September 30, 2013 and 2012 differs from the amounts that would be provided by applying the U.S. federal income tax rate to income before income taxes principally due to the effect of state income taxes, stock-based compensation and other operating expenses not deductible for income tax purposes.

Equity_Incentive_Compensation_

Equity Incentive Compensation Plans and Other Employee Benefits	9 Months Ended
	Sep. 30, 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 benefits 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:



		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013				2012
		(in thousands)
	Common stock options	$	681		$	1,626		$	3,898			$	5,299

	Nonvested equity common stock	1,562			1,711			5,550				5,485

	Nonvested equity common stock units	277			371			989				371

	Nonvested performance-based equity	712			372			1,410				1,175

	Total	$	3,232		$	4,080		$	11,847			$	12,330


	Unrecognized compensation cost as of September 30, 2013 was $22.2 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 2.4 years.
	Stock Options and Nonvested Equity Shares. The following tables present the equity awards granted pursuant to the Company’s various stock compensation plans:


		Three Months Ended September 30, 2013					Three Months Ended September 30, 2012
		Number		Weighted Average			Number			Weighted Average
		of Options		Price Per Share			of Options			Price Per Share
	Options to purchase shares of common stock	—		$	—		26,602			$	20.23

		Three Months Ended September 30, 2013					Three Months Ended September 30, 2012
		Number of		Weighted Average			Number of			Weighted Average
		Shares		Grant Date Fair			Shares			Grant Date Fair
				Value Per Share						Value Per Share
	Nonvested equity common stock	57,792		$	22.36		31,664			$	21.64

	Nonvested equity common stock units	2,210		$	25.11		52,917			$	18.94

	Nonvested performance-based equity shares	154,314		$	20.86		3,400			$	23.48

	Total shares granted	214,316					87,981



		Nine Months Ended September 30, 2013					Nine Months Ended September 30, 2012
		Number		Weighted Average			Number			Weighted Average
		of Options		Price Per Share			of Options			Price Per Share
	Options to purchase shares of common stock	—		$	—		582,284			$	27.16

		Nine Months Ended September 30, 2013					Nine Months Ended September 30, 2012
		Number of		Weighted Average			Number of			Weighted Average
		Shares		Grant Date Fair			Shares			Grant Date Fair
				Value Per Share						Value Per Share
	Nonvested equity common stock	615,052		$	17.8		260,778			$	26.06

	Nonvested equity common stock units	54,429		$	22.17		52,917			$	18.94

	Nonvested performance-based equity shares	442,300		$	18.08		179,987			$	26.26

	Total shares granted	1,111,781					493,682


	Performance Share Programs. 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, the Compensation Committee will meet 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, and the Company recorded zero and $0.2 million of non-cash stock-based compensation expense related to these awards for the three and nine months ended September 30, 2012. Based upon the Company’s performance in 2012, none of the 2010 Program performance shares vested in February 2013. The Company recorded $0.1 million and $0.3 million of non-cash stock-based compensation expense for the nine months ended September 30, 2013 and 2012, respectively.
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 Company recorded $0.1 million and $0.3 million of non-cash stock-based compensation expense related to these awards for the three months ended September 30, 2013 and 2012, respectively, and $0.1 million and $0.7 million of non-cash stock-based compensation expense for the nine months ended September 30, 2013 and 2012, respectively.
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 ending December 31, 2013, the performance goals consist of the Company’s total shareholder return (“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 $0.1 million and 0.3 million of non-cash stock-based compensation expense related to these awards during the three and nine months ended September 30, 2013, respectively.

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 TSR ranking relative to a defined peer group’s individual TSRs. 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. The Company recorded $0.03 million and $0.08 million of non-cash stock-based compensation expense related to these awards for the three and nine months ended September 30, 2013, respectively.
In February 2013, the Compensation Committee approved a new performance share program (the “2013 Program”) pursuant to the 2012 Equity Incentive Plan (“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 TSR ranking relative to a defined peer group’s individual TSR (“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 100,434 and 388,420 shares were granted under this program during the three and nine months ended September 30, 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 $0.4 million and $0.8 million of non-cash stock-based compensation expense related to these awards for the three and nine months ended September 30, 2013, 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 three and nine months ended September 30, 2013 and 2012 is presented below:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013				2012
Director fees (shares)	2,210			3,732			14,116				6,907

Stock-based compensation (in thousands)	$	56		$	92		$	297			$	167

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 $0.4 million for the three months ended September 30, 2013 and 2012, and $1.6 million for the nine months ended September 30, 2013 and 2012.

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 deferred compensation liability was $0.9 million and $1.0 million as of September 30, 2013 and December 31, 2012, respectively, of which $0.5 million and $0.3 million were classified as current as of September 30, 2013 and December 31, 2012, respectively.
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.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 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 September 30, 2013
		(in thousands)
	2013	$	3,034

	2014	12,139

	2015	12,139

	2016	12,139

	2017	12,139

	Thereafter	32,368

	Total (1)	$	83,958



	-1	The balance shown in this table includes the approximately 51% of the Lease Financing Obligation that the purchaser will assume upon closing of the West Tavaputs Sale in December 2013. See Note 13.
	Transportation Demand and Firm Processing Charges. The Company has entered into contracts that provide firm transportation capacity on pipeline systems and firm processing charges. The remaining terms on these contracts range from 2 to 10 years and require the Company to pay transportation demand and processing charges regardless of the amount of pipeline capacity utilized by the Company. The Company paid $9.5 million and $27.8 million of transportation demand charges for the three and nine months ended September 30, 2013, respectively. The Company paid $1.4 million and $3.5 million of firm processing charges for the three and nine months ended September 30, 2013, respectively. All transportation costs, including demand charges and processing charges, are included in gathering, transportation and processing expense in the Unaudited Consolidated Statements of Operations. The Company paid $11.3 million and $33.7 million of transportation demand charges for the three and nine months ended September 30, 2012, respectively. The Company paid $1.6 million and $4.6 million of firm processing charges for the three and nine months ended September 30, 2012, respectively.
	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 September 30, 2013
		(in thousands)
	2013	$	14,450

	2014	57,929

	2015	58,065

	2016	56,464

	2017	51,824

	Thereafter	147,984

	Total (1)	$	386,716



	-1	The balance shown in this table includes $137.7 million of transportation demand and firm processing charges that the purchaser will assume upon closing of the West Tavaputs Sale in December 2013. See Note 13.
	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. 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 $0.5 million and $1.5 million for both the three and nine months ended September 30, 2013 and 2012, 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 September 30, 2013
		(in thousands)
	2013	$	1,069

	2014	4,561

	2015	3,099

	2016	2,593

	2017	2,517

	Thereafter	3,158

Total	$	16,997

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 unaudited consolidated balance sheet, cash flows or statements of operations.

Guarantor_Subsidiaries

Guarantor Subsidiaries	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]	'
Guarantor Subsidiaries	'
	Guarantor Subsidiaries
	In addition to the Amended Credit Facility, 7.625% Senior Notes, 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 Company’s 100% owned subsidiaries (“Guarantor Subsidiaries”). Presented below are the Company’s unaudited 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 unaudited condensed consolidating financial statements have been prepared from the Company’s financial information on the same basis of accounting as the Unaudited 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 September 30, 2013
		Parent				Guarantor				Intercompany			Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Assets:
	Current assets	$	165,436			$	3,615			$	—		$	169,051

	Property and equipment, net	2,410,495				122,650				—			2,533,145

	Intercompany receivable (payable)	156,414				(156,414		)		—			—

	Investment in subsidiaries	(35,826		)		—				35,826			—

	Noncurrent assets	24,065				—				—			24,065

	Total assets	$	2,720,584			$	(30,149	)		$	35,826		$	2,726,261

	Liabilities and Stockholders’ Equity:
	Current liabilities	$	205,331			$	906			$	—		$	206,237

	Long-term debt	1,255,243				—				—			1,255,243

	Deferred income taxes	153,847				2,187				—			156,034

	Other noncurrent liabilities	99,165				2,584				—			101,749

	Stockholders’ equity	1,006,998				(35,826		)		35,826			1,006,998

	Total liabilities and stockholders’ equity	$	2,720,584			$	(30,149	)		$	35,826		$	2,726,261




		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


	Three Months Ended September 30, 2013
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Operating and other revenues	$	139,286			$	9,269			$	—		$	148,555

Operating expenses	(329,791		)		(4,432		)		—			(334,223		)

General and administrative	(14,402		)		—				—			(14,402		)

Interest income and other income (expense)	(67,081		)		—				—			(67,081		)

Income (loss) before income taxes and equity in earnings of subsidiaries	(271,988		)		4,837				—			(267,151		)

Benefit from income taxes	100,495				—				—			100,495

Equity in earnings of subsidiaries	4,837				—				(4,837		)	—

Net income (loss)	$	(166,656	)		$	4,837			$	(4,837	)	$	(166,656	)




	Nine Months Ended September 30, 2013
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Operating and other revenues	$	405,057			$	24,074			$	—		$	429,131

Operating expenses	(556,070		)		(12,367		)		—			(568,437		)

General and administrative	(48,257		)		—				—			(48,257		)

Interest income and other income (expense)	(109,290		)		—				—			(109,290		)

Income (loss) before income taxes and equity in earnings of subsidiaries	(308,560		)		11,707				—			(296,853		)

Benefit from income taxes	111,319				—				—			111,319

Equity in earnings of subsidiaries	11,707				—				(11,707		)	—

Net income (loss)	$	(185,534	)		$	11,707			$	(11,707	)	$	(185,534	)




	Three Months Ended September 30, 2012
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Operating and other revenues	$	172,054			$	8,812			$	—		$	180,866

Operating expenses	(179,917		)		(5,399		)		—			(185,316		)

General and administrative	(17,965		)		—				—			(17,965		)

Interest and other income (expense)	(62,814		)		—				—			(62,814		)

Income (loss) before income taxes and equity in earnings of subsidiaries	(88,642		)		3,413				—			(85,229		)

Benefit from income taxes	32,603				—				—			32,603

Equity in earnings of subsidiaries	3,413				—				(3,413		)	—

Net income (loss)	$	(52,626	)		$	3,413			$	(3,413	)	$	(52,626	)



	Nine Months Ended September 30, 2012
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Operating and other revenues	$	502,175			$	18,219			$	—		$	520,394

Operating expenses	(461,243		)		(14,219		)		—			(475,462		)

General and administrative	(51,441		)		—				—			(51,441		)

Interest and other income (expense)	(14,869		)		—				—			(14,869		)

Income (loss) before income taxes and equity in earnings of subsidiaries	(25,378		)		4,000				—			(21,378		)

Benefit from income taxes	7,943				—				—			7,943

Equity in earnings of subsidiaries	4,000				—				(4,000		)	—

Net income (loss)	$	(13,435	)		$	4,000			$	(4,000	)	$	(13,435	)

Condensed Consolidating Statements of Comprehensive Income (Loss)



	Three Months Ended September 30, 2013
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Net income (loss)	$	(166,656	)		$	4,837			$	(4,837	)	$	(166,656	)

Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(1,186		)		—				—			(1,186		)

Other comprehensive loss	(1,186		)		—				—			(1,186		)

Comprehensive income (loss)	$	(167,842	)		$	4,837			$	(4,837	)	$	(167,842	)


	Nine Months Ended September 30, 2013
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Net income (loss)	$	(185,534	)		$	11,707			$	(11,707	)	$	(185,534	)

Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(3,688		)		—				—			(3,688		)

Other comprehensive loss	(3,688		)		—				—			(3,688		)

Comprehensive income (loss)	$	(189,222	)		$	11,707			$	(11,707	)	$	(189,222	)



	Three Months Ended September 30, 2012
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Net income (loss)	$	(52,626	)		$	3,413			$	(3,413	)	$	(52,626	)

Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(12,739		)		—				—			(12,739		)

Other comprehensive loss	(12,739		)		—				—			(12,739		)

Comprehensive income (loss)	$	(65,365	)		$	3,413			$	(3,413	)	$	(65,365	)


	Nine Months Ended September 30, 2012
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Net income (loss)	$	(13,435	)		$	4,000			$	(4,000	)	$	(13,435	)

Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(41,644		)		—				—			(41,644		)

Other comprehensive loss	(41,644		)		—				—			(41,644		)

Comprehensive income (loss)	$	(55,079	)		$	4,000			$	(4,000	)	$	(55,079	)


Condensed Consolidating Statements of Cash Flows



	Nine Months Ended September 30, 2013
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Cash flows from operating activities	$	179,003			$	17,299			$	—		$	196,302

Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(303,366		)		(32,231		)		—			(335,597		)

Additions to furniture, fixtures and other	(1,506		)		—				—			(1,506		)

Proceeds from sale of properties and other investing activities	784				—				—			784

Cash flows from financing activities:
Proceeds from debt	390,000				—				—			390,000

Principal and redemption premium payments on debt	(269,125		)		—				—			(269,125		)

Intercompany transfers	(14,932		)		14,932				—			—

Other financing activities	227				—				—			227

Change in cash and cash equivalents	(18,915		)		—				—			(18,915		)

Beginning cash and cash equivalents	79,395				50				—			79,445

Ending cash and cash equivalents	$	60,480			$	50			$	—		$	60,530




	Nine Months Ended September 30, 2012
	Parent				Guarantor				Intercompany			Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Cash flows from operating activities	$	284,188			$	6,415			$	—		$	290,603

Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(727,818		)		(23,727		)		—			(751,545		)

Additions to furniture, fixtures and other	(5,519		)		—				—			(5,519		)

Proceeds from sale of properties and other investing activities	91				—				—			91

Cash flows from financing activities:
Proceeds from debt	785,826				—				—			785,826

Principal and redemption premium payments on debt	(343,163		)		—				—			(343,163		)

Intercompany transfers	(17,312		)		17,312				—			—

Other financing activities	(9,691		)		—				—			(9,691		)

Change in cash and cash equivalents	(33,398		)		—				—			(33,398		)

Beginning cash and cash equivalents	57,281				50				—			57,331

Ending cash and cash equivalents	$	23,883			$	50			$	—		$	23,933

Subsequent_Events

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2013
Subsequent Events [Abstract]	'
Subsequent Events	'
	Subsequent Events
	On October 22, 2013, the Company entered into a purchase and sale agreement for the sale of the Company’s West Tavaputs natural gas property located in the Uinta Basin, Utah. Total consideration, prior to customary closing adjustments, for the West Tavaputs Sale is $371.5 million and includes approximately $46.0 million for the purchaser’s assumption of the Lease Financing Obligation. The transaction is expected to close by the end of 2013. The Company recognized impairment expense of $201.3 million related to these assets in the three months ended September 30, 2013.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation. The accompanying unaudited 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. In the opinion of management, the accompanying financial statements include all adjustments (consisting of normal recurring accruals and adjustments) necessary to present fairly, in all material respects, the Company’s interim results. However, operating results for the periods presented are not necessarily indicative of the results that may be expected for the full year.
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 undeveloped properties, valuing deferred tax assets and estimating fair values of derivative instruments and stock-based payment awards.
Accounts Receivable	'
	Accounts Receivable. Accounts receivable is comprised of the following:



		As of September 30, 2013			As of December 31, 2012
		(in thousands)
	Accrued oil, gas and NGL sales	$	68,013		$	69,482

	Due from joint interest owners	28,489			36,300

	Other	3,058			6,554

	Allowance for doubtful accounts	(23		)	(325		)
	Total accounts receivable	$	99,537		$	112,011

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 Unaudited 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 Unaudited 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 September 30, 2013			As of December 31, 2012
		(in thousands)
	Proved properties	$	422,083		$	387,242

	Wells and related equipment and facilities	2,080,178			2,625,891

	Support equipment and facilities	163,242			304,914

	Materials and supplies	10,193			13,220

	Total proved oil and gas properties	$	2,675,696		$	3,331,267

	Unproved properties	307,557			384,486

	Wells and facilities in progress	54,829			72,721

	Total unproved oil and gas properties, excluded from amortization	$	362,386		$	457,207

	Oil and gas properties held for sale, net (1)	378,449			—

	Accumulated depreciation, depletion, amortization and impairment	(907,222		)	(1,203,495		)
	Total oil and gas properties, net	$	2,509,309		$	2,584,979


	-1	The oil and gas properties held for sale balance shown in this table is different from the balance on the Unaudited Consolidated Balance Sheet because it does not include $4.1 million of furniture, equipment and other, net.
	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. As of September 30, 2013 and December 31, 2012, there were no exploratory well costs that had been capitalized for a period greater than one year since the completion of drilling.
	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 Company has no guarantee that the undiscounted future cash flows analysis of its proved property represents the applicable market value. 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 Unaudited Consolidated Statements of Operations, as follows:



		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands)
	Non-cash impairment of proved oil and gas properties (1)	$	198,787		$	—		$	198,787		$	—

	Non-cash impairment of unproved oil and gas properties (2) (3)	17,777			18,772			17,777			37,109

	Dry hole costs	(36		)	15,658			928			15,891

	Abandonment expense	2,835			4,110			10,154			7,179

	Total non-cash impairment, dry hole costs and abandonment expense	$	219,363		$	38,540		$	227,646		$	60,179



	-1	Non-cash impairment of proved oil and gas properties for the three and nine months ended September 30, 2013 related to assets classified as held for sale at September 30, 2013. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.

	-2	Non-cash impairment of unproved oil and gas properties for the three and nine months ended September 30, 2013 was comprised of $15.3 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 unproved properties held for sale at September 30, 2013.

	-3	Non-cash impairment of unproved oil and gas properties for the three months ended September 30, 2012 of $18.8 million 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. The additional $18.3 million unproved oil and gas properties impairment expense for the nine months ended September 30, 2012 also related to unproved oil and gas properties within other exploration and development projects primarily as a result of unfavorable market conditions or no future plans to evaluate the remaining acreage.
	The provision for DD&A of oil and gas properties is calculated on a field-by-field basis using the unit-of-production method. Oil and NGLs are converted to natural gas equivalents, Mcfe, at the standard rate of one barrel to six Mcfe. 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. Accounts payable and accrued liabilities are comprised of the following:


		As of September 30, 2013			As of December 31, 2012
		(in thousands)
	Accrued drilling, completion and facility costs	$	63,618		$	42,094

	Accrued lease operating, gathering, transportation and processing expenses	19,481			16,862

	Accrued general and administrative expenses	8,542			13,054

	Trade payables and other	31,768			53,007

	Total accounts payable and accrued liabilities	$	123,409		$	125,017

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 crude 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 September 30, 2013 and December 31, 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 Unaudited 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 Per Share	'
	Earnings/Loss Per Share. Basic net loss per common share is calculated by dividing net loss attributable to common stock by the weighted average number of common shares outstanding during each period. Diluted net loss per common share is calculated by dividing net 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 three and nine months ended September 30, 2013 and 2012.

	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 September 30, 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 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. The Convertible Notes have not been dilutive since their issuance in March 2008 and, therefore, did not impact the diluted net loss per common share calculation for the three and nine months ended September 30, 2013 and 2012. The diluted net loss per common share excludes the anti-dilutive effect of 2,450,539 and 3,799,612 shares of stock options and nonvested equity shares of common stock for the three months ended September 30, 2013 and 2012, respectively, and 2,731,578 and 3,829,825 shares of stock options and nonvested equity shares of common stock for the nine months ended September 30, 2013 and 2012, respectively.
	The following table sets forth the calculation of basic and diluted loss per share:



		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands, except per share amounts)
	Net loss	$	(166,656	)	$	(52,626	)	$	(185,534	)	$	(13,435	)
	Basic weighted-average common shares outstanding in period	47,535			47,230			47,453			47,173

	Add dilutive effects of stock options and nonvested equity shares of common stock	—			—			—			—

	Diluted weighted-average common shares outstanding in period	47,535			47,230			47,453			47,173

	Basic net loss per common share	$	(3.51	)	$	(1.11	)	$	(3.91	)	$	(0.28	)
	Diluted net loss per common share	$	(3.51	)	$	(1.11	)	$	(3.91	)	$	(0.28	)
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)	9 Months Ended
Summary of Significant Accounting Policies (Tables)	Sep. 30, 2013
Accounting Policies [Abstract]	'
Summary of Accounts Receivable	'
	Accounts receivable is comprised of the following:



		As of September 30, 2013			As of December 31, 2012
		(in thousands)
	Accrued oil, gas and NGL sales	$	68,013		$	69,482
	Accrued oil, gas and NGL sales	$	68,013		$	69,482
	Due from joint interest owners	28,489			36,300
	Due from joint interest owners	28,489			36,300
	Other	3,058			6,554
	Other	3,058			6,554
	Allowance for doubtful accounts	(23		)	(325		)
	Total accounts receivable	$	99,537		$	112,011
	Total accounts receivable	$	99,537		$	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 September 30, 2013			As of December 31, 2012
		(in thousands)
	Proved properties	$	422,083		$	387,242
	Proved properties	$	422,083		$	387,242
	Wells and related equipment and facilities	2,080,178			2,625,891
	Wells and related equipment and facilities	2,080,178			2,625,891
	Support equipment and facilities	163,242			304,914
	Support equipment and facilities	163,242			304,914
	Materials and supplies	10,193			13,220
	Materials and supplies	10,193			13,220
	Total proved oil and gas properties	$	2,675,696		$	3,331,267
	Total proved oil and gas properties	$	2,675,696		$	3,331,267
	Unproved properties	307,557			384,486
	Unproved properties	307,557			384,486
	Wells and facilities in progress	54,829			72,721
	Wells and facilities in progress	54,829			72,721
	Total unproved oil and gas properties, excluded from amortization	$	362,386		$	457,207
		$	362,386		$	457,207
	Oil and gas properties held for sale, net (1)	378,449			—
	Oil and gas properties held for sale, net (1)	378,449			—
	Accumulated depreciation, depletion, amortization and impairment	(907,222		)	(1,203,495		)
	Total oil and gas properties, net	$	2,509,309		$	2,584,979
	Total oil and gas properties, net	$	2,509,309		$	2,584,979

	-1	The oil and gas properties held for sale balance shown in this table is different from the balance on the Unaudited Consolidated Balance Sheet because it does not include $4.1 million of furniture, equipment and other, net.
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 Unaudited Consolidated Statements of Operations, as follows:



		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands)
	Non-cash impairment of proved oil and gas properties (1)	$	198,787		$	—		$	198,787		$	—
	Non-cash impairment of proved oil and gas properties (1)	$	198,787		$	—		$	198,787		$	—
	Non-cash impairment of unproved oil and gas properties (2) (3)	17,777			18,772			17,777			37,109
		17,777			18,772			17,777			37,109
	Dry hole costs	(36		)	15,658			928			15,891
	Dry hole costs	(36		)	15,658			928			15,891
	Abandonment expense	2,835			4,110			10,154			7,179
	Abandonment expense	2,835			4,110			10,154			7,179
	Total non-cash impairment, dry hole costs and abandonment expense	$	219,363		$	38,540		$	227,646		$	60,179
		$	219,363		$	38,540		$	227,646		$	60,179


	-1	Non-cash impairment of proved oil and gas properties for the three and nine months ended September 30, 2013 related to assets classified as held for sale at September 30, 2013. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.

	-2	Non-cash impairment of unproved oil and gas properties for the three and nine months ended September 30, 2013 was comprised of $15.3 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 unproved properties held for sale at September 30, 2013.

	-3	Non-cash impairment of unproved oil and gas properties for the three months ended September 30, 2012 of $18.8 million 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. The additional $18.3 million unproved oil and gas properties impairment expense for the nine months ended September 30, 2012 also related to unproved oil and gas properties within other exploration and development projects primarily as a result of unfavorable market conditions or no future plans to evaluate the remaining acreage.
Accounts Payable and Accrued Liabilities	'
	Accounts payable and accrued liabilities are comprised of the following:


		As of September 30, 2013			As of December 31, 2012
		(in thousands)
	Accrued drilling, completion and facility costs	$	63,618		$	42,094
	Accrued drilling, completion and facility costs	$	63,618		$	42,094
	Accrued lease operating, gathering, transportation and processing expenses	19,481			16,862
		19,481			16,862
	Accrued general and administrative expenses	8,542			13,054
	Accrued general and administrative expenses	8,542			13,054
	Trade payables and other	31,768			53,007
	Trade payables and other	31,768			53,007
	Total accounts payable and accrued liabilities	$	123,409		$	125,017
	Total accounts payable and accrued liabilities	$	123,409		$	125,017
Calculation of Basic and Diluted Earnings Per Share	'
	The following table sets forth the calculation of basic and diluted loss per share:



		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands, except per share amounts)
	Net loss	$	(166,656	)	$	(52,626	)	$	(185,534	)	$	(13,435	)
	Basic weighted-average common shares outstanding in period	47,535			47,230			47,453			47,173
	Basic weighted-average common shares outstanding in period	47,535			47,230			47,453			47,173
	Add dilutive effects of stock options and nonvested equity shares of common stock	—			—			—			—
		—			—			—			—
	Diluted weighted-average common shares outstanding in period	47,535			47,230			47,453			47,173
		47,535			47,230			47,453			47,173
	Basic net loss per common share	$	(3.51	)	$	(1.11	)	$	(3.91	)	$	(0.28	)
	Diluted net loss per common share	$	(3.51	)	$	(1.11	)	$	(3.91	)	$	(0.28	)

Supplemental_Disclosures_of_Ca1

Supplemental Disclosures of Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information	'
	Supplemental cash flow information is as follows:


		Nine Months Ended September 30,
		2013			2012
		(in thousands)
	Cash paid for interest, net of amount capitalized	$	61,796		$	49,040

	Cash paid for income taxes	1,861			11

	Supplemental disclosures of non-cash investing and financing activities:
	Current liabilities	75,265			75,092

	Net increase in asset retirement obligations	2,924			280

	Retirement of treasury stock	(1,415		)	(2,430		)

Divestitures_and_Assets_Held_f1

Divestitures and Assets Held for Sale Asset Held for Sale (Tables) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Long Lived Assets Held-for-sale [Line Items]	'
Long Lived Assets Held-for-sale, Impairment Charge	$201.30
Disclosure of Long Lived Assets Held-for-sale [Table Text Block]	'
	See the table below for detail of the assets held for sale included on the Unaudited Consolidated Balance Sheet:


		As of September 30, 2013
		(in thousands)
	Assets
	Proved properties	$	1,070,400

	Unproved properties	12,469

	Furniture, equipment and other	4,205

	Accumulated depreciation, depletion, amortization and impairment	(704,520		)
	Total assets held for sale	$	382,554


	Liabilities
	Asset retirement obligation held for sale	13,082

	Lease financing obligation held for sale	46,363

	Total liabilities held for sale	$	59,445


	Net assets	$	323,109

LongTerm_Debt_Tables

Long-Term Debt (Tables)	9 Months Ended
Long-Term Debt (Tables)	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Outstanding Debt	'
	The Company’s outstanding debt is summarized below:



			As of September 30, 2013									As of December 31, 2012
		Maturity Date	Principal			Unamortized			Carrying			Principal		Unamortized			Carrying
		Maturity Date	Principal			Discount			Amount			Principal		Discount			Amount
			(in thousands)
	Amended Credit Facility (1)	October 31, 2016	$	390,000		$	—		$	390,000		$	—	$	—		$	—
	Amended Credit Facility (1)	October 31, 2016	$	390,000		$	—		$	390,000		$	—	$	—		$	—
	9.875% Senior Notes (2)	July 15, 2016	—			—			—			250,000		(7,209		)	242,791
	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
	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
	7.625% 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
	7.0% Senior Notes (6)	October 15, 2022	400,000			—			400,000			400,000		—			400,000
	Lease Financing Obligation (7)	August 10, 2020	44,453			—			44,453			97,596		—			97,596
	Lease Financing Obligation (7)	August 10, 2020	44,453			—			44,453			97,596		—			97,596
	Total Debt		$	1,259,797		$	—		$	1,259,797		$	1,172,940	$	(7,209	)	$	1,165,731
	Total Debt		$	1,259,797		$	—		$	1,259,797		$	1,172,940	$	(7,209	)	$	1,165,731
	Less: Current Portion of Long-Term Debt		4,554			—			4,554			9,077		—			9,077
	Less: Current Portion of Long-Term Debt		4,554			—			4,554			9,077		—			9,077
	Total Long-Term Debt (8)		$	1,255,243		$	—		$	1,255,243		$	1,163,863	$	(7,209	)	$	1,156,654
	Total Long-Term Debt (8)		$	1,255,243		$	—		$	1,255,243		$	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.

	-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 $25.2 million and $25.3 million as of September 30, 2013 and December 31, 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 $410.0 million and $435.0 million as of September 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

	-6	The aggregate estimated fair value of the 7.0% Senior Notes was approximately $390.0 million and $413.8 million as of September 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

	-7	The aggregate estimated fair value of the full Lease Financing Obligation was approximately $88.1 million as of September 30, 2013, 51% of which is held for sale at September 30, 2013, and $97.7 million as of December 31, 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.

	-8	The total long-term debt balance excludes $46.4 million related to the Lease Financing Obligation that is included in liabilities associated with assets held for sale in the Unaudited Consolidated Balance Sheet. See Note 4 for additional information.
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:



		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands)
	Amended Credit Facility (1)
	Cash interest	$	2,296		$	1,453		$	4,211		$	3,707
	Cash interest	$	2,296		$	1,453		$	4,211		$	3,707
	Non-cash interest	$	585		$	586		$	1,756		$	1,757
	Non-cash interest	$	585		$	586		$	1,756		$	1,757
	9.875% Senior Notes (2)
	Cash interest	$	1,029		$	6,172		$	13,373		$	18,516
	Cash interest	$	1,029		$	6,172		$	13,373		$	18,516
	Non-cash interest	$	—		$	657		$	1,361		$	1,911
	Non-cash interest	$	—		$	657		$	1,361		$	1,911
	Convertible Notes (3)
	Cash interest	$	310		$	317		$	943		$	2,585
	Cash interest	$	310		$	317		$	943		$	2,585
	Non-cash interest	$	1		$	1		$	4		$	1,770
	Non-cash interest	$	1		$	1		$	4		$	1,770
	7.625% Senior Notes (4)
	Cash interest	$	7,625		$	7,625		$	22,875		$	22,875
	Cash interest	$	7,625		$	7,625		$	22,875		$	22,875
	Non-cash interest	$	272		$	262		$	798		$	803
	Non-cash interest	$	272		$	262		$	798		$	803
	7.0% Senior Notes (5)
	Cash interest	$	7,000		$	7,000		$	21,000		$	15,397
	Cash interest	$	7,000		$	7,000		$	21,000		$	15,397
	Non-cash interest	$	203		$	197		$	592		$	464
	Non-cash interest	$	203		$	197		$	592		$	464
	Lease Financing Obligation (6)
	Cash interest	$	750		$	548		$	2,305		$	548
	Cash interest	$	750		$	548		$	2,305		$	548
	Non-cash interest	$	8		$	6		$	24		$	6
	Non-cash interest	$	8		$	6		$	24		$	6


	-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 be 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)	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Schedule of Asset Retirement Obligations	'
	A reconciliation of the Company’s asset retirement obligations for the nine months ended September 30, 2013 is as follows (in thousands):



	As of December 31, 2012	$	47,616

	Liabilities incurred	2,095

	Liabilities settled	(824		)
	Disposition of properties	(387		)
	Accretion expense	2,604

	Revisions to estimate	1,218

	As of September 30, 2013	$	52,322

	Less: liabilities associated with properties held for sale	13,082

	Less: current asset retirement obligations	948

	Long-term asset retirement obligations	$	38,292

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
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 September 30, 2013
		Level 1		Level 2		Level 3		Total
		(in thousands)
	Assets
	Deferred Compensation Plan	$	920	$	—	$	—	$	920

	Cash Equivalents - Money Market Funds	53		—		—		53

	Commodity Derivatives	—		16,881		—		16,881

	Liabilities
	Commodity Derivatives	$	—	$	11,804	$	—	$	11,804





		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)	9 Months Ended
	Sep. 30, 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 Unaudited Consolidated Balance Sheets as of the dates indicated.


		As of September 30, 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	$	12,217			$	(8,711	)	(1)	$	3,506

	Deferred financing costs and other noncurrent assets	4,664				(822		)	(1)	3,842			(2)

	Total derivative assets	$	16,881			$	(9,533	)		$	7,348

		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	$	(10,982	)		$	8,711		(3)	$	(2,271	)

	Derivatives and other noncurrent liabilities	(822		)		822			(3)	—

	Total derivative liabilities	$	(11,804	)		$	9,533			$	(2,271	)


		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 Unaudited Consolidated Balance Sheets.

	-2	As of September 30, 2013 and December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $20.2 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 Unaudited Consolidated Balance Sheets.

	-4	As of December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $4.1 million of other noncurrent liabilities.
Cash Flow Hedge Gains and Losses	'
	The following table summarizes the cash flow hedge gains, net of tax, and their locations on the Unaudited Consolidated Balance Sheets and Unaudited Consolidated Statements of Operations as of the periods indicated:



		Derivatives Qualifying as		Three Months Ended September 30,								Nine Months Ended September 30,
		Cash Flow Hedges		2013				2012				2013				2012
				(in thousands)
	Amount of Gain Reclassified from AOCI into Income (net of tax) (1) (2)	Commodity Hedges		$	1,186			$	12,739			$	3,688			$	41,644



	-1	Gains reclassified from AOCI into income are included in the oil, gas and NGL production revenues in the Unaudited Consolidated Statements of Operations.

	-2	Presented net of income tax expense of $0.7 million and $7.7 million for the three months ended September 30, 2013 and 2012, respectively, and $2.2 million and $25.0 million for the nine months ended September 30, 2013 and 2012, respectively.
Financial Instruments for Hedging Volumes	'
	As of September 30, 2013, the Company had financial instruments in place to hedge the following volumes for the periods indicated:


		October –December			For the year			For the year
		2013			2014			2015
	Oil (Bbls)	806,300			2,972,200			401,200

	Natural Gas (MMbtu)	11,355,000			30,415,000			3,650,000

	Natural Gas Liquids (Bbls)	98,214			35,714			—

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:


		Three Months Ended September 30,								Nine Months Ended September 30,
		2013				2012				2013				2012
		(in thousands)
	Commodity derivative settlements on derivatives designated as cash flow hedges (1)	$	1,899			$	20,391			$	5,902			$	66,654

	Total commodity derivative gain (loss) (2)	(25,595		)		(38,340		)		(18,607		)		53,431



	-1	Included in oil, gas and NGL production revenues in the Unaudited Consolidated Statements of Operations.

	-2	Included in commodity derivative gain (loss) in the Unaudited Consolidated Statements of Operations.

Equity_Incentive_Compensation_1

Equity Incentive Compensation Plans and Other Employee Benefits (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
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:



		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013				2012
		(in thousands)
	Common stock options	$	681		$	1,626		$	3,898			$	5,299

	Nonvested equity common stock	1,562			1,711			5,550				5,485

	Nonvested equity common stock units	277			371			989				371

	Nonvested performance-based equity	712			372			1,410				1,175

	Total	$	3,232		$	4,080		$	11,847			$	12,330

Stock Options and Nonvested Equity Shares, Equity Awards Granted	'
	The following tables present the equity awards granted pursuant to the Company’s various stock compensation plans:


		Three Months Ended September 30, 2013					Three Months Ended September 30, 2012
		Number		Weighted Average			Number			Weighted Average
		of Options		Price Per Share			of Options			Price Per Share
	Options to purchase shares of common stock	—		$	—		26,602			$	20.23

		Three Months Ended September 30, 2013					Three Months Ended September 30, 2012
		Number of		Weighted Average			Number of			Weighted Average
		Shares		Grant Date Fair			Shares			Grant Date Fair
				Value Per Share						Value Per Share
	Nonvested equity common stock	57,792		$	22.36		31,664			$	21.64

	Nonvested equity common stock units	2,210		$	25.11		52,917			$	18.94

	Nonvested performance-based equity shares	154,314		$	20.86		3,400			$	23.48

	Total shares granted	214,316					87,981



		Nine Months Ended September 30, 2013					Nine Months Ended September 30, 2012
		Number		Weighted Average			Number			Weighted Average
		of Options		Price Per Share			of Options			Price Per Share
	Options to purchase shares of common stock	—		$	—		582,284			$	27.16

		Nine Months Ended September 30, 2013					Nine Months Ended September 30, 2012
		Number of		Weighted Average			Number of			Weighted Average
		Shares		Grant Date Fair			Shares			Grant Date Fair
				Value Per Share						Value Per Share
	Nonvested equity common stock	615,052		$	17.8		260,778			$	26.06

	Nonvested equity common stock units	54,429		$	22.17		52,917			$	18.94

	Nonvested performance-based equity shares	442,300		$	18.08		179,987			$	26.26

	Total shares granted	1,111,781					493,682

Directors Fees	'
	A summary of the Company’s directors’ fees and equity-based compensation for the three and nine months ended September 30, 2013 and 2012 is presented below:


		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013				2012
	Director fees (shares)	2,210			3,732			14,116				6,907

	Stock-based compensation (in thousands)	$	56		$	92		$	297			$	167

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Schedule of Aggregate Undiscounted Minimum Future Lease Payments	'
	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 September 30, 2013
		(in thousands)
	2013	$	3,034

	2014	12,139

	2015	12,139

	2016	12,139

	2017	12,139

	Thereafter	32,368

	Total (1)	$	83,958



	-1	The balance shown in this table includes the approximately 51% of the Lease Financing Obligation that the purchaser will assume upon closing of the West Tavaputs Sale in December 2013. See Note 13
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 September 30, 2013
		(in thousands)
	2013	$	14,450

	2014	57,929

	2015	58,065

	2016	56,464

	2017	51,824

	Thereafter	147,984

	Total (1)	$	386,716



	-1	The balance shown in this table includes $137.7 million of transportation demand and firm processing charges that the purchaser will assume upon closing of the West Tavaputs Sale in December 2013. See Note 13.
Future Minimum Annual Payments Under Drilling, Lease and Other Agreements	'
	Future minimum annual payments under lease and other agreements are as follows:


		As of September 30, 2013
		(in thousands)
	2013	$	1,069

	2014	4,561

	2015	3,099

	2016	2,593

	2017	2,517

	Thereafter	3,158

	Total	$	16,997

Guarantor_Subsidiaries_Tables

Guarantor Subsidiaries (Tables)	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]	'
Schedule of Condensed Consolidating Balance Sheets	'
	Condensed Consolidating Balance Sheets


		As of September 30, 2013
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Assets:
	Current assets	$	165,436			$	3,615			$	—			$	169,051

	Property and equipment, net	2,410,495				122,650				—				2,533,145

	Intercompany receivable (payable)	156,414				(156,414		)		—				—

	Investment in subsidiaries	(35,826		)		—				35,826				—

	Noncurrent assets	24,065				—				—				24,065

	Total assets	$	2,720,584			$	(30,149	)		$	35,826			$	2,726,261

	Liabilities and Stockholders’ Equity:
	Current liabilities	$	205,331			$	906			$	—			$	206,237

	Long-term debt	1,255,243				—				—				1,255,243

	Deferred income taxes	153,847				2,187				—				156,034

	Other noncurrent liabilities	99,165				2,584				—				101,749

	Stockholders’ equity	1,006,998				(35,826		)		35,826				1,006,998

	Total liabilities and stockholders’ equity	$	2,720,584			$	(30,149	)		$	35,826			$	2,726,261




		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


		Three Months Ended September 30, 2013
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Operating and other revenues	$	139,286			$	9,269			$	—			$	148,555

	Operating expenses	(329,791		)		(4,432		)		—				(334,223		)

	General and administrative	(14,402		)		—				—				(14,402		)

	Interest income and other income (expense)	(67,081		)		—				—				(67,081		)

	Income (loss) before income taxes and equity in earnings of subsidiaries	(271,988		)		4,837				—				(267,151		)

	Benefit from income taxes	100,495				—				—				100,495

	Equity in earnings of subsidiaries	4,837				—				(4,837		)		—

	Net income (loss)	$	(166,656	)		$	4,837			$	(4,837	)		$	(166,656	)




		Nine Months Ended September 30, 2013
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Operating and other revenues	$	405,057			$	24,074			$	—			$	429,131

	Operating expenses	(556,070		)		(12,367		)		—				(568,437		)

	General and administrative	(48,257		)		—				—				(48,257		)

	Interest income and other income (expense)	(109,290		)		—				—				(109,290		)

	Income (loss) before income taxes and equity in earnings of subsidiaries	(308,560		)		11,707				—				(296,853		)

	Benefit from income taxes	111,319				—				—				111,319

	Equity in earnings of subsidiaries	11,707				—				(11,707		)		—

	Net income (loss)	$	(185,534	)		$	11,707			$	(11,707	)		$	(185,534	)




		Three Months Ended September 30, 2012
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Operating and other revenues	$	172,054			$	8,812			$	—			$	180,866

	Operating expenses	(179,917		)		(5,399		)		—				(185,316		)

	General and administrative	(17,965		)		—				—				(17,965		)

	Interest and other income (expense)	(62,814		)		—				—				(62,814		)

	Income (loss) before income taxes and equity in earnings of subsidiaries	(88,642		)		3,413				—				(85,229		)

Benefit from income taxes	32,603				—				—				32,603

Equity in earnings of subsidiaries	3,413				—				(3,413		)		—

Net income (loss)	$	(52,626	)		$	3,413			$	(3,413	)		$	(52,626	)



	Nine Months Ended September 30, 2012
	Parent				Guarantor				Intercompany				Consolidated
	Issuer				Subsidiaries				Eliminations
	(in thousands)
Operating and other revenues	$	502,175			$	18,219			$	—			$	520,394

Operating expenses	(461,243		)		(14,219		)		—				(475,462		)

General and administrative	(51,441		)		—				—				(51,441		)

Interest and other income (expense)	(14,869		)		—				—				(14,869		)

Income (loss) before income taxes and equity in earnings of subsidiaries	(25,378		)		4,000				—				(21,378		)

Benefit from income taxes	7,943				—				—				7,943

Equity in earnings of subsidiaries	4,000				—				(4,000		)		—

Net income (loss)	$	(13,435	)		$	4,000			$	(4,000	)		$	(13,435	)

Schedule of Condensed Consolidating Statements of Comprehensive Income	'
	Condensed Consolidating Statements of Comprehensive Income (Loss)



		Three Months Ended September 30, 2013
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Net income (loss)	$	(166,656	)		$	4,837			$	(4,837	)		$	(166,656	)

	Other Comprehensive Loss, net of tax:
	Effect of derivative financial instruments	(1,186		)		—				—				(1,186		)

	Other comprehensive loss	(1,186		)		—				—				(1,186		)

	Comprehensive income (loss)	$	(167,842	)		$	4,837			$	(4,837	)		$	(167,842	)


		Nine Months Ended September 30, 2013
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Net income (loss)	$	(185,534	)		$	11,707			$	(11,707	)		$	(185,534	)

	Other Comprehensive Loss, net of tax:
	Effect of derivative financial instruments	(3,688		)		—				—				(3,688		)

	Other comprehensive loss	(3,688		)		—				—				(3,688		)

	Comprehensive income (loss)	$	(189,222	)		$	11,707			$	(11,707	)		$	(189,222	)



		Three Months Ended September 30, 2012
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Net income (loss)	$	(52,626	)		$	3,413			$	(3,413	)		$	(52,626	)

	Other Comprehensive Loss, net of tax:
	Effect of derivative financial instruments	(12,739		)		—				—				(12,739		)

	Other comprehensive loss	(12,739		)		—				—				(12,739		)

	Comprehensive income (loss)	$	(65,365	)		$	3,413			$	(3,413	)		$	(65,365	)


		Nine Months Ended September 30, 2012
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Net income (loss)	$	(13,435	)		$	4,000			$	(4,000	)		$	(13,435	)

	Other Comprehensive Loss, net of tax:
	Effect of derivative financial instruments	(41,644		)		—				—				(41,644		)

	Other comprehensive loss	(41,644		)		—				—				(41,644		)

	Comprehensive income (loss)	$	(55,079	)		$	4,000			$	(4,000	)		$	(55,079	)

Schedule of Condensed Consolidating Statements of Cash Flows	'
	Condensed Consolidating Statements of Cash Flows



		Nine Months Ended September 30, 2013
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Cash flows from operating activities	$	179,003			$	17,299			$	—			$	196,302

	Cash flows from investing activities:
	Additions to oil and gas properties, including acquisitions	(303,366		)		(32,231		)		—				(335,597		)

	Additions to furniture, fixtures and other	(1,506		)		—				—				(1,506		)

	Proceeds from sale of properties and other investing activities	784				—				—				784

	Cash flows from financing activities:
	Proceeds from debt	390,000				—				—				390,000

	Principal and redemption premium payments on debt	(269,125		)		—				—				(269,125		)

	Intercompany transfers	(14,932		)		14,932				—				—

	Other financing activities	227				—				—				227

	Change in cash and cash equivalents	(18,915		)		—				—				(18,915		)

	Beginning cash and cash equivalents	79,395				50				—				79,445

	Ending cash and cash equivalents	$	60,480			$	50			$	—			$	60,530




		Nine Months Ended September 30, 2012
		Parent				Guarantor				Intercompany				Consolidated
		Issuer				Subsidiaries				Eliminations
		(in thousands)
	Cash flows from operating activities	$	284,188			$	6,415			$	—			$	290,603

	Cash flows from investing activities:
	Additions to oil and gas properties, including acquisitions	(727,818		)		(23,727		)		—				(751,545		)

	Additions to furniture, fixtures and other	(5,519		)		—				—				(5,519		)

	Proceeds from sale of properties and other investing activities	91				—				—				91

	Cash flows from financing activities:
	Proceeds from debt	785,826				—				—				785,826

	Principal and redemption premium payments on debt	(343,163		)		—				—				(343,163		)

	Intercompany transfers	(17,312		)		17,312				—				—

	Other financing activities	(9,691		)		—				—				(9,691		)

	Change in cash and cash equivalents	(33,398		)		—				—				(33,398		)

	Beginning cash and cash equivalents	57,281				50				—				57,331

	Ending cash and cash equivalents	$	23,883			$	50			$	—			$	23,933

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Summary Of Significant Accounting Policies [Line Items]	'	'	'	'
Conversion ratio	'	'	'one barrel to six Mcfe	'
Shares of stock options and nonvested performance-based equity shares of common stock	2,450,539	3,799,612	2,731,578	3,829,825
5% Convertible Senior Notes Due 2028	'	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'	'
Debt, stated interest rate	5.00%	'	5.00%	'
Debt maturity date	'2028	'	'2028	'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Summary of Accounts Receivable (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Allowance for doubtful accounts	($23)	($325)
Accounts receivable	99,537	112,011
Accrued Oil, Gas, and NGL Sales	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accounts receivable gross	68,013	69,482
Due from Joint Interest Owners	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accounts receivable gross	28,489	36,300
Other	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accounts receivable gross	$3,058	$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 $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Accounting Policies [Abstract]	'		'
Proved properties	$422,083		$387,242
Wells and related equipment and facilities	2,080,178		2,625,891
Support equipment and facilities	163,242		304,914
Materials and supplies	10,193		13,220
Total proved oil and gas properties	2,675,696		3,331,267
Unproved properties	307,557		384,486
Wells and facilities in progress	54,829		72,721
Total unproved oil and gas properties, excluded from amortization	362,386		457,207
Oil and gas properties held-for-sale, net	378,449	[1]	0
Accumulated depreciation, depletion, amortization and impairment	-907,222		-1,203,495
Total oil and gas properties, net	$2,509,309		$2,584,979

[1]	The oil and gas properties held for sale balance shown in this table is different from the balance on the Unaudited Consolidated Balance Sheet because it does not include $4.1 million of furniture, equipment and other, net.

Summary_of_Significant_Account6

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Net Capitalized Costs and Associated Accumulated Depreciation, Depletion & Amortization and Non Cash Impairments (Parenthetical) (Details) (USD $)	Sep. 30, 2013
Accounting Policies [Abstract]	'
Assets Held-for-sale, Furniture, Equipment and Other, net	$4.10

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 $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Summary Of Significant Accounting Policies [Line Items]	'		'		'		'
Non-cash impairment of oil and gas properties	'		'		$216,600,000		'
Long Lived Assets Held-for-sale, Impairment Charge	201,300,000		'		201,300,000		'
Dry hole costs	-36,000		15,658,000		928,000		15,891,000
Abandonment expense	2,835,000		4,110,000		10,154,000		7,179,000
Total non-cash impairment, dry hole costs and abandonment expense	219,363,000		38,540,000		227,646,000		60,179,000
Unproved properties, no future development plans [Member]	'		'		'		'
Summary Of Significant Accounting Policies [Line Items]	'		'		'		'
Non-cash impairment of oil and gas properties	'		'		15.3		18.3
Proved Oil And Gas Properties [Member]	'		'		'		'
Summary Of Significant Accounting Policies [Line Items]	'		'		'		'
Non-cash impairment of oil and gas properties	198,787,000	[1]	0		198,787,000	[1]	0
Unproved Oil And Gas Properties [Member]	'		'		'		'
Summary Of Significant Accounting Policies [Line Items]	'		'		'		'
Non-cash impairment of oil and gas properties	17,777,000	[2]	18,772,000	[3]	17,777,000	[2]	37,109,000	[3]
Long Lived Assets Held-for-sale, Impairment Charge	$2.50		'		$2.50		'

[1]	Non-cash impairment of proved oil and gas properties for the three and nine months ended September 30, 2013 related to assets classified as held for sale at September 30, 2013. The impairment was the result of an analysis of the carrying value of the related properties relative to their estimated fair values.
[2]	Non-cash impairment of unproved oil and gas properties for the three and nine months ended September 30, 2013 was comprised of $15.3 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 unproved properties held for sale at September 30, 2013.
[3]	Non-cash impairment of unproved oil and gas properties for the three months ended September 30, 2012 of $18.8 million 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. The additional $18.3 million unproved oil and gas properties impairment expense for the nine months ended September 30, 2012 also related to unproved oil and gas properties within other exploration and development projects primarily as a result of unfavorable market conditions or no future plans to evaluate the remaining acreage.

Summary_of_Significant_Account8

Summary of Significant Accounting Policies - Accounts Payable and Accrued Liabilities (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounting Policies [Abstract]	'	'
Accrued drilling, completion and facility costs	$63,618	$42,094
Accrued lease operating, gathering, transportation and processing expenses	19,481	16,862
Accrued general and administrative expenses	8,542	13,054
Trade payables and other	31,768	53,007
Total accounts payable and accrued liabilities	$123,409	$125,017

Summary_of_Significant_Account9

Summary of Significant Accounting Policies - Calculation of Basic and Diluted Earnings (Loss) Per Share (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounting Policies [Abstract]	'	'	'	'	'
Net income (loss)	($166,656)	($52,626)	($185,534)	($13,435)	$582
Basic weighted-average common shares outstanding in period	47,535,124	47,230,473	47,452,865	47,172,656	'
Add dilutive effects of stock options and nonvested equity shares of common stock	0	0	0	0	'
Diluted weighted-average common shares outstanding in period	47,535,124	47,230,473	47,452,865	47,172,656	'
Net Loss Per Common Share, Basic	($3.51)	($1.11)	($3.91)	($0.28)	'
Net Loss Per Common Share, Diluted	($3.51)	($1.11)	($3.91)	($0.28)	'

Supplemental_Disclosures_of_Ca2

Supplemental Disclosures of Cash Flow Information - Supplemental Cash Flow Information (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Supplemental Cash Flow Information [Abstract]	'	'
Cash paid for interest, net of amount capitalized	$61,796	$49,040
Cash paid for income taxes	1,861	11
Supplemental disclosures of non-cash investing and financing activities:	'	'
Current liabilities	75,265	75,092
Net increase in asset retirement obligations	2,924	280
Retirement of treasury stock	($1,415)	($2,430)

Divestitures_and_Assets_Held_f2

Divestitures and Assets Held for Sale- Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2013
Proceeds from Divestiture of Businesses	$325,300,000	'
Cash proceeds and recognized pre-tax loss	4,500,000	'
Long Lived Assets Held-for-sale, Impairment Charge	'	201,300,000
Percent of Financing Obligation held-for-sale	'	51.00%
Wind River Basin [Member]	'	'
Percentage Of Assets Sold	100.00%	'
Powder River Basin [Member]	'	'
Percentage Of Assets Sold	100.00%	'
Unproved Oil And Gas Properties [Member]	'	'
Long Lived Assets Held-for-sale, Impairment Charge	'	2,500,000
Proved Oil And Gas Properties [Member]	'	'
Long Lived Assets Held-for-sale, Impairment Charge	'	$198,800,000

Divestitures_and_Assets_Held_f3

Divestitures and Assets Held for Sale Asset Held for Sale (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Long Lived Assets Held-for-sale [Line Items]	'	'
Oil and gas properties held for sale, net	$382,554	$0
Asset retirement obligation held-for-sale	13,082	'
Financing obligation held-for-sale	46,363	'
Liabilities associated with assets held for sale	59,445	0
Net assets held-for-sale	323,109	'
Proved Oil And Gas Properties [Member]	'	'
Long Lived Assets Held-for-sale [Line Items]	'	'
Oil and gas properties held for sale, net	1,070,400	'
Unproved Oil And Gas Properties [Member]	'	'
Long Lived Assets Held-for-sale [Line Items]	'	'
Oil and gas properties held for sale, net	12,469	'
Furniture and Fixtures [Member]	'	'
Long Lived Assets Held-for-sale [Line Items]	'	'
Oil and gas properties held for sale, net	4,205	'
Accumulated depreciation, depletion, amortization and impairment [Member]	'	'
Long Lived Assets Held-for-sale [Line Items]	'	'
Oil and gas properties held for sale, net	($704,520)	'

LongTerm_Debt_Outstanding_Debt

Long-Term Debt - Outstanding Debt (Detail) (USD $)	9 Months Ended
Long-Term Debt - Outstanding Debt (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Jul. 08, 2009
Debt Instrument [Line Items]	'		'		'
Principal amount of debt instrument	$1,255,243,000	[1]	$1,163,863,000		'
Discount	0	[1]	-7,209,000		'
Amount	1,255,243,000	[1]	1,156,654,000		'
Amended Credit Facility	'		'		'
Debt Instrument [Line Items]	'		'		'
Maturity Date	31-Oct-16	[2]	'		'
Principal amount of debt instrument	390,000,000	[2]	0	[2]	'
Discount	0	[2]	0	[2]	'
Amount	390,000,000	[2]	0	[2]	'
9.875% Senior Notes	'		'		'
Debt Instrument [Line Items]	'		'		'
Maturity Date	15-Jul-16	[3]	'		'
Principal amount of debt instrument	0	[3]	250,000,000	[3]	250,000,000
Discount	0	[3]	-7,209,000	[3]	'
Amount	0	[3]	242,791,000	[3]	'
Convertible Notes	'		'		'
Debt Instrument [Line Items]	'		'		'
Maturity Date	15-Mar-28	[4],[5]	'		'
Principal amount of debt instrument	25,344,000	[4]	25,344,000	[4]	'
Discount	0	[4]	0	[4]	'
Amount	25,344,000	[4]	25,344,000	[4]	'
7.625% Senior Notes	'		'		'
Debt Instrument [Line Items]	'		'		'
Maturity Date	1-Oct-19	[6]	'		'
Principal amount of debt instrument	400,000,000	[6]	400,000,000	[6]	'
Discount	0	[6]	0	[6]	'
Amount	400,000,000	[6]	400,000,000	[6]	'
7.0% Senior Notes	'		'		'
Debt Instrument [Line Items]	'		'		'
Maturity Date	15-Oct-22	[7]	'		'
Principal amount of debt instrument	400,000,000	[7]	400,000,000	[7]	'
Discount	0	[7]	0	[7]	'
Amount	400,000,000	[7]	400,000,000	[7]	'
Lease Financing Obligation	'		'		'
Debt Instrument [Line Items]	'		'		'
Maturity Date	10-Aug-20	[8]	'		'
Principal amount of debt instrument	44,453,000	[8]	97,596,000	[8]	'
Discount	0	[8]	0	[8]	'
Amount	44,453,000	[8]	97,596,000	[8]	'
Long-term Debt	'		'		'
Debt Instrument [Line Items]	'		'		'
Principal amount of debt instrument	1,259,797,000		1,172,940,000		'
Discount	0		-7,209,000		'
Amount	1,259,797,000		1,165,731,000		'
Current Portion of Long-Term Debt	'		'		'
Debt Instrument [Line Items]	'		'		'
Principal amount of debt instrument	4,554,000		9,077,000		'
Discount	0		0		'
Amount	$4,554,000		$9,077,000		'

[1]	The total long-term debt balance excludes $46.4 million related to the Lease Financing Obligation that is included in liabilities associated with assets held for sale in the Unaudited Consolidated Balance Sheet. See Note 4 for additional information.
[2]	The recorded value of the Amended Credit Facility approximates its fair value due to its floating rate structure.
[3]	The aggregate estimated fair value of the 9.875% Senior Notes was $271.9 million as of DecemberÂ 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 $25.2 million and $25.3 million as of SeptemberÂ 30, 2013 and DecemberÂ 31, 2012, respectively, based on reported market trades of these instruments.
[5]	The Company has the right at any time, with at least 30 daysâ€™ notice, to call the Convertible Notes, and the holders have the right to require the Company to purchase the notes on each of MarchÂ 20, 2015,Â MarchÂ 20, 2018 and MarchÂ 20, 2023.
[6]	The aggregate estimated fair value of the 7.625% Senior Notes was approximately $410.0 million and $435.0 million as of SeptemberÂ 30, 2013 and DecemberÂ 31, 2012, respectively, based on reported market trades of these instruments.
[7]	The aggregate estimated fair value of the 7.0% Senior Notes was approximately $390.0 million and $413.8 million as of SeptemberÂ 30, 2013 and DecemberÂ 31, 2012, respectively, based on reported market trades of these instruments.
[8]	The aggregate estimated fair value of the full Lease Financing Obligation was approximately $88.1 million as of SeptemberÂ 30, 2013, 51% of which is held for sale at September 30, 2013, and $97.7 million as of DecemberÂ 31, 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_Outstanding_Debt1

Long-Term Debt - Outstanding Debt (Parenthetical) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Debt Instrument [Line Items]	'	'	'
Debt, fair value	800,000,000	$1,120,700,000	'
Percent of Financing Obligation held-for-sale	51.00%	'	'
Financing obligation held-for-sale	46,363,000	'	'
9.875% Senior Notes	'	'	'
Debt Instrument [Line Items]	'	'	'
Debt, fair value	'	271,900,000	'
Debt, stated interest rate	9.88%	9.88%	9.88%
7.625% Senior Notes	'	'	'
Debt Instrument [Line Items]	'	'	'
Debt, fair value	410,000,000	435,000,000	'
Debt, stated interest rate	7.63%	7.63%	7.63%
7.0% Senior Notes	'	'	'
Debt Instrument [Line Items]	'	'	'
Debt, fair value	390,000,000	413,800,000	'
Debt, stated interest rate	7.00%	7.00%	7.00%
Lease Financing Obligation	'	'	'
Debt Instrument [Line Items]	'	'	'
Debt, fair value	88,100,000	97,700,000	'
Convertible Notes	'	'	'
Debt Instrument [Line Items]	'	'	'
Debt, stated interest rate	5.00%	5.00%	'
Aggregate fair value of convertible notes	25,200,000	$25,300,000	'

LongTerm_Debt_Additional_Infor

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

3 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Mar. 20, 2012

Sep. 30, 2013

Mar. 12, 2008

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Jul. 08, 2009

Sep. 30, 2013

Sep. 27, 2011

Sep. 30, 2013

Mar. 12, 2012

Jul. 23, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Minimum

Maximum

5% Convertible Senior Notes Due 2028

Convertible Notes

Amended Credit Facility

9.875% Senior Notes

7.625% Senior Notes Due 2019 [Member]

7.0% Senior Notes Due 2022 [Member]

Lease Financing Obligation

7.625% Senior Notes

7.0% Senior Notes

Debt Instrument [Line Items]

Percent of Financing Obligation held-for-sale

51.00%

Line of credit facility, maximum borrowing capacity

$825,000,000

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%

Debt instrument, maturity date

15-Mar-28

31-Oct-16

[1]

15-Jul-16

[2]

1-Oct-19

15-Oct-22

10-Aug-20

[3]

1-Oct-19

[4]

15-Oct-22

[5]

Commitment fee percentage

0.38%

0.50%

Average annual interest rates incurred on Amended Credit Facility

2.10%

1.80%

2.00%

1.90%

Borrowing base determination

The borrowing base is required to be re-determined twice per year.

Line of credit facility, maximum amount outstanding during period

390,000,000

Letters of credit issued amount

26,000,000

Line of credit facility, reduced borrowing capacity

409,000,000

Principal amount

1,255,243,000

[6]

1,255,243,000

[6]

1,163,863,000

172,500,000

25,300,000

390,000,000

[1]

[2]

250,000,000

[2]

250,000,000

400,000,000

44,453,000

[3]

97,596,000

[3]

400,000,000

[4]

400,000,000

[4]

400,000,000

[5]

400,000,000

[5]

Debt discount

[6]

7,209,000

[1]

[2]

7,209,000

[2]

[3]

[4]

[5]

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

Face Amount of Outstanding Convertible Notes Repaid

147,200,000

Percentage of notes put to company

85.00%

Debt, stated interest rate

5.00%

9.88%

7.63%

7.00%

7.63%

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

100,800,000

Purchase of equipment

$36,600,000

Weighted average implicit rate based on interest expense

3.30%

[1]

The recorded value of the Amended Credit Facility approximates its fair value due to its floating rate structure.

[2]

The aggregate estimated fair value of the 9.875% Senior Notes was $271.9 million as of DecemberÂ 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 full Lease Financing Obligation was approximately $88.1 million as of SeptemberÂ 30, 2013, 51% of which is held for sale at September 30, 2013, and $97.7 million as of DecemberÂ 31, 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.

[4]

The aggregate estimated fair value of the 7.625% Senior Notes was approximately $410.0 million and $435.0 million as of SeptemberÂ 30, 2013 and DecemberÂ 31, 2012, respectively, based on reported market trades of these instruments.

[5]

The aggregate estimated fair value of the 7.0% Senior Notes was approximately $390.0 million and $413.8 million as of SeptemberÂ 30, 2013 and DecemberÂ 31, 2012, respectively, based on reported market trades of these instruments.

[6]

The total long-term debt balance excludes $46.4 million related to the Lease Financing Obligation that is included in liabilities associated with assets held for sale in the Unaudited Consolidated Balance Sheet. See Note 4 for additional information.

LongTerm_Debt_Cash_and_NonCash

Long-Term Debt - Cash and Non-Cash Portion of Interest Expense Related to Long Term Debt (Detail) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Amended Credit Facility interest	$2,296	[1]	$1,453	[1]	$4,211	[1]	$3,707	[1]
Non-cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Amended Credit Facility interest	585	[1]	586	[1]	1,756	[1]	1,757	[1]
9.875% Senior Notes \| Cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Senior Notes interest	1,029	[2]	6,172	[2]	13,373	[2]	18,516	[2]
9.875% Senior Notes \| Non-cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Senior Notes interest	0	[2]	657	[2]	1,361	[2]	1,911	[2]
Convertible Notes \| Cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Convertible Notes interest	310	[3]	317	[3]	943	[3]	2,585	[3]
Convertible Notes \| Non-cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Convertible Notes interest	1	[3]	1	[3]	4	[3]	1,770	[3]
7.625% Senior Notes \| Cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Senior Notes interest	7,625	[4]	7,625	[4]	22,875	[4]	22,875	[4]
7.625% Senior Notes \| Non-cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Senior Notes interest	272	[4]	262	[4]	798	[4]	803	[4]
7.0% Senior Notes \| Cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Senior Notes interest	7,000	[5]	7,000	[5]	21,000	[5]	15,397	[5]
7.0% Senior Notes \| Non-cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Senior Notes interest	203	[5]	197	[5]	592	[5]	464	[5]
Lease Financing Obligation \| Cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Financial Obligation interest	750	[6]	548	[6]	2,305	[6]	548	[6]
Lease Financing Obligation \| Non-cash interest [Member]	'		'		'		'
Debt Instrument [Line Items]	'		'		'		'
Financial Obligation interest	$8	[6]	$6	[6]	$24	[6]	$6	[6]

[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%Â per annum with an effective interest rate of 11.2%Â 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%Â 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 be the effective interest rate of the $25.3 million remaining principal balance, as the related debt discount was fully amortized as of MarchÂ 31, 2012.
[4]	The stated interest rate for the 7.625% Senior Notes is 7.625%Â per annum with an effective interest rate of 8.0%Â per annum.
[5]	The stated interest rate for the 7.0% Senior Notes is 7.0%Â per annum with an effective interest rate of 7.2%Â per annum.
[6]	The effective interest rate for the Lease Financing Obligation is 3.3%Â per annum.

LongTerm_Debt_Cash_and_NonCash1

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

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Jul. 08, 2009

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Mar. 12, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

9.875% Senior Notes

7.625% Senior Notes

7.0% Senior Notes Due 2022 [Member]

7.0% Senior Notes

Lease Financing Obligation

5% Convertible Notes [Member]

Debt Instrument [Line Items]

Debt, stated interest rate

9.88%

7.63%

7.00%

5.00%

Effective interest rate of debt instrument

11.20%

8.00%

7.20%

3.30%

Principal amount of debt instrument

$1,255,243,000

[1]

$1,163,863,000

[2]

$250,000,000

[2]

$250,000,000

$400,000,000

[3]

$400,000,000

[3]

$400,000,000

[4]

$400,000,000

[4]

$44,453,000

[5]

$97,596,000

[5]

$25,300,000

[1]

[2]

[3]

[4]

[5]

Asset_Retirement_Obligations_S

Asset Retirement Obligations - Schedule of Asset Retirement Obligations (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Asset retirement obligation held-for-sale	$13,082
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'
As of December 31, 2012	47,616
Liabilities incurred	2,095
Liabilities settled	-824
Disposition of properties	-387
Accretion expense	2,604
Revisions to estimate	1,218
As of June 30, 2013	52,322
Less: current asset retirement obligations	948
Long-term asset retirement obligations	$38,292

Fair_Value_Measurements_Fair_V

Fair Value Measurements - Fair Value, Balance Sheet Grouping (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Assets	'	'	'	'
Deferred Compensation Plan	$920	$966	'	'
Cash Equivalents - Money Market Funds	60,530	79,445	23,933	57,331
Cash Equivalents - Money Market Funds	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	53	53	'	'
Commodity Derivatives	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	16,881	40,432	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	11,804	7,875	'	'
Level 1	'	'	'	'
Assets	'	'	'	'
Deferred Compensation Plan	920	966	'	'
Level 1 \| Cash Equivalents - Money Market Funds	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	53	53	'	'
Level 1 \| Commodity Derivatives	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	0	0	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	0	0	'	'
Level 2	'	'	'	'
Assets	'	'	'	'
Deferred Compensation Plan	0	0	'	'
Level 2 \| Cash Equivalents - Money Market Funds	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	0	0	'	'
Level 2 \| Commodity Derivatives	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	16,881	40,432	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	11,804	7,875	'	'
Level 3	'	'	'	'
Assets	'	'	'	'
Deferred Compensation Plan	0	0	'	'
Level 3 \| Cash Equivalents - Money Market Funds	'	'	'	'
Assets	'	'	'	'
Cash Equivalents - Money Market Funds	0	0	'	'
Level 3 \| Commodity Derivatives	'	'	'	'
Assets	'	'	'	'
Commodity Derivatives, Assets	0	0	'	'
Liabilities	'	'	'	'
Fair value liabilities disclosure	$0	$0	'	'

Fair_Value_Measurements_Additi

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

9 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

9.875% Senior Notes

7.625% Senior Notes

7.0% Senior Notes

Amended Credit Facility

Convertible Notes

Lease Financing Obligation

Fair Value Measurements [Line Items]

Debt, stated interest rate

9.88%

7.63%

7.00%

Debt, fair value

$800,000,000

$1,120,700,000

$271,900,000

$410,000,000

$435,000,000

$390,000,000

$413,800,000

$390,000,000

$25,200,000

$25,300,000

$88,100,000

$97,700,000

Non-cash impairment of oil and gas properties

216,600,000

Long Lived Assets Held-for-sale, Impairment Charge

$201,300,000

Derivative_Instruments_Fair_Va

Derivative Instruments - Fair Value Amounts of Derivative Instruments (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Assets	$16,881		$40,432
Gross Amounts Offset in the Balance Sheet	-9,533		-7,471
Net Amounts of Assets Presented in the Balance Sheet	7,348		32,961
Gross Amounts of Recognized Liabilities	-11,804		-7,875
Gross Amounts Offset in the Balance Sheet	9,533		7,471
Net Amounts of Liabilities Presented in the Balance Sheet	-2,271		-404
Derivative Assets	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Assets	12,217		34,828
Gross Amounts Offset in the Balance Sheet	-8,711	[1]	-4,848	[1]
Net Amounts of Assets Presented in the Balance Sheet	3,506		29,980
Deferred Financing Costs, Derivative Assets and Other Non Current Assets	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Assets	4,664		5,604
Gross Amounts Offset in the Balance Sheet	-822	[1]	-2,623	[1]
Net Amounts of Assets Presented in the Balance Sheet	3,842	[2]	2,981	[2]
Derivative Liabilities	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Liabilities	-10,982		-4,848
Gross Amounts Offset in the Balance Sheet	8,711	[3]	4,848	[3]
Net Amounts of Liabilities Presented in the Balance Sheet	-2,271		0
Derivative and Other Non Current Liabilities	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Amounts of Recognized Liabilities	-822		-3,027
Gross Amounts Offset in the Balance Sheet	822	[3]	2,623	[3]
Net Amounts of Liabilities Presented in the Balance Sheet	$0		($404)	[4]

[1]	Amounts are netted against derivative asset balances with the same counterparty, and therefore, are presented as a net asset on the Unaudited Consolidated Balance Sheets.
[2]	As of SeptemberÂ 30, 2013 and DecemberÂ 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $20.2 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 Unaudited Consolidated Balance Sheets.
[4]	As of DecemberÂ 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $4.1 million of other noncurrent liabilities.

Derivative_Instruments_Fair_Va1

Derivative Instruments - Fair Value Amounts of Derivative Instruments (Parenthetical) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]	'	'
Balance included in other noncurrent liabilities excluding deferred financing costs and other noncurrent assets	$20.20	$26.80
Derivative Liabilities	'	'
Derivatives, Fair Value [Line Items]	'	'
Balance included in other noncurrent liabilities excluding hedge instruments	'	$4.10

Derivative_Instruments_Cash_Fl

Derivative Instruments - Cash Flow Hedge Gain and Losses (Detail) (USD $)	3 Months Ended				9 Months Ended				12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'		'		'
Effect of derivative financial instruments, taxes	$700		$7,700		$2,216		$25,000		$30,458
Commodity Derivatives	'		'		'		'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'		'		'
Derivative Qualifying as Cash flow Hedges	'		'		'CommodityÂ Hedges		'		'
Amount of Gain (Loss) Reclassified from AOCI into Income (net of tax)	$1,186	[1],[2]	$12,739	[1],[2]	$3,688	[1],[2]	$41,644	[1],[2]	'

[1]	Presented net of income tax expense of $0.7 million and $7.7 million for the three months ended SeptemberÂ 30, 2013 and 2012, respectively, and $2.2 million and $25.0 million for the nine months ended SeptemberÂ 30, 2013 and 2012, respectively.
[2]	Gains reclassified from AOCI into income are included in the oil, gas and NGL production revenues in the Unaudited Consolidated Statements of Operations.

Derivative_Instruments_Financi

Derivative Instruments - Financial Instruments for Hedging Volume (Detail)	Sep. 30, 2013
	MMBTU
	bbl
October-December 2013	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Oil (Bbls)	806,300
Natural Gas (MMbtu)	11,355,000
Natural Gas Liquids (Bbls)	98,214
2014	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Oil (Bbls)	2,972,200
Natural Gas (MMbtu)	30,415,000
Natural Gas Liquids (Bbls)	35,714
2015	'
Derivative Instruments, Gain (Loss) [Line Items]	'
Oil (Bbls)	401,200
Natural Gas (MMbtu)	3,650,000
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, USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Oil and Natural Gas Derivative Instruments	'		'		'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'		'
Commodity derivative settlements on derivatives designated as cash flow hedges	$1,899	[1]	$20,391	[1]	$5,902	[1]	$66,654	[1]
Total commodity derivative gain (loss)	($25,595)	[2]	($38,340)	[2]	($18,607)	[2]	$53,431	[2]

[1]	Included in oil, gas and NGL production revenues in the Unaudited Consolidated Statements of Operations.
[2]	Included in commodity derivative gain (loss) in the Unaudited Consolidated Statements of Operations.

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
	Counterparty
Derivative Instruments And Hedging Activities [Line Items]	'
Number of counterparties for hedges at period end	11

Equity_Incentive_Compensation_2

Equity Incentive Compensation Plans and Other Employee Benefits - Non-Cash Stock-Based Compensation Cost Related to Equity Awards (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Stock Based Compensation [Line Items]	'	'	'	'
Non-cash stock-based compensation equity awards	$3,232,000	$4,080,000	$11,847,000	$12,330,000
Common Stock Options	'	'	'	'
Stock Based Compensation [Line Items]	'	'	'	'
Non-cash stock-based compensation equity awards	681,000	1,626,000	3,898,000	5,299,000
Nonvested Equity Common Stock	'	'	'	'
Stock Based Compensation [Line Items]	'	'	'	'
Non-cash stock-based compensation equity awards	1,562,000	1,711,000	5,550,000	5,485,000
Nonvested Equity Common Stock Units	'	'	'	'
Stock Based Compensation [Line Items]	'	'	'	'
Non-cash stock-based compensation equity awards	277,000	371,000	989,000	371,000
Nonvested Performance-Based Equity	'	'	'	'
Stock Based Compensation [Line Items]	'	'	'	'
Non-cash stock-based compensation equity awards	$712,000	$372,000	$1,410,000	$1,175,000

Equity_Incentive_Compensation_3

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

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Feb. 29, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2010

Dec. 31, 2012

Feb. 28, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Feb. 28, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Feb. 28, 2013

Sep. 30, 2013

Sep. 30, 2012

Feb. 28, 2013

Feb. 28, 2012

Sep. 30, 2013

Performance-Based Awards

Two Thousand And Ten Performance Program (2011 Performance)

Two Thousand And Ten Performance Program (2012 Performance)

2012 Performance Program

Two Thousand And Thirteen Performance Program

2010 Performance Program

Two Thousand And Ten Performance Program (2013 TSR Performance)

Two Thousand And Ten Performance Program (2013 Performance)

Maximum

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

Unrecognized compensation cost

$22,200,000

Weighted-average period (years)

'2 years 4 months 24 days

Supplemental grant percentage of performance based shares

26.60%

Non-cash stock based compensation

3,232,000

4,080,000

11,847,000

12,330,000

200,000

100,000

300,000

100,000

300,000

100,000

700,000

400,000

800,000

100,000

300,000

Weighted Percentage Of Stockholders Return Related To Performance Goals

33.30%

40.00%

Performance goals percentage change in discretionary cash flow

30.00%

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

30.00%

Additional performance based nonvested equity shares

86,223

Additional performance based nonvested equity shares

22,710

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

25.00%

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

50.00%

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

100.00%

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

200.00%

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

200.00%

Performance shares set as side at the end of plan

100,434

388,420

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

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

400,000

1,600,000

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

6.00%

Deferred Compensation Liability, Non Current

900,000

1,000,000

Deferred Compensation Liability, Current

$500,000

$300,000

Equity_Incentive_Compensation_4

Equity Incentive Compensation Plans and Other Employee Benefits - Stock Options and Nonvested Equity Shares, Equity Awards Granted (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'	'	'
Options to purchase shares of common stock, Number of Options	0	26,602	0	582,284
Options to purchase shares of common stock, Weighted Average Price Per Share	$0	$20.23	$0	$27.16
Nonvested equity shares, Number of Shares	57,792	31,664	615,052	260,778
Nonvested equity common stock units, Number of Shares	2,210	52,917	54,429	52,917
Nonvested performance-based equity shares, Number of Shares	154,314	3,400	442,300	179,987
Total shares granted	214,316	87,981	1,111,781	493,682
Nonvested equity shareps	$22.36	$21.64	$17.80	$26.06
Nonvested equity common stock units, Weighted Average Grant Date Fair Value	$25.11	$18.94	$22.17	$18.94
Nonvested performance-based equity shares, Weighted Average Grant Date Fair Value	$20.86	$23.48	$18.08	$26.26

Equity_Incentive_Compensation_5

Equity Incentive Compensation Plans and Other Employee Benefits - Stock Options and Nonvested Equity Shares, Equity Awards Granted (Parenthetical) (Detail) (USD $)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Cash and common stock contributions	$0.40	$1.60
Two Thousand And Thirteen Performance Program	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Weighted Percentage Of Stockholders Return Related To Performance Goals	'	33.30%
Performance Goals Percentage for Change In Discretionary Cash Flow Per Debt Adjusted Share Relative To Defined Peer Groups Percentage	'	33.30%
Performance Goals Percentage Weight For Change in Proved Natural Gas And Oil Reserves Per Debt Adjusted Share	'	33.30%

Equity_Incentive_Compensation_6

Equity Incentive Compensation Plans and Other Employee Benefits - Director Fees (Detail) (Director, USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Director	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Director fees (shares)	2,210	3,732	14,116	6,907
Stock-based compensation (in thousand)	$56	$92	$297	$167

Commitments_and_Contingencies_1

Commitments and Contingencies - Schedule of Aggregate Undiscounted Minimum Future Lease Payments (Detail) (Lease Financing Obligation, USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified	Sep. 30, 2013
Lease Financing Obligation	'
Future Minimum Lease Payments Under Capital Leases And Operating Leases For Continuing Operations [Line Items]	'
2013	$3,034
2014	12,139
2015	12,139
2016	12,139
2017	12,139
Thereafter	32,368
Total	$83,958	[1]

[1]	The balance shown in this table includes the approximately 51% of the Lease Financing Obligation that the purchaser will assume upon closing of the West Tavaputs Sale in December 2013.

Commitments_and_Contingencies_2

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
	Sep. 30, 2013	Sep. 30, 2012	Agreement	Sep. 30, 2012
Contingencies And Commitments [Line Items]	'	'	'	'
Percent of Financing Obligation held-for-sale	51.00%	'	51.00%	'
Transportation Demand Charges	$9.50	$11.30	$27.80	$33.70
Firm processing charges	1.4	1.6	3.5	4.6
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	$0.50	$0.50	$1.50	$1.50
Minimum	'	'	'	'
Contingencies And Commitments [Line Items]	'	'	'	'
Contract term, years	'2 years	'	'2 years	'
Maximum	'	'	'	'
Contingencies And Commitments [Line Items]	'	'	'	'
Contract term, years	'10 years	'	'10 years	'

Commitments_and_Contingencies_3

Commitments and Contingencies - Gross Future Minimum Transportation Demand and Firm Processing Charges (Detail) (USD $)	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Transporation Demand Charges held-for-sale	$137,700,000
2013	14,450,000
2014	57,929,000
2015	58,065,000
2016	56,464,000
2017	51,824,000
Thereafter	147,984,000
Total	$386,716,000	[1]

[1]	The balance shown in this table includes $137.7 million of transportation demand and firm processing charges that the purchaser will assume upon closing of the West Tavaputs Sale in December 2013. See Note 13.

Commitments_and_Contingencies_4

Commitments and Contingencies - Future Minimum Annual Payments under Drilling, Lease and Other Agreements (Detail) (Office & Equipment Leases, USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified	Sep. 30, 2013
Office & Equipment Leases	'
Operating Leased Assets [Line Items]	'
2013	$1,069
2014	4,561
2015	3,099
2016	2,593
2017	2,517
Thereafter	3,158
Total	$16,997

Commitments_and_Contingencies_5

Commitments and Contingencies Commitments and Contingencies - Additional Information Parenthetical (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Commitments and Contingencies Disclosure [Abstract]	'	'	'	'
Office lease expense	$0.50	$0.50	$1.50	$1.50

Guarantor_Subsidiaries_Additio

Guarantor Subsidiaries - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
	Sep. 30, 2013	9.875% Senior Notes	9.875% Senior Notes	9.875% Senior Notes	7.625% Senior Notes	7.625% Senior Notes	7.625% Senior Notes	7.0% Senior Notes	7.0% Senior Notes	7.0% Senior Notes
Guarantor Subsidiaries [Line Items]	'	'	'	'	'	'	'	'	'	'
Debt, stated interest rate	'	9.88%	9.88%	9.88%	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 $)	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets:	'	'	'
Current assets	$169,051	$228,339	'
Property and equipment, net	2,533,145	2,611,337	'
Intercompany receivable (payable)	0	0	'
Investment in subsidiaries	0	0	'
Noncurrent assets	24,065	29,773	'
Total Assets	2,726,261	2,869,449	'
Liabilities and Stockholdersâ€™ Equity:	'	'	'
Current liabilities	206,237	213,133	'
Long-term debt	1,255,243	1,156,654	'
Deferred income taxes	156,034	266,364	'
Other noncurrent liabilities	101,749	50,523	'
Stockholders' equity	1,006,998	1,182,775	1,218,838
Total liabilities and stockholders' equity	2,726,261	2,869,449	'
Parent Issuer	'	'	'
Assets:	'	'	'
Current assets	165,436	226,013	'
Property and equipment, net	2,410,495	2,514,240	'
Intercompany receivable (payable)	156,414	141,272	'
Investment in subsidiaries	-35,826	-47,533	'
Noncurrent assets	24,065	29,773	'
Total Assets	2,720,584	2,863,765	'
Liabilities and Stockholdersâ€™ Equity:	'	'	'
Current liabilities	205,331	212,117	'
Long-term debt	1,255,243	1,156,654	'
Deferred income taxes	153,847	264,113	'
Other noncurrent liabilities	99,165	48,106	'
Stockholders' equity	1,006,998	1,182,775	'
Total liabilities and stockholders' equity	2,720,584	2,863,765	'
Guarantor Subsidiaries	'	'	'
Assets:	'	'	'
Current assets	3,615	2,326	'
Property and equipment, net	122,650	97,097	'
Intercompany receivable (payable)	-156,414	-141,272	'
Investment in subsidiaries	0	0	'
Noncurrent assets	0	0	'
Total Assets	-30,149	-41,849	'
Liabilities and Stockholdersâ€™ Equity:	'	'	'
Current liabilities	906	1,016	'
Long-term debt	0	0	'
Deferred income taxes	2,187	2,251	'
Other noncurrent liabilities	2,584	2,417	'
Stockholders' equity	-35,826	-47,533	'
Total liabilities and stockholders' equity	-30,149	-41,849	'
Intercompany Eliminations	'	'	'
Assets:	'	'	'
Current assets	0	0	'
Property and equipment, net	0	0	'
Intercompany receivable (payable)	0	0	'
Investment in subsidiaries	35,826	47,533	'
Noncurrent assets	0	0	'
Total Assets	35,826	47,533	'
Liabilities and Stockholdersâ€™ Equity:	'	'	'
Current liabilities	0	0	'
Long-term debt	0	0	'
Deferred income taxes	0	0	'
Other noncurrent liabilities	0	0	'
Stockholders' equity	35,826	47,533	'
Total liabilities and stockholders' equity	$35,826	$47,533	'

Guarantor_Subsidiaries_Schedul1

Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Operations (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Operating and other revenues	$148,555	$180,866	$429,131	$520,394	'
Operating expenses	-334,223	-185,316	-568,437	-475,462	'
General and administrative	-14,402	-17,965	-48,257	-51,441	'
Interest and other income (expense)	-67,081	-62,814	-109,290	-14,869	'
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	-267,151	-85,229	-296,853	-21,378	'
Provision for (Benefit from) Income Taxes	100,495	32,603	111,319	7,943	'
Equity in earnings (loss) of subsidiaries	0	0	0	0	'
Net income (loss)	-166,656	-52,626	-185,534	-13,435	582
Parent Issuer	'	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Operating and other revenues	139,286	172,054	405,057	502,175	'
Operating expenses	-329,791	-179,917	-556,070	-461,243	'
General and administrative	-14,402	-17,965	-48,257	-51,441	'
Interest and other income (expense)	-67,081	-62,814	-109,290	-14,869	'
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	-271,988	-88,642	-308,560	-25,378	'
Provision for (Benefit from) Income Taxes	100,495	32,603	111,319	7,943	'
Equity in earnings (loss) of subsidiaries	4,837	3,413	11,707	4,000	'
Net income (loss)	-166,656	-52,626	-185,534	-13,435	'
Guarantor Subsidiaries	'	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Operating and other revenues	9,269	8,812	24,074	18,219	'
Operating expenses	-4,432	-5,399	-12,367	-14,219	'
General and administrative	0	0	0	0	'
Interest and other income (expense)	0	0	0	0	'
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	4,837	3,413	11,707	4,000	'
Provision for (Benefit from) Income Taxes	0	0	0	0	'
Equity in earnings (loss) of subsidiaries	0	0	0	0	'
Net income (loss)	4,837	3,413	11,707	4,000	'
Intercompany Eliminations	'	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Operating and other revenues	0	0	0	0	'
Operating expenses	0	0	0	0	'
General and administrative	0	0	0	0	'
Interest and other income (expense)	0	0	0	0	'
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	0	0	0	0	'
Provision for (Benefit from) Income Taxes	0	0	0	0	'
Equity in earnings (loss) of subsidiaries	-4,837	-3,413	-11,707	-4,000	'
Net income (loss)	($4,837)	($3,413)	($11,707)	($4,000)	'

Guarantor_Subsidiaries_Schedul2

Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Net income (loss)	($166,656)	($52,626)	($185,534)	($13,435)	$582
Effect of derivative financial instruments	-1,186	-12,739	-3,688	-41,644	-50,712
Other comprehensive income (loss)	-1,186	-12,739	-3,688	-41,644	'
Comprehensive Loss	-167,842	-65,365	-189,222	-55,079	'
Parent Issuer	'	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Net income (loss)	-166,656	-52,626	-185,534	-13,435	'
Effect of derivative financial instruments	-1,186	-12,739	-3,688	-41,644	'
Other comprehensive income (loss)	-1,186	-12,739	-3,688	-41,644	'
Comprehensive Loss	-167,842	-65,365	-189,222	-55,079	'
Guarantor Subsidiaries	'	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Net income (loss)	4,837	3,413	11,707	4,000	'
Effect of derivative financial instruments	0	0	0	0	'
Other comprehensive income (loss)	0	0	0	0	'
Comprehensive Loss	4,837	3,413	11,707	4,000	'
Intercompany Eliminations	'	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'	'
Net income (loss)	-4,837	-3,413	-11,707	-4,000	'
Effect of derivative financial instruments	0	0	0	0	'
Other comprehensive income (loss)	0	0	0	0	'
Comprehensive Loss	($4,837)	($3,413)	($11,707)	($4,000)	'

Guarantor_Subsidiaries_Schedul3

Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Cash Flows (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Condensed Financial Statements, Captions [Line Items]	'	'
Cash flows from operating activities	$196,302	$290,603
Cash flows from investing activities:	'	'
Additions to oil and gas properties, including acquisitions	-335,597	-751,545
Additions to furniture, fixtures and other	-1,506	-5,519
Proceeds from sale of properties and other investing activities	784	91
Cash flows from financing activities:	'	'
Proceeds from debt	390,000	785,826
Principal and redemption premium payments on debt	-269,125	-343,163
Intercompany transfers	0	0
Other financing activities	227	-9,691
Decrease in Cash and Cash Equivalents	-18,915	-33,398
Beginning Cash and Cash Equivalents	79,445	57,331
Ending Cash and Cash Equivalents	60,530	23,933
Parent Issuer	'	'
Condensed Financial Statements, Captions [Line Items]	'	'
Cash flows from operating activities	179,003	284,188
Cash flows from investing activities:	'	'
Additions to oil and gas properties, including acquisitions	-303,366	-727,818
Additions to furniture, fixtures and other	-1,506	-5,519
Proceeds from sale of properties and other investing activities	784	91
Cash flows from financing activities:	'	'
Proceeds from debt	390,000	785,826
Principal and redemption premium payments on debt	-269,125	-343,163
Intercompany transfers	-14,932	-17,312
Other financing activities	227	-9,691
Decrease in Cash and Cash Equivalents	-18,915	-33,398
Beginning Cash and Cash Equivalents	79,395	57,281
Ending Cash and Cash Equivalents	60,480	23,883
Guarantor Subsidiaries	'	'
Condensed Financial Statements, Captions [Line Items]	'	'
Cash flows from operating activities	17,299	6,415
Cash flows from investing activities:	'	'
Additions to oil and gas properties, including acquisitions	-32,231	-23,727
Additions to furniture, fixtures and other	0	0
Proceeds from sale of properties and other investing activities	0	0
Cash flows from financing activities:	'	'
Proceeds from debt	0	0
Principal and redemption premium payments on debt	0	0
Intercompany transfers	14,932	17,312
Other financing activities	0	0
Decrease in Cash and Cash Equivalents	0	0
Beginning Cash and Cash Equivalents	50	50
Ending Cash and Cash Equivalents	50	50
Intercompany Eliminations	'	'
Condensed Financial Statements, Captions [Line Items]	'	'
Cash flows from operating activities	0	0
Cash flows from investing activities:	'	'
Additions to oil and gas properties, including acquisitions	0	0
Additions to furniture, fixtures and other	0	0
Proceeds from sale of properties and other investing activities	0	0
Cash flows from financing activities:	'	'
Proceeds from debt	0	0
Principal and redemption premium payments on debt	0	0
Intercompany transfers	0	0
Other financing activities	0	0
Decrease in Cash and Cash Equivalents	0	0
Beginning Cash and Cash Equivalents	0	0
Ending Cash and Cash Equivalents	$0	$0

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Subsequent Event [Line Items]	'
Proceeds from Sale of Property, Plant, and Equipment	$371.50
Liabilities of Assets Held-for-sale	46
Long Lived Assets Held-for-sale, Impairment Charge	$201.30