10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2013

OR

o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from to

Commission file number 001-32367

BILL BARRETT CORPORATION

(Exact name of registrant as specified in its charter)

Delaware	80-0000545
(State or other jurisdiction of incorporation or organization)	(IRS Employer Identification No.)

1099 18th Street, Suite 2300 Denver, Colorado	80202
(Address of principal executive offices)	(Zip Code)

(303) 293-9100

(Registrant’s telephone number, including area code)

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    x  Yes    o  No

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    x  Yes    o  No

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer	x	Accelerated filer	o
Non-accelerated filer	o  (Do not check if a smaller reporting company)	Smaller reporting company	o

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    o  Yes    x  No

There were 48,711,632shares of $0.001 par value common stock outstanding on July 19, 2013.

INDEX TO FINANCIAL STATEMENTS

PART I. FINANCIAL INFORMATION
Item 1.	Consolidated Financial Statements (Unaudited)	3
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	29
Item 3.	Quantitative and Qualitative Disclosures about Market Risk	46
Item 4.	Controls and Procedures	47
PART II. OTHER INFORMATION
Item 1.	Legal Proceedings	47
Item 1A.	Risk Factors	47
Item 2.	Unregistered Sales of Equity Securities and Use of Proceeds	47
Item 3.	Defaults Upon Senior Securities	48
Item 4.	Mine Safety Disclosures	48
Item 5.	Other Information	48
Item 6.	Exhibits	48
SIGNATURES		48

2

PART I. FINANCIAL INFORMATION

ITEM 1. Consolidated Financial Statements.

BILL BARRETT CORPORATION

CONSOLIDATED BALANCE SHEETS

(UNAUDITED)

	June 30, 2013			December 31, 2012
	(in thousands, except share data)
Assets:
Current assets:
Cash and cash equivalents	$	62,875		$	79,445
Accounts receivable, net of allowance for doubtful accounts	95,457			112,011
Derivative assets	19,581			29,980
Prepayments and other current assets	5,311			6,903
Total current assets	183,224			228,339
Property and equipment - at cost, successful efforts method for oil and gas properties:
Proved oil and gas properties	3,601,215			3,331,267
Unproved oil and gas properties, excluded from amortization	401,217			457,207
Furniture, equipment and other	46,600			45,636
	4,049,032			3,834,110
Accumulated depreciation, depletion, amortization and impairment	(1,350,978		)	(1,222,773		)
Total property and equipment, net	2,698,054			2,611,337
Deferred financing costs and other noncurrent assets	33,889			29,773
Total	$	2,915,167		$	2,869,449
Liabilities and Stockholders’ Equity:
Current liabilities:
Accounts payable and accrued liabilities	$	120,719		$	125,017
Amounts payable to oil and gas property owners	25,532			19,663
Production taxes payable	34,866			45,624
Derivative liabilities	56			—
Deferred income taxes	12,345			13,752
Current portion of long-term debt	9,227			9,077
Total current liabilities	202,745			213,133
Long-term debt	1,232,864			1,156,654
Asset retirement obligations	49,699			46,050
Deferred income taxes	255,445			266,364
Derivatives and other noncurrent liabilities	4,592			4,473
Stockholders’ equity:
Common stock, $0.001 par value; authorized 150,000,000 shares; 48,773,806 and 48,150,475 shares issued and outstanding at June 30, 2013 and December 31, 2012, respectively, with 1,270,435 and 870,794 shares subject to restrictions, respectively	48			47
Additional paid-in capital	892,349			883,923
Retained earnings	274,595			293,473
Treasury stock, at cost: zero shares at June 30, 2013 and December 31, 2012, respectively	—			—
Accumulated other comprehensive income	2,830			5,332
Total stockholders’ equity	1,169,822			1,182,775
Total	$	2,915,167		$	2,869,449

See notes to Unaudited Consolidated Financial Statements.

3

BILL BARRETT CORPORATION

CONSOLIDATED STATEMENTS OF OPERATIONS

(UNAUDITED)

	Three Months Ended June 30,						Six Months Ended June 30,
	2013			2012			2013			2012
	(in thousands, except share and per share data)
Operating and Other Revenues:
Oil, gas and NGL production	$	140,380		$	159,490		$	274,785		$	336,532
Other	1,919			862			5,791			2,996
Total operating and other revenues	142,299			160,352			280,576			339,528
Operating Expenses:
Lease operating expense	16,112			19,030			34,858			37,668
Gathering, transportation and processing expense	18,772			25,862			34,360			53,214
Production tax expense	7,781			6,892			13,732			13,099
Exploration expense	141			4,062			236			4,501
Impairment, dry hole costs and abandonment expense	1,182			21,075			8,283			21,639
Depreciation, depletion and amortization	74,307			85,942			142,745			160,025
General and administrative expense	13,273			15,036			33,855			33,476
Total operating expenses	131,568			177,899			268,069			323,622
Operating Income (Loss)	10,731			(17,547		)	12,507			15,906
Other Income and Expense:
Interest and other income	32			113			71			75
Interest expense	(24,726		)	(23,912		)	(49,268		)	(45,502		)
Commodity derivative gain	36,839			47,024			6,988			91,771
Gain on extinguishment of debt	—			—			—			1,601
Total other income and expense	12,145			23,225			(42,209		)	47,945
Income (Loss) before Income Taxes	22,876			5,678			(29,702		)	63,851
Provision for (Benefit from) Income Taxes	8,603			2,380			(10,824		)	24,660
Net Income (Loss)	$	14,273		$	3,298		$	(18,878	)	$	39,191
Net Income (Loss) Per Common Share, Basic	$	0.30		$	0.07		$	(0.40	)	$	0.83
Net Income (Loss) Per Common Share, Diluted	$	0.30		$	0.07		$	(0.40	)	$	0.83
Weighted Average Common Shares Outstanding, Basic	47,468,569			47,201,954			47,411,054			47,143,430
Weighted Average Common Shares Outstanding, Diluted	47,615,871			47,245,167			47,411,054			47,334,507

See notes to Unaudited Consolidated Financial Statements.

4

BILL BARRETT CORPORATION

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)

(UNAUDITED)

	Three Months Ended June 30,						Six Months Ended June 30,
	2013			2012			2013			2012
	(in thousands)
Net Income (Loss)	$	14,273		$	3,298		$	(18,878	)	$	39,191
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(1,210		)	(12,997		)	(2,502		)	(28,905		)
Other comprehensive loss	(1,210		)	(12,997		)	(2,502		)	(28,905		)
Comprehensive Income (Loss)	$	13,063		$	(9,699	)	$	(21,380	)	$	10,286

See notes to Unaudited Consolidated Financial Statements.

5

BILL BARRETT CORPORATION

CONSOLIDATED STATEMENTS OF CASH FLOWS

(UNAUDITED)

	Six Months Ended June 30,
	2013			2012
	(in thousands)
Operating Activities:
Net Income (Loss)	$	(18,878	)	$	39,191
Adjustments to reconcile to net cash provided by operations:
Depreciation, depletion and amortization	142,745			160,025
Deferred income taxes (benefit)	(10,824		)	24,660
Impairment, dry hole costs and abandonment expense	8,283			21,639
Unrealized derivative gain	(762		)	(69,052		)
Stock compensation and other non-cash charges	9,289			7,640
Amortization of debt discounts and deferred financing costs	3,466			5,002
Gain on sale of properties	(4,193		)	—
Change in operating assets and liabilities:
Accounts receivable	16,506			18,136
Prepayments and other assets	1,585			(6,066		)
Accounts payable, accrued and other liabilities	(23,743		)	(8,853		)
Amounts payable to oil and gas property owners	9,737			(5,383		)
Production taxes payable	(10,182		)	(7,695		)
Net cash provided by operating activities	123,029			179,244
Investing Activities:
Additions to oil and gas properties, including acquisitions	(216,652		)	(460,059		)
Additions of furniture, equipment and other	(1,187		)	(4,241		)
Proceeds from sale of properties and other investing activities	4,086			134
Net cash used in investing activities	(213,753		)	(464,166		)
Financing Activities:
Proceeds from debt	80,000			525,000
Principal payments on debt	(4,501		)	(267,156		)
Proceeds from stock option exercises	3			668
Deferred financing costs and other	(1,348		)	(10,087		)
Net cash provided by financing activities	74,154			248,425
Decrease in Cash and Cash Equivalents	(16,570		)	(36,497		)
Beginning Cash and Cash Equivalents	79,445			57,331
Ending Cash and Cash Equivalents	$	62,875		$	20,834

See notes to Unaudited Consolidated Financial Statements.

6

BILL BARRETT CORPORATION

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY

(UNAUDITED)

(In thousands)

	Common Stock		Additional Paid-In Capital			Retained Earnings			Treasury Stock			Accumulated Other Comprehensive Income			Total Stockholders’ Equity
Balance at December 31, 2011	$	47	$	869,856		$	292,891		$	—		$	56,044		$	1,218,838
Exercise of options, restricted stock activity and shares exchanged for exercise and tax withholding	—		673			—			(2,513		)	—			(1,840		)
APIC pool for excess tax benefits related to share-based compensation	—		32			—			—			—			32
Stock-based compensation	—		16,874			—			—			—			16,874
Retirement of treasury stock	—		(2,513		)	—			2,513			—			—
Settlement of convertible notes	—		(999		)	—			—			—			(999		)
Net income	—		—			582			—			—			582
Effect of derivative financial instruments, net of $30,458 of taxes	—		—			—			—			(50,712		)	(50,712		)
Balance at December 31, 2012	$	47	$	883,923		$	293,473		$	—		$	5,332		$	1,182,775
Exercise of options, restricted stock activity and shares exchanged for exercise and tax withholding	1		2			—			(1,337		)	—			(1,334		)
Stock-based compensation	—		9,761			—			—			—			9,761
Retirement of treasury stock	—		(1,337		)	—			1,337			—			—
Net loss	—		—			(18,878		)	—			—			(18,878		)
Effect of derivative financial instruments, net of $1,503 of taxes	—		—			—			—			(2,502		)	(2,502		)
Balance at June 30, 2013	$	48	$	892,349		$	274,595		$	—		$	2,830		$	1,169,822

See notes to Unaudited Consolidated Financial Statements.

7

BILL BARRETT CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

(UNAUDITED)

June 30, 2013

1. 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.

2. 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 June 30, 2013			As of December 31, 2012
	(in thousands)
Accrued oil, gas and NGL sales	$	61,749		$	69,482
Due from joint interest owners	29,568			36,300
Other	4,163			6,554
Allowance for doubtful accounts	(23		)	(325		)
Total accounts receivable	$	95,457		$	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

8

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 June 30, 2013			As of December 31, 2012
	(in thousands)
Proved properties	$	439,312		$	387,242
Wells and related equipment and facilities	2,830,443			2,625,891
Support equipment and facilities	315,910			304,914
Materials and supplies	15,550			13,220
Total proved oil and gas properties	$	3,601,215		$	3,331,267
Unproved properties	322,364			384,486
Wells and facilities in progress	78,853			72,721
Total unproved oil and gas properties, excluded from amortization	$	401,217		$	457,207
Accumulated depreciation, depletion, amortization and impairment	(1,329,493		)	(1,203,495		)
Total oil and gas properties, net	$	2,672,939		$	2,584,979

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 June 30, 2013, 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:

9

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Non-cash impairment of proved oil and gas properties	$	—	$	—	$	—	$	—
Non-cash impairment of unproved oil and gas properties	—		18,337		—		18,337
Dry hole costs	113		42		964		233
Abandonment expense	1,069		2,696		7,319		3,069
Total non-cash impairment, dry hole costs and abandonment expense	$	1,182	$	21,075	$	8,283	$	21,639

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 June 30, 2013		As of December 31, 2012
	(in thousands)
Accrued drilling, completion and facility costs	$	60,572	$	42,094
Accrued lease operating, gathering, transportation and processing expenses	18,393		16,862
Accrued general and administrative expenses	7,530		13,054
Trade payables and other	34,224		53,007
Total accounts payable and accrued liabilities	$	120,719	$	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 June 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 Per Share. Basic net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding during each period. Diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding and other dilutive securities. Potentially dilutive securities for the diluted net income (loss) 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.

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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 June 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 income (loss) per common share calculation for the three and six months ended June 30, 2013 and 2012. The diluted net income (loss) per common share excludes the anti-dilutive effect of 2,857,757 and 3,771,662 shares of stock options and nonvested performance-based shares of common stock for the three months ended June 30, 2013 and 2012, respectively, and 2,836,480 and 2,896,452 shares of stock options and nonvested performance-based shares of common stock for the six months ended June 30, 2013 and 2012, respectively.

The following table sets forth the calculation of basic and diluted earnings per share:

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013			2012
	(in thousands, except per share amounts)
Net income (loss)	$	14,273	$	3,298	$	(18,878	)	$	39,191
Basic weighted-average common shares outstanding in period	47,469		47,202		47,411			47,143
Add dilutive effects of stock options and nonvested equity shares of common stock	147		43		—			192
Diluted weighted-average common shares outstanding in period	47,616		47,245		47,411			47,335
Basic net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83
Diluted net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83

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 Update 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 FASB 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.

3. Supplemental Disclosures of Cash Flow Information

Supplemental cash flow information is as follows:

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	Six Months Ended June 30,
	2013			2012
	(in thousands)
Cash paid for interest, net of amount capitalized	$	45,709		$	34,656
Cash paid for income taxes	1,861			8
Supplemental disclosures of non-cash investing and financing activities:
Current liabilities	68,731			75,112
Net increase (decrease) in asset retirement obligations	1,888			(545		)
Retirement of treasury stock	(1,337		)	(2,323		)

4. 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 “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 Divestiture proceeds are subject to various purchase price adjustments incurred in the normal course of business and will be finalized during 2013.

5. Long-Term Debt

The Company’s outstanding debt is summarized below:

		As of June 30, 2013							As of December 31, 2012
	Maturity Date	Principal		Unamortized Discount			Carrying Amount		Principal		Unamortized Discount			Carrying Amount
		(in thousands)
Amended Credit Facility (1)	October 31, 2016	$	80,000	$	—		$	80,000	$	—	$	—		$	—
9.875% Senior Notes (2)	July 15, 2016	250,000		(6,348		)	243,652		250,000		(7,209		)	242,791
Convertible Notes (3)	March 15, 2028 (4)	25,344		—			25,344		25,344		—			25,344
7.625% Senior Notes (5)	October 1, 2019	400,000		—			400,000		400,000		—			400,000
7.0% Senior Notes (6)	October 15, 2022	400,000		—			400,000		400,000		—			400,000
Lease Financing Obligation (7)	August 10, 2020	93,095		—			93,095		97,596		—			97,596
Total Debt		$	1,248,439	$	(6,348	)	$	1,242,091	$	1,172,940	$	(7,209	)	$	1,165,731
Less: Current Portion of Long-Term Debt		9,227		—			9,227		9,077		—			9,077
Total Long-Term Debt		$	1,239,212	$	(6,348	)	$	1,232,864	$	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 approximately $263.1 million and $271.9 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013. See Note 13.

(3) The aggregate estimated fair value of the Convertible Notes was approximately $24.7 million and $25.3 million as of June 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 $417.5 million and $435.0 million as of June 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 $400.0 million and $413.8 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

(7) The aggregate estimated fair value of the Lease Financing Obligation was approximately $90.1 million and $97.7 million as of June 30, 2013 and 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.

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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 1.7% for the three months ended June 30, 2013 and 2012, and 1.7% and 1.8% for the six months ended June 30, 2013 and 2012, respectively.

The borrowing base is required to be re-determined twice per year. The borrowing base was re-affirmed at $825.0 million as of April 24, 2013 related to its normal spring re-determination. 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 June 30, 2013, the Company had $80.0 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, effective May 4, 2010, which reduces the current borrowing capacity of the Amended Credit Facility to $719.0 million.

9.875% Senior Notes Due 2016

On July 8, 2009, the Company issued $250.0 million in aggregate principal amount of 9.875% Senior Notes due 2016 at 95.172% of par resulting in a discount of $12.1 million. The 9.875% Senior Notes were scheduled to mature on July 15, 2016. On June 14, 2013, the Company delivered a notice of redemption to the holders of the 9.875% Senior Notes announcing that the Company elected, pursuant to the indenture for the notes, to redeem the entire outstanding $250.0 million principal amount of the notes on July 15, 2013 for a redemption price of 104.938% of the principal amount of the notes. The Company redeemed the 9.875% Senior Notes in full on July 15, 2013. See Note 13 for additional information regarding the redemption of the 9.875% Senior Notes.

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 9.875% Senior Notes, 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, 9.875% Senior 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, the 9.875% Senior 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

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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 beginning October 15, 2012. 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, 9.875% Senior 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, the 9.875% Senior Notes and the 7.625% Senior Notes. The 7.0% Senior Notes include certain covenants that limit the Company’s ability to incur additional indebtedness, make restricted payments, create liens or sell assets and that prohibit the Company from paying dividends. The Company is currently in compliance with all financial covenants and has complied with all financial covenants since issuance.

Lease Financing Obligation Due 2020

On July 23, 2012, the Company entered into a lease financing arrangement with Bank of America Leasing & Capital, LLC as the lead bank (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.

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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Amended Credit Facility (1)
Cash interest	$	1,051	$	1,106	$	1,915	$	2,254
Non-cash interest	$	586	$	586	$	1,171	$	1,171
9.875% Senior Notes (2)
Cash interest	$	6,172	$	6,172	$	12,344	$	12,344
Non-cash interest	$	682	$	636	$	1,361	$	1,253
Convertible Notes (3)
Cash interest	$	320	$	370	$	633	$	2,269
Non-cash interest	$	1	$	1	$	3	$	1,769
7.625% Senior Notes (4)
Cash interest	$	7,625	$	7,625	$	15,250	$	15,250
Non-cash interest	$	263	$	260	$	526	$	541
7.0% Senior Notes (5)
Cash interest	$	7,000	$	7,000	$	14,000	$	8,397
Non-cash interest	$	194	$	201	$	389	$	267
Lease Financing Obligation (6)
Cash interest	$	768	$	—	$	1,555	$	—
Non-cash interest	$	8	$	—	$	16	$	—

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(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. See Note 13.

(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.

6. Asset Retirement Obligations

A reconciliation of the Company’s asset retirement obligations for the six months ended June 30, 2013 is as follows (in thousands):

As of December 31, 2012	$	47,616
Liabilities incurred	1,009
Liabilities settled	(623		)
Disposition of properties	(330		)
Accretion expense	1,707
Revisions to estimate	1,216
As of June 30, 2013	$	50,595
Less: current asset retirement obligations	896
Long-term asset retirement obligations	$	49,699

7. 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

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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 June 30, 2013
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Deferred Compensation Plan	$	824	$	—	$	—	$	824
Cash Equivalents - Money Market Funds	8,562		—		—		8,562
Commodity Derivatives	—		33,172		—		33,172
Liabilities
Commodity Derivatives	$	—	$	3,856	$	—	$	3,856

	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 value of the Company’s fixed rate 9.875% Senior Notes, 7.625% Senior Notes and 7.0% Senior Notes was $1,081.0 million and $1,121.0 million as of June 30, 2013 and December 30, 2012, respectively, and is 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

16

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 $80.0 million as of June 30, 2013 approximates its fair value due to its floating rate structure. The Convertible Notes fair value of $24.7 million and $25.3 million as of June 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 value of $90.1 million and $97.7 million as of June 30, 2013 and December 31, 2012, respectively, is 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 June 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. The inputs used to determine such fair value are primarily based upon internally developed cash flow models and would generally be classified within Level 3. The Company also applied fair value accounting guidance to measure the assets and liabilities in the Divestiture in 2012. 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 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.

8. 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.

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	As of June 30, 2013
Balance Sheet	Gross Amounts of Recognized Assets			Gross Amounts Offset in the Balance Sheet				Net Amounts of Assets Presented in the Balance Sheet
				(in thousands)
Derivative assets	$	22,898		$	(3,317	)	(1)	$	19,581
Deferred financing costs and other noncurrent assets	10,274			(483		)	(1)	9,791			(2)
Total derivative assets	$	33,172		$	(3,800	)		$	29,372
Balance Sheet	Gross Amounts of Recognized Liabilities			Gross Amounts Offset in the Balance Sheet				Net Amounts of Liabilities Presented in the Balance Sheet
				(in thousands)
Derivative liabilities	$	(3,373	)	$	3,317		(3)	$	(56	)
Derivatives and other noncurrent liabilities	(483		)	483			(3)	—
Total derivative liabilities	$	(3,856	)	$	3,800			$	(56	)
	As of December 31, 2012
Balance Sheet	Gross Amounts of Recognized Assets			Gross Amounts Offset in the Balance Sheet				Net Amounts of Assets Presented in the Balance 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
Balance Sheet	Gross Amounts of Recognized Liabilities			Gross Amounts Offset in the Balance Sheet				Net Amounts of Liabilities Presented in the Balance 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 June 30, 2013 and December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $24.1 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 and losses, 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 Cash Flow Hedges	Three Months Ended June 30,				Six Months Ended June 30,
		2013		2012		2013		2012
		(in thousands)
Amount of Gain Reclassified from AOCI into Income (net of tax) (1) (2)	Commodity Hedges	$	1,210	$	12,997	$	2,502	$	28,905

(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 $7.8 million for the three months ended June 30, 2013 and 2012, respectively, and $1.5 million and $17.4 million for the six months ended June 30, 2013 and 2012, respectively.

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

	July –December 2013	For the year 2014	For the  year 2015
Oil (Bbls)	1,527,200	2,205,400	365,000
Natural Gas (MMbtu)	22,855,000	30,415,000	3,650,000
Natural Gas Liquids (Bbls)	160,714	—	—

The table below summarizes the realized and unrealized gains and losses the Company recognized related to its oil, gas and NGL derivative instruments for the periods indicated:

	Three Months Ended June 30,					Six Months Ended June 30,
	2013			2012		2013		2012
	(in thousands)
Realized gains on derivatives designated as cash flow hedges (1)	$	1,936		$	20,798	$	4,003	$	46,263
Realized gains (losses) on derivatives not designated as cash flow hedges	$	(227	)	$	18,916	$	6,226	$	22,719
Unrealized gains on derivatives not designated as cash flow hedges	37,066			28,108		762		69,052
Total commodity derivative gain (2)	$	36,839		$	47,024	$	6,988	$	91,771

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

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

The table below summarizes the realized gains and losses the Company recognized related to its oil, natural gas and NGL derivative instruments by commodity type for the periods indicated:

	Three Months Ended June 30,					Six Months Ended June 30,
	2013			2012		2013		2012
	(in thousands)
Realized gains on derivatives designated as cash flow hedges
Oil	$	512		$	777	$	913	$	1,546
Gas	1,424			20,021		3,090		44,717
Total (1)	$	1,936		$	20,798	$	4,003	$	46,263
Realized gains (losses) on derivatives not designated as cash flow hedges
Oil	$	2,066		$	3,009	$	4,051	$	1,550
Gas	(3,433		)	12,987		609		16,828
NGL	1,140			2,920		1,566		4,341
Total (2)	$	(227	)	$	18,916	$	6,226	$	22,719

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

(2) Included in commodity derivative gain 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 June 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

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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.

9. 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 six months ended June 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 six months ended June 30, 2013.

Income tax expense for the three and six months ended June 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.

10. 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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Common stock options	$	727	$	1,573	$	3,217	$	3,673
Nonvested equity common stock	1,588		1,797		3,988		3,774
Nonvested equity common stock units	312		—		712		—
Nonvested performance-based equity	530		388		698		803
Total	$	3,157	$	3,758	$	8,615	$	8,250

Unrecognized compensation cost as of June 30, 2013 was $22.5 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 2.5 years.

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

20

	Three Months Ended June 30, 2013			Three Months Ended June 30, 2012
	Number of Options	Weighted Average Price Per Share		Number of Options	Weighted Average Price Per Share
Options to purchase shares of common stock	—	$	—	9,576	$	23.47
	Three Months Ended June 30, 2013			Three Months Ended June 30, 2012
	Number of Shares	Weighted Average Grant Date Fair Value Per Share		Number of Shares	Weighted Average Grant Date Fair Value Per Share
Nonvested equity common stock	16,880	$	19.54	24,617	$	23.54
Nonvested equity common stock units	43,824	$	22.38	—	$	—
Nonvested performance-based equity shares	13,007	$	17.26	4,221	$	23.58
Total shares granted	73,711			28,838

	Six Months Ended June 30, 2013			Six Months Ended June 30, 2012
	Number of Options	Weighted Average Price Per Share		Number of Options	Weighted Average Price Per Share
Options to purchase shares of common stock	—	$	—	555,682	$	27.49
	Six Months Ended June 30, 2013			Six Months Ended June 30, 2012
	Number of Shares	Weighted Average Grant Date Fair Value Per Share		Number of Shares	Weighted Average Grant Date Fair Value Per Share
Nonvested equity common stock	557,260	$	17.32	229,114	$	26.67
Nonvested equity common stock units	52,219	$	22.04	—	$	—
Nonvested performance-based equity shares	287,986	$	16.60	176,587	$	27.65
Total shares granted	897,465			405,701

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 six months ended June 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 $0.2 million of non-cash stock-based compensation expense for the six months ended June 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 June 30, 2013 and 2012, respectively, and $0.1 million and $0.4 million of non-cash stock-based compensation expense for the six months ended June 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 were subject to the new grant date on February 27, 2013, and the fair value was remeasured at the grant date. All remaining unvested shares could potentially vest if all performance goals are met at the stretch level. 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

21

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 of non-cash stock-based compensation expense related to these awards during the three months ended June 30, 2013, and $0.2 million for the six months ended June 30, 2013.

In February 2013, the Compensation Committee established vesting terms of the Company’s nonvested equity awards in the 2010 Program that are subject to a market performance-based vesting condition, which is based on the Company’s TSR ranking relative to a defined peer group’s individual TSRs. In February 2013, 22,710 market-based nonvested equity shares of common stock were subject to the new grant date on February 27, 2013, and the fair value was remeasured at the grant date. 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 of non-cash stock-based compensation expense related to these awards for the three months ended June 30, 2013, and $0.05 million for the six months ended June 30, 2013.

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 13,007 and 287,986 shares were granted under this program during the three and six months ended June 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 $0.3 million of non-cash stock-based compensation expense related to these awards for the three months ended June 30, 2013, and $0.4 million for the six months ended June 30, 2013.

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 six months ended June 30, 2013 and 2012 is presented below:

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
Director fees (shares)	3,511		1,657		11,906		3,175
Stock-based compensation (in thousands)	$	71	$	36	$	241	$	75

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 $0.3 million and $0.4 million for the three months ended June 30, 2013 and 2012, respectively, and $1.2 million for both the six months ended June 30, 2013 and 2012.

22

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 $0.8 million and $1.0 million as of June 30, 2013 and December 31, 2012, respectively, of which $0.3 million was classified as current as of both June 30, 2013 and December 31, 2012.

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.

11. 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 June 30, 2013
	(in thousands)
2013	$	6,069
2014	12,139
2015	12,139
2016	12,139
2017	12,139
Thereafter	32,368
Total	$	86,993

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 11 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 $18.0 million of transportation demand charges for the three and six months ended June 30, 2013, respectively. The Company paid $1.4 million and $2.0 million of firm processing charges for the three and six months ended June 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 $11.1 million and $22.3 million of transportation demand charges for the three and six months ended June 30, 2012, respectively. The Company paid $1.6 million and $3.1 million of firm processing charges for the three and six months ended June 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 June 30, 2013
	(in thousands)
2013	$	28,900
2014	57,929
2015	58,065
2016	56,464
2017	51,824
Thereafter	140,726
Total	$	393,908

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Drilling, Lease and Other Commitments. At June 30, 2013, the Company had one drilling commitment through 2014, which requires the Company to drill two wells before October 31, 2014. If the Company does not drill the two wells, it is required to pay a contracted amount of $1.3 million. The Company also 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 $1.0 million for both the three and six months ended June 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 June 30, 2013
	(in thousands)
2013	$	2,118
2014	3,625
2015	2,995
2016	2,519
2017	2,481
Thereafter	3,154
Total	$	16,892

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 financial position, cash flows or results of operations.

12. Guarantor Subsidiaries

In addition to the Amended Credit Facility, 9.875% Senior Notes, 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

24

	As of June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Assets:
Current assets	$	180,787		$	2,437		$	—	$	183,224
Property and equipment, net	2,589,265			108,789			—		2,698,054
Intercompany receivable (payable)	146,236			(146,236		)	—		—
Investment in subsidiaries	(40,663		)	—			40,663		—
Noncurrent assets	33,889			—			—		33,889
Total assets	$	2,909,514		$	(35,010	)	$	40,663	$	2,915,167
Liabilities and Stockholders’ Equity:
Current liabilities	$	201,900		$	845		$	—	$	202,745
Long-term debt	1,232,864			—			—		1,232,864
Deferred income taxes	253,194			2,251			—		255,445
Other noncurrent liabilities	51,734			2,557			—		54,291
Stockholders’ equity	1,169,822			(40,663		)	40,663		1,169,822
Total liabilities and stockholders’ equity	$	2,909,514		$	(35,010	)	$	40,663	$	2,915,167

	As of December 31, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(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 June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	135,631		$	6,668		$	—		$	142,299
Operating expenses	(114,207		)	(4,088		)	—			(118,295		)
General and administrative	(13,273		)	—			—			(13,273		)
Interest income and other income	12,145			—			—			12,145
Income before income taxes and equity in earnings of subsidiaries	20,296			2,580			—			22,876
Provision for income taxes	(8,603		)	—			—			(8,603		)
Equity in earnings of subsidiaries	2,580			—			(2,580		)	—
Net income	$	14,273		$	2,580		$	(2,580	)	$	14,273

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	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	265,771		$	14,805		$	—		$	280,576
Operating expenses	(226,279		)	(7,935		)	—			(234,214		)
General and administrative	(33,855		)	—			—			(33,855		)
Interest income and other income (expense)	(42,209		)	—			—			(42,209		)
Income (loss) before income taxes and equity in earnings of subsidiaries	(36,572		)	6,870			—			(29,702		)
Benefit from income taxes	10,824			—			—			10,824
Equity in earnings of subsidiaries	6,870			—			(6,870		)	—
Net income (loss)	$	(18,878	)	$	6,870		$	(6,870	)	$	(18,878	)

	Three Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	155,587		$	4,765		$	—		$	160,352
Operating expenses	(158,252		)	(4,611		)	—			(162,863		)
General and administrative	(15,036		)	—			—			(15,036		)
Interest and other income	23,225			—			—			23,225
Income before income taxes and equity in earnings of subsidiaries	5,524			154			—			5,678
Provision for income taxes	(2,380		)	—			—			(2,380		)
Equity in earnings of subsidiaries	154			—			(154		)	—
Net income	$	3,298		$	154		$	(154	)	$	3,298

	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	330,121		$	9,407		$	—		$	339,528
Operating expenses	(281,323		)	(8,823		)	—			(290,146		)
General and administrative	(33,476		)	—			—			(33,476		)
Interest and other income	47,945			—			—			47,945
Income before income taxes and equity in earnings of subsidiaries	63,267			584			—			63,851
Provision for income taxes	(24,660		)	—			—			(24,660		)
Equity in earnings of subsidiaries	584			—			(584		)	—
Net income	$	39,191		$	584		$	(584	)	$	39,191

Condensed Consolidating Statements of Comprehensive Income (Loss)

26

	Three Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	14,273		$	2,580	$	(2,580	)	$	14,273
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(1,210		)	—		—			(1,210		)
Other comprehensive loss	(1,210		)	—		—			(1,210		)
Comprehensive income	$	13,063		$	2,580	$	(2,580	)	$	13,063
	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income (loss)	$	(18,878	)	$	6,870	$	(6,870	)	$	(18,878	)
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(2,502		)	—		—			(2,502		)
Other comprehensive loss	(2,502		)	—		—			(2,502		)
Comprehensive income (loss)	$	(21,380	)	$	6,870	$	(6,870	)	$	(21,380	)

	Three Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	3,298		$	154	$	(154	)	$	3,298
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(12,997		)	—		—			(12,997		)
Other comprehensive loss	(12,997		)	—		—			(12,997		)
Comprehensive income (loss)	$	(9,699	)	$	154	$	(154	)	$	(9,699	)
	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	39,191		$	584	$	(584	)	$	39,191
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(28,905		)	—		—			(28,905		)
Other comprehensive loss	(28,905		)	—		—			(28,905		)
Comprehensive income	$	10,286		$	584	$	(584	)	$	10,286

27

Condensed Consolidating Statements of Cash Flows

	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Cash flows from operating activities	$	112,350		$	10,679		$	—	$	123,029
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(203,397		)	(13,255		)	—		(216,652		)
Additions to furniture, fixtures and other	731			(1,918		)	—		(1,187		)
Proceeds from sale of properties and other investing activities	4,086			—			—		4,086
Cash flows from financing activities:
Proceeds from debt	80,000			—			—		80,000
Principal payments on debt	(4,501		)	—			—		(4,501		)
Intercompany transfers	(4,494		)	4,494			—		—
Other financing activities	(1,345		)	—			—		(1,345		)
Change in cash and cash equivalents	(16,570		)	—			—		(16,570		)
Beginning cash and cash equivalents	79,395			50			—		79,445
Ending cash and cash equivalents	$	62,825		$	50		$	—	$	62,875

	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Cash flows from operating activities	$	175,577		$	3,667		$	—	$	179,244
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(451,421		)	(8,638		)	—		(460,059		)
Additions to furniture, fixtures and other	(4,241		)	—			—		(4,241		)
Proceeds from sale of properties and other investing activities	134			—			—		134
Cash flows from financing activities:
Proceeds from debt	525,000			—			—		525,000
Principal payments on debt	(267,156		)	—			—		(267,156		)
Intercompany transfers	(4,971		)	4,971			—		—
Other financing activities	(9,419		)	—			—		(9,419		)
Change in cash and cash equivalents	(36,497		)	—			—		(36,497		)
Beginning cash and cash equivalents	57,281			50			—		57,331
Ending cash and cash equivalents	$	20,784		$	50		$	—	$	20,834

13. Subsequent Events

On June 14, 2013, the Company delivered a notice of redemption to the holders of its 9.875% Senior Notes announcing that, pursuant to the indenture for the notes, the Company elected to redeem the entire outstanding $250.0 million principal amount of the notes on July 15, 2013 for a redemption price of 104.938% of the principal amount of the notes. The Company drew down $280.0 million on its revolving credit facility on July 12, 2013 to fund the redemption of the notes for $262.3 million as well as make the final semi-annual interest payment of $12.3 million. At the redemption date there were unamortized debt discount and deferred financing costs related to the notes resulting in a loss upon settlement of $21.4 million, which will be recorded in the quarter ended September 30, 2013.

28

Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations.

This Quarterly Report on Form 10-Q contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, Section 21E of the Securities Exchange Act of 1934, as amended, and the Private Securities Litigation Reform Act of 1995. Forward-looking statements include statements as to our future plans, estimates, beliefs and expected performance. Forward-looking statements are dependent upon events, risks and uncertainties that may be outside our control. Our actual results could differ materially from those discussed in these forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to, the following risks and uncertainties:

• volatility of market prices received for oil, natural gas and natural gas liquids (“NGLs”);

• costs and availability of third party facilities for gathering, processing, refining and transportation;

• ability to receive drilling and other permits, regulatory approvals and required surface access and rights of way;

• higher than expected costs and expenses including production, drilling and well equipment costs;

• economic and competitive conditions;

• reductions in the borrowing base under our amended revolving bank credit facility (the “Amended Credit Facility”);

• declines in the values of our oil and natural gas properties resulting in impairments;

• changes in estimates of proved reserves;

• compliance with environmental and other regulations;

• derivative and hedging activities;

• potential failure to achieve expected production from existing and future exploration or development projects or acquisitions;

• occurrence of property divestitures or acquisitions;

• legislative or regulatory changes including initiatives related to drilling and completion techniques such as hydraulic fracturing;

• future processing volumes and pipeline throughput;

• the potential for production decline rates from our wells to be greater than we expect;

• ability to replace natural production declines with new drilling or recompletion activities;

• exploration risks such as drilling unsuccessful wells;

• capital expenditures and other contractual obligations;

• debt and equity market conditions;

• liabilities resulting from litigation concerning alleged damages related to environmental issues, pollution, contamination, personal injury, royalties, marketing, title to properties, validity of leases, or other matters that may not be covered by an effective indemnity or insurance;

• the ability to obtain industry partners for our prospects on favorable terms to reduce our capital risks and accelerate our exploration activities;

• changes in tax rates; and

• other uncertainties, as well as those factors discussed below and in our Annual Report on Form 10-K for the year ended December 31, 2012 under the “Cautionary Note Regarding Forward-Looking Statements” and “Risk Factors” sections and in Item 1A, “Risk Factors” of this Quarterly Report on Form 10-Q, all of which are difficult to predict.

In light of these risks, uncertainties and assumptions, the forward-looking events discussed may not occur. Readers should not place undue reliance on these forward-looking statements, which reflect management’s views only as of the date hereof. Other than as required under the securities laws, we do not undertake any obligation to publicly correct or update any forward-looking statements whether as a result of changes in internal estimates or expectations, new information, subsequent events or circumstances or otherwise.

Overview

Bill Barrett Corporation together with our wholly-owned subsidiaries (“the Company”, “we”, “our” or “us”) develops oil, natural gas and NGLs in the Rocky Mountain region of the United States. We seek to build stockholder value through profitable growth in cash flow, reserves and production through the development of our oil, natural gas and NGL assets. Due to the decline in natural gas prices resulting from the increased supply over the past few years, we have shifted our focus to finding, acquiring and developing oil resources. Therefore, we will see a decrease in gas production due to suspended gas drilling. We seek high quality development projects with the potential to provide long-term drilling inventories that generate high returns. Substantially all of our revenues are generated through the sale of oil and natural gas production and NGLs recovery at market prices.

29

We were formed in January 2002 and are incorporated in the State of Delaware. In December 2004, we completed our initial public offering of 14,950,000 shares of our common stock at a price to the public of $25.00 per share. Since inception, we have built our portfolio of properties primarily through acquisitions where we seek to add value through our geologic and operational expertise. Our acquisitions have included key assets in the Piceance (Colorado), Uinta (Utah), Denver-Julesburg (Colorado and Wyoming) and Powder River (Wyoming) Basins in the Rocky Mountain region (the “Rockies”). We also may sell properties when the opportunity arises or when business conditions warrant, as demonstrated by the sale of our Wind River Basin and Powder River Basin properties and a portion of our Piceance Basin properties in December 2012.

We are committed to developing and producing oil, natural gas and NGLs in a responsible and safe manner. We work diligently with environmental, wildlife and community organizations to ensure that our exploration and development activities are designed with all stakeholders in mind.

We operate in one industry segment, which is the development and production of crude oil, natural gas and NGLs, and all of our operations are conducted in the United States. Consequently, we currently report a single reportable segment.

Results of Operations

The following table sets forth selected operating data for the periods indicated:

30

Three Months Ended June 30, 2013 Compared with Three Months Ended June 30, 2012

	Three Months Ended June 30,				Increase (Decrease)
	2013		2012		Amount			Percent
	($ in thousands, except per unit data)
Operating Results:
Operating and Other Revenues
Oil, gas and NGL production	$	140,380	$	159,490	$	(19,110	)	(12	)%
Other	1,919		862		1,057			123	%
Operating Expenses
Lease operating expense	16,112		19,030		(2,918		)	(15	)%
Gathering, transportation and processing expense	18,772		25,862		(7,090		)	(27	)%
Production tax expense	7,781		6,892		889			13	%
Exploration expense	141		4,062		(3,921		)	(97	)%
Impairment, dry hole costs and abandonment expense	1,182		21,075		(19,893		)	(94	)%
Depreciation, depletion and amortization	74,307		85,942		(11,635		)	(14	)%
General and administrative expense (1)	10,047		11,314		(1,267		)	(11	)%
Non-cash stock-based compensation expense (1)	3,226		3,722		(496		)	(13	)%
Total operating expenses	$	131,568	$	177,899	$	(46,331	)	(26	)%
Production Data (2):
Natural gas (MMcf)	14,314		26,094		(11,780		)	(45	)%
Oil (MBbls)	825		634		191			30	%
NGLs (MBbls)	351		—		351			*nm
Combined volumes (MMcfe)	21,370		29,898		(8,528		)	(29	)%
Daily combined volumes (MMcfe/d)	235		329		(94		)	(29	)%
Average Realized Prices (3):
Natural gas (per Mcf) (4)	$	3.92	$	4.77	$	(0.85	)	(18	)%
Oil (per Bbl)	82.11		84.86		(2.75		)	(3	)%
NGLs (per Bbl)	46.38		—		46.38			*nm
Combined (per Mcfe)	6.56		5.97		0.59			10	%
Average Costs (per Mcfe):
Lease operating expense	$	0.75	$	0.64	$	0.11		17	%
Gathering, transportation and processing expense	0.88		0.87		0.01			1	%
Production tax expense	0.36		0.23		0.13			57	%
Depreciation, depletion and amortization	3.48		2.87		0.61			21	%
General and administrative expense (5)	0.47		0.38		0.09			24	%

* Not meaningful.

(1) Non-cash stock-based compensation expense is presented herein as a separate line item but is combined with general and administrative expense for a total of $13.3 million and $15.0 million for the three months ended June 30, 2013 and 2012, respectively, in the Unaudited Consolidated Statements of Operations. This separate presentation is a non-GAAP measure. Management believes the separate presentation of the non-cash component of general and administrative expense is useful because the cash portion provides a better understanding of our required cash for general and administrative expenses. We also believe that this disclosure allows for a more accurate comparison to our peers, which may have higher or lower expenses associated with stock-based grants.

(2) Prior to 2013, NGL volumes were included within natural gas production data, which impacts the comparability for the two periods presented.

(3) Average realized prices shown in the table are net of the effects of all realized commodity hedging transactions.

(4) Natural gas prices for 2012 include the effect of NGL related revenue.

(5) Excludes non-cash stock-based compensation expense as described in Note 1 above. This presentation is a non-GAAP measure. Average costs per Mcfe for general and administrative expense, including non-cash stock-based compensation

31

expense, as presented in the Unaudited Consolidated Statements of Operations, were $0.62 and $0.50 for the three months ended June 30, 2013 and 2012, respectively.

Production Revenues and Volumes. Historically, we have reported our natural gas production as a single stream of wet gas measured at the well head. Beginning in the first quarter of 2013, we changed our reporting for natural gas volumes to show natural gas and NGL production volumes consistent with title transfer for each product. Effective January 1, 2013, substantially all of our gas processing contracts were amended to designate title transfer of gas and NGLs processed at the tailgate of each processing plant.

Production revenues decreased to $140.4 million for the three months ended June 30, 2013 from $159.5 million for the three months ended June 30, 2012. This decrease is primarily due to a 29%decrease in production volumes. The decrease in production reduced production revenues by approximately $56.0 million, while the increase in average prices increased production revenues by approximately $36.9 million.

We discontinued hedge accounting as of January 1, 2012. All accumulated gains or losses related to the discontinued cash flow hedges were recorded in accumulated other comprehensive income (“AOCI”) as of January 1, 2012 and will remain in AOCI until the underlying transaction occurs. As the underlying transaction occurs, these gains or losses are reclassified from AOCI into oil, gas and NGL production revenues. The amount reclassified to oil, gas and NGL production revenues was a gain of $1.9 million and $20.8 million for the three months ended June 30, 2013 and 2012, respectively.

Total production volumes of 21.4 Bcfe for the three months ended June 30, 2013decreased from 29.9 Bcfe for the three months ended June 30, 2012. We completed a sale of natural gas assets on December 31, 2012, including 100% of our Wind River Basin and Powder River Basin coalbed methane properties (“PRB-CBM”) and an initial 18% interest in the Gibson Gulch assets in the Piceance Basin that progresses to a 26% interest in 2016 (the "December 2012 Sale"). Lower natural gas commodity prices caused us to discontinue drilling activity in the Piceance Basin and West Tavaputs area in the Uinta Basin in 2012 to concentrate on our oil development programs, which has continued to impact 2013 gas production volumes. These decreases were partially offset by a 30% overall increase in oil production with increases in the Uinta Oil Program, DJ Basin and Powder River Oil Program, offset by a decrease in the Piceance Basin oil production, for the three months ended June 30, 2013. Additional information concerning production is in the following table:

	Three Months Ended June 30, 2013				Three Months Ended June 30, 2012				% Increase (Decrease)
	Oil	NGL(2)	Natural Gas(2)	Total	Oil	NGL(2)	Natural Gas(2)	Total	Oil	NGL(2)	Natural Gas(2)	Total
	(MBbls)	(MBbls)	(MMcf)	(MMcfe)	(MBbls)	(MBbls)	(MMcf)	(MMcfe)	(MBbls)	(MBbls)	(MMcf)	(MMcfe)
Piceance Basin	82	269	6,883	8,989	162	—	12,251	13,223	(49)%	*nm	(44)%	(32)%
Uinta- West Tavaputs	9	—	6,156	6,210	18	—	9,114	9,222	(50)%	*nm	(32)%	(33)%
Uinta Oil Program	459	35	717	3,681	327	—	582	2,544	40%	*nm	23%	45%
DJ Basin	149	45	452	1,616	96	—	248	824	55%	*nm	82%	96%
Powder River Oil	126	2	52	820	25	—	20	170	404%	*nm	160%	382%
Other (1)	—	—	54	54	6	—	3,879	3,915	(100)%	*nm	(99)%	(99)%
Total	825	351	14,314	21,370	634	—	26,094	29,898	30%	*nm	(45)%	(29)%

* Not meaningful.

(1) Other includes PRB–CBM natural gas volumes of 2,788 MMcf for 2012 and Wind River natural gas production volumes of 1,041 MMcf and oil production of 5 MBbls for 2012.

(2) Prior to 2013, NGL volumes were included in natural gas production data, which impacts the comparability for the two periods presented.

Hedging Activities. During the three months ended June 30, 2013, approximately 83% of our oil volumes, 84% of our natural gas volumes and 23% of our NGL related volumes were subject to financial hedges, which resulted in increases in oil revenues of $2.6 million and NGL revenues of $1.1 million, offset by a decrease in natural gas revenues of $2.0 million after settlements for all commodity derivatives. Of the $1.7 million total settlements for the three months ended June 30, 2013, a gain of $1.9 million was included in oil, gas and NGL production revenues and a loss of $0.2 million was included in commodity derivative gain in the Unaudited Statements of Operations. During the three months ended June 30, 2012, approximately 76% of our oil volumes, 66% of our natural gas volumes (excluding basis only swaps, which were equivalent to

32

7% of our natural gas volumes), and 26% of our NGL related volumes were subject to financial hedges, which resulted in a decrease in oil revenues of $3.8 million and an increase in natural gas revenues of $35.9 million after settlements for all commodity derivatives, including basis only and NGL swaps. Of the $39.7 million total settlements for the three months ended June 30, 2012, $20.8 million was included in oil, gas and NGL production revenues and $18.9 million was included in commodity derivative gain in the Unaudited Statements of Operations. We may not always be able to generate increases in revenues based on hedge settlements due to the volatility of prices for oil, natural gas and NGLs and current market conditions.

Other Operating Revenues. Other operating revenues increased to $1.9 million for the three months ended June 30, 2013 from $0.9 million for the three months ended June 30, 2012. Other operating revenues for the three months ended June 30, 2013 primarily consisted of $0.7 million in net gains realized from the sale of properties and $1.2 million of income from gathering and compression fees received from third parties. Other operating revenues for the three months ended June 30, 2012 consisted of $0.9 million of income from gathering, compression and salt-water disposal fees received from third parties.

Lease Operating Expense. Lease operating expense (“LOE”) increased to $0.75 per Mcfe for the three months ended June 30, 2013 from $0.64 per Mcfe for the three months ended June 30, 2012. LOE on a per Mcfe basis is inherently higher for our oil producing properties such as those in our Uinta Oil and DJ Basin development areas. In addition, the December 2012 Sale consisted of natural gas properties in the Wind River and Powder River Basins, which were lower LOE per Mcfe properties, contributing to higher LOE per Mcfe unit cost.

Gathering, Transportation and Processing Expense. Gathering, transportation and processing (“GTP”) expense per Mcfe was consistent for both the three months ended June 30, 2013 and 2012. GTP expense was $0.88 per Mcfe for the three months ended June 30, 2013 and $0.87 per Mcfe for the three months ended June 30, 2012.

Production Tax Expense. Total production taxes increased to $7.8 million for the three months ended June 30, 2013 from $6.9 million for the three months ended June 30, 2012. Production taxes are primarily based on the wellhead values of production, which excludes gains and losses associated with hedging activities. Production taxes as a percentage of oil, natural gas and NGL sales before hedging adjustments were 5.6% and 5.0% for the three months ended June 30, 2013 and June 30, 2012, respectively.

Production tax rates vary across the different areas in which we operate. As the proportion of our production changes from area to area, our average production tax rate will vary depending on the quantities produced from each area and the production tax rates in effect for those areas. The increase in the overall production tax rate is consistent with our production increase in states with higher production tax rates.

Exploration Expense. Exploration expense decreased to $0.1 million for the three months ended June 30, 2013 from $4.1 million for the three months ended June 30, 2012. Exploration expense for the three months ended June 30, 2013 consisted of $0.1 million for delay rentals across all basins. Exploration expense for the three months ended June 30, 2012 consisted of $3.7 million of geological and geophysical seismic programs and $0.4 million for delay rentals across all basins.

Impairment, Dry Hole Costs and Abandonment Expense. Our impairment, dry hole costs and abandonment expense decreased to $1.2 million for the three months ended June 30, 2013 from $21.1 million for the three months ended June 30, 2012. For the three months ended June 30, 2013, abandonment expense was $1.1 million and dry hole costs were $0.1 million. For the three months ended June 30, 2012, impairment expense was $18.3 million, abandonment expense associated with exploratory drilling locations was $2.7 million and dry hole costs were $0.1 million. The $18.3 million of impairment related to impairing certain unproved oil and gas properties within various exploration and development projects primarily as a result of unfavorable market conditions or no future plans to evaluate the remaining acreage.

The Company is currently marketing certain non-core unevaluated oil and gas properties. Our marketing efforts may lead to an outright sale of these non-core properties or some other combination of partial sale and drilling obligations to us.  While management believes the fair value of such properties exceeds the carrying value, the fair value received from our marketing efforts regarding these properties may not be greater than or equal to the current carrying value of such properties. If this occurs, we may record a non-cash loss on sale or a non-cash impairment charge to earnings.  This could have a material impact on the reported results of operations in the period any such loss on sale or impairment charge is taken.

Depreciation, Depletion and Amortization. Depreciation, depletion and amortization (“DD&A”) decreased to $74.3 million for the three months ended June 30, 2013 compared with $85.9 million for the three months ended June 30, 2012. The decrease of $11.6 million was a result of the 29%decrease in production for the three months ended June 30, 2013 compared with the three months ended June 30, 2012 offset by an increase in the DD&A rate. The decrease in production accounted for a $24.5 million decrease in DD&A expense, while the overall increase in the DD&A rate accounted for $12.9 million of additional DD&A expense. The increase in the DD&A rate during the three months ended June 30, 2013 was due to an increase

33

in the mix of oil projects, which have higher capital costs compared to natural gas projects compared with the three months ended June 30, 2012.

Under successful efforts accounting, depletion expense is calculated on a field-by-field basis based on geologic and reservoir delineation using the unit-of-production method. The capital expenditures for proved properties for each field compared to the proved reserves corresponding to each producing field determine a depletion rate for current production. For the three months ended June 30, 2013, the relationship of capital expenditures, proved reserves and production from certain producing fields yielded a depletion rate of $3.48 per Mcfe compared with $2.87 per Mcfe for the three months ended June 30, 2012. Future depletion rates will be adjusted to reflect capital expenditures, proved reserve changes and well performance.

General and Administrative Expense. General and administrative expense, excluding non-cash stock-based compensation, decreased to $10.0 million for the three months ended June 30, 2013 from $11.3 million for the three months ended June 30, 2012. General and administrative expense, excluding non-cash stock-based compensation, is a non-GAAP measure. See Note 1 to the table on page 31 for a reconciliation and explanation. On a per Mcfe basis, general and administrative expense, excluding non-cash stock-based compensation, increased to $0.47 per Mcfe for the three months ended June 30, 2013 from $0.38 per Mcfe for the three months ended June 30, 2012, due to the 29%decrease in production as the result of the December 2012 Sale.

Non-cash charges for stock-based compensation for the three months ended June 30, 2013 and 2012 were $3.2 million and $3.7 million, respectively. Non-cash stock-based compensation expense for each of the three months ended June 30, 2013 and 2012 related primarily to vesting of our stock option awards and nonvested shares of common stock issued to employees.

The components of non-cash stock-based compensation for the three months ended June 30, 2013 and 2012 are shown in the following table:

	Three Months Ended June 30,
	2013		2012
	(in thousands)
Stock options and nonvested equity shares of common stock	$	3,026	$	3,539
Shares issued for 401(k) plan	129		147
Shares issued for directors’ fees	71		36
Total	$	3,226	$	3,722

Interest Expense. Interest expense increased to $24.7 million for the three months ended June 30, 2013 from $23.9 million for the three months ended June 30, 2012. The increase for the three months ended June 30, 2013 was primarily due to higher average outstanding borrowings, offset by a slightly lower weighted average interest rate. Our weighted average interest rate for the three months ended June 30, 2013 was 8.1% compared with 8.8% for the three months ended June 30, 2012.

Commodity Derivative Gain.Commodity derivative gaindecreased to $36.8 million for the three months ended June 30, 2013 compared with $47.0 million for the three months ended June 30, 2012 primarily due to the decrease in realized gains from natural gas contracts resulting from an increase in gas commodity pricing for the three months ended June 30, 2013 compared with June 30, 2012, as well as an overall increase in the price of our more recently added hedge positions.

The table below summarizes the realized and unrealized gains and losses we recognized in commodity derivative gain for the periods indicated:

	Three Months Ended June 30,
	2013			2012
	(in thousands)
Realized gain (loss) on derivatives not designated as cash flow hedges	$	(227	)	$	18,916
Unrealized gain on derivatives not designated as cash flow hedges	37,066			28,108
Total commodity derivative gain	$	36,839		$	47,024

Income Tax Expense. Income tax expense totaled $8.6 million for the three months ended June 30, 2013 compared with $2.4 million for the three months ended June 30, 2012, resulting in effective tax rates of 37.6% and 41.9%, respectively. The increase in income tax expense was primarily the result of the variations in revenue and expense components as discussed above and the resulting increase in income before income taxes. The effective tax rate change was primarily the result of a statutory rate increase in 2012, the effect of which was included in income tax expense for the three months ended June 30, 2012, thus increasing the overall effective tax rate. A similar rate change effect did not occur for the three months ended June 30, 2013. For both the 2013 and 2012 periods, our effective tax rate differs from the federal statutory rate primarily as a result

34

of recording stock-based compensation expense and other operating expenses that are not deductible for income tax purposes as well as the effect of state income taxes.

Six Months Ended June 30, 2013 Compared with Six Months Ended June 30, 2012

	Six Months Ended June 30,				Increase (Decrease)
	2013		2012		Amount			Percent
	($ in thousands, except per unit data)
Operating Results:
Operating and Other Revenues
Oil, gas and NGL production	$	274,785	$	336,532	$	(61,747	)	(18	)%
Other	5,791		2,996		2,795			93	%
Operating Expenses
Lease operating expense	34,858		37,668		(2,810		)	(7	)%
Gathering, transportation and processing expense	34,360		53,214		(18,854		)	(35	)%
Production tax expense	13,732		13,099		633			5	%
Exploration expense	236		4,501		(4,265		)	(95	)%
Impairment, dry hole costs and abandonment expense	8,283		21,639		(13,356		)	(62	)%
Depreciation, depletion and amortization	142,745		160,025		(17,280		)	(11	)%
General and administrative expense (1)	25,195		25,114		81			—	%
Non-cash stock-based compensation expense (1)	8,660		8,362		298			4	%
Total operating expenses	$	268,069	$	323,622	$	(55,553	)	(17	)%
Production Data (2):
Natural gas (MMcf)	28,976		51,412		(22,436		)	(44	)%
Oil (MBbls)	1,619		1,115		504			45	%
NGLs (MBbls)	652		—		652			*nm
Combined volumes (MMcfe)	42,602		58,102		(15,500		)	(27	)%
Daily combined volumes (MMcfe/d)	235		319		(84		)	(27	)%
Average Realized Prices (3):
Natural gas (per Mcf) (4)	$	4.01	$	5.11	$	(1.10	)	(22	)%
Oil (per Bbl)	81.93		86.39		(4.46		)	(5	)%
NGLs (per Bbl)	47.27		—		47.27			*nm
Combined (per Mcfe)	6.57		6.18		0.39			6	%
Average Costs (per Mcfe):
Lease operating expense	$	0.82	$	0.65	$	0.17		26	%
Gathering, transportation and processing expense	0.81		0.92		(0.11		)	(12	)%
Production tax expense	0.32		0.23		0.09			39	%
Depreciation, depletion and amortization	3.35		2.75		0.60			22	%
General and administrative expense (5)	0.59		0.43		0.16			37	%

* Not meaningful.

(1) Non-cash stock-based compensation expense is presented herein as a separate line item but is combined with general and administrative expense for a total of $33.9 million and $33.5 million for the six months ended June 30, 2013 and 2012, respectively, in the Unaudited Consolidated Statements of Operations. This separate presentation is a non-GAAP measure. Management believes the separate presentation of the non-cash component of general and administrative expense is useful because the cash portion provides a better understanding of our required cash for general and administrative expenses. We also believe that this disclosure allows for a more accurate comparison to our peers, which may have higher or lower expenses associated with stock-based grants.

35

(2) Prior to 2013, NGL volumes were included within natural gas production data, which impacts the comparability for the two periods presented.

(3) Average realized prices shown in the table are net of the effects of all realized commodity hedging transactions.

(4) Natural gas prices for 2012 include the effect of NGL related revenue.

(5) Excludes non-cash stock-based compensation expense as described in Note 1 above. This presentation is a non-GAAP measure. Average costs per Mcfe for general and administrative expense, including non-cash stock-based compensation expense, as presented in the Unaudited Consolidated Statements of Operations, were $0.79 and $0.58 for the six months ended June 30, 2013 and 2012, respectively.

Production Revenues and Volumes. Production revenues decreased to $274.8 million for the six months ended June 30, 2013 from $336.5 million for the six months ended June 30, 2012. This decrease is primarily due to a 27%decrease in production volumes. The decrease in production reduced production revenues by approximately $99.9 million, while the increase in average prices increased production revenues by approximately $38.2 million.

We discontinued hedge accounting as of January 1, 2012. All accumulated gains or losses related to the discontinued cash flow hedges were recorded in AOCI as of January 1, 2012 and will remain in AOCI until the underlying transaction occurs. As the underlying transaction occurs, these gains or losses are reclassified from AOCI into oil, gas and NGL production revenues. The amount reclassified to oil, gas and NGL production revenues was a gain of $4.0 million and $46.3 million for the six months ended June 30, 2013 and 2012, respectively.

Total production volumes of 42.6 Bcfe for the six months ended June 30, 2013decreased from 58.1 Bcfe for the six months ended June 30, 2012. We completed a sale of natural gas assets on December 31, 2012, including 100% of our Wind River Basin and Powder River Basin coalbed methane properties (“PRB-CBM”) and an initial 18% interest in the Gibson Gulch assets in the Piceance Basin that progresses to a 26% interest in 2016. Lower natural gas commodity prices caused us to discontinue drilling activity in the Piceance Basin and West Tavaputs area in the Uinta Basin in 2012 to concentrate on our oil development programs, which has continued to impact 2013 gas production volumes. These decreases were partially offset by a 45% overall increase in oil production with increases in the Uinta Oil Program, DJ Basin and Powder River Oil Program for the six months ended June 30, 2013. Additional information concerning production is in the following table:

	Six Months Ended June 30, 2013				Six Months Ended June 30, 2012				% Increase (Decrease)
	Oil	NGL(2)	Natural Gas(2)	Total	Oil	NGL(2)	Natural Gas(2)	Total	Oil	NGL(2)	Natural Gas(2)	Total
	(MBbls)	(MBbls)	(MMcf)	(MMcfe)	(MBbls)	(MBbls)	(MMcf)	(MMcfe)	(MBbls)	(MBbls)	(MMcf)	(MMcfe)
Piceance Basin	175	515	13,916	18,056	300	—	23,678	25,478	(42)%	*nm	(41)%	(29)%
Uinta- West Tavaputs	24	—	12,611	12,755	33	—	18,128	18,326	(27)%	*nm	(30)%	(30)%
Uinta Oil Program	936	62	1,442	7,430	592	—	1,095	4,647	58%	*nm	32%	60%
DJ Basin	305	73	811	3,079	144	—	499	1,363	112%	*nm	63%	126%
Powder River Oil	175	2	102	1,164	34	—	61	265	415%	*nm	67%	339%
Other (1)	4	—	94	118	12	—	7,951	8,023	(67)%	*nm	(99)%	(99)%
Total	1,619	652	28,976	42,602	1,115	—	51,412	58,102	45%	*nm	(44)%	(27)%

* Not meaningful.

(1) Other includes PRB–CBM natural gas volumes of 5,796 MMcf for 2012 and Wind River natural gas production volumes of 2,103 MMcf and oil production of 8 MBbls for 2012.

(2) Prior to 2013, NGL volumes were included in natural gas production data, which impacts the comparability for the two periods presented.

Hedging Activities. During the six months ended June 30, 2013, approximately 82% of our oil volumes, 88% of our natural gas volumes and 25% of our NGL related volumes were subject to financial hedges, which resulted in increases in oil revenues of $5.0 million, natural gas revenues of $3.7 million and NGL revenues of $1.5 million after settlements for all commodity derivatives. Of the $10.2 million total settlements for the six months ended June 30, 2013, $4.0 million was included in oil, gas and NGL production revenues and $6.2 million was included in commodity derivative gain in the Unaudited Statements of Operations. During the six months ended June 30, 2012, approximately 82% of our oil volumes, 65% of our natural gas volumes (excluding basis only swaps, which were equivalent to 7% of our natural gas volumes), and 29% of our NGL related volumes were subject to financial hedges, which resulted in a increases in oil revenues of $3.1 million and

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natural gas revenues of $65.9 million after settlements for all commodity derivatives. Of the $69.0 million total settlements for the six months ended June 30, 2012, $46.3 million was included in oil, gas and NGL production revenues and $22.7 million was included in commodity derivative gain in the Unaudited Statements of Operations. We may not always be able to generate increases in revenue based on hedge settlements due to the volatility of prices for oil, natural gas and NGLs and current market conditions.

Other Operating Revenues. Other operating revenues increased to $5.8 million for the six months ended June 30, 2013 from $3.0 million for the six months ended June 30, 2012. Other operating revenues for the six months ended June 30, 2013 primarily consisted of $4.2 million in net gains realized from the sale of properties and $1.6 million of income from gathering and compression fees received from third parties. Other operating revenues for the six months ended June 30, 2012 consisted of $3.0 million of income from gathering, compression and salt-water disposal fees received from third parties.

Lease Operating Expense. LOE increased to $0.82 per Mcfe for the six months ended June 30, 2013 from $0.65 per Mcfe for the six months ended June 30, 2012. In November 2012, a breach and fire occurred on one of our gathering pipelines adjacent to our Dry Canyon compressor station in the West Tavaputs area of the Uinta Basin, damaging ten compressors on location as well as other equipment (the "Dry Canyon Fire"). The increase in LOE on a per Mcfe basis was due to a one-time charge of $1.2 million during the three months ended March 31, 2013 related to testing and reclamation of pipelines as a result of the Dry Canyon Fire. In addition, LOE on a per Mcfe basis is inherently higher for our oil producing properties such as those in our Uinta Oil and DJ Basin development areas. The sale of natural gas properties in the Wind River and Powder River Basins as of December 31, 2012, which were lower LOE per Mcfe properties, also contributed to a higher LOE per Mcfe unit cost.

Gathering, Transportation and Processing Expense. GTP expense decreased to $0.81 per Mcfe for the six months ended June 30, 2013 from $0.92 per Mcfe for the six months ended June 30, 2012. GTP expense for the six months ended June 30, 2013 decreased due to a change in reporting an oil transportation deduction related to certain production within the Uinta Oil Program as a charge against production revenues as of January 1, 2013. These costs were previously included within GTP. The effect on the average per unit oil price is approximately $2.00 per barrel, which reduces GTP by approximately $0.08 per Mcfe for the six months ended June 30, 2013. In addition, GTP expense decreased as a result of a decrease in gathering and processing fees in the West Tavaputs area of the Uinta Basin related to the Dry Canyon Fire. As a result of the Dry Canyon Fire, we exercised the force majeure provision related to certain firm gathering and processing commitments, which negated our minimum volume commitment for firm processing and gathering fees starting from November 2012 through February 28, 2013, and decreased our gathering and processing expense for the six months ended June 30, 2013 by approximately $0.03 per Mcfe.

Production Tax Expense. Total production taxes increased to $13.7 million for the six months ended June 30, 2013 from $13.1 million for the six months ended June 30, 2012. Production taxes are primarily based on the wellhead values of production, which exclude gains and losses associated with hedging activities. Production taxes as a percentage of oil, natural gas and NGL sales before hedging adjustments was 5.1% and 4.5% for the six months ended June 30, 2013 and 2012, respectively.

Production tax rates vary across the different areas in which we operate. As the proportion of our production changes from area to area, our average production tax rate will vary depending on the quantities produced from each area and the production tax rates in effect for those areas. The increase in the overall production tax rate is consistent with our production increase in states with higher production tax rates.

Exploration Expense. Exploration expense decreased to $0.2 million for the six months ended June 30, 2013 from $4.5 million for the six months ended June 30, 2012. Exploration expense for the six months ended June 30, 2013 consisted of $0.1 million of geological and geophysical seismic programs and $0.1 for delay rentals across all basins. Exploration expense for the six months ended June 30, 2012 consisted of $3.9 million of geological and geophysical seismic programs and $0.6 million for delay rentals across all basins.

Impairment, Dry Hole Costs and Abandonment Expense. Our impairment, dry hole costs and abandonment expense decreased to $8.3 million for the six months ended June 30, 2013 from $21.6 million for the six months ended June 30, 2012. For the six months ended June 30, 2013, abandonment expense was $7.3 million associated with exploratory drilling locations and dry hole costs were $1.0 million. For the six months ended June 30, 2012, impairment expense was $18.3 million, abandonment expense associated with exploratory drilling locations was $3.1 million and dry hole costs were $0.2 million. The $18.3 million of impairment expense related to impairing certain unproved oil and gas properties within various exploration and development projects primarily as a result of unfavorable market conditions or no future plans to evaluate the remaining acreage.

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The Company is currently marketing certain non-core unevaluated oil and gas properties. Our marketing efforts may lead to an outright sale of these non-core properties or some other combination of partial sale and drilling obligations to us.  While management believes the fair value of such properties exceeds the carrying value, the fair value received from our marketing efforts regarding these properties may not be greater than or equal to the current carrying value of such properties. If this occurs, we may record a non-cash loss on sale or a non-cash impairment charge to earnings.  This could have a material impact on the reported results of operations in the period any such loss on sale or impairment charge is taken.

Depreciation, Depletion and Amortization. DD&A decreased to $142.7 million for the six months ended June 30, 2013 compared with $160.0 million for the six months ended June 30, 2012. The decrease of $17.3 million was a result of the 27%decrease in production for the six months ended June 30, 2013 compared with the six months ended June 30, 2012 offset by an increase in the DD&A rate. The decrease in production accounted for an $42.6 million decrease in DD&A expense, while the overall increase in the DD&A rate accounted for $25.3 million of additional DD&A expense. The increase in the DD&A rate during the six months ended June 30, 2013 compared with the six months ended June 30, 2012 was due to an increase in the mix of oil projects, which have higher capital costs compared to natural gas projects.

Under successful efforts accounting, depletion expense is calculated on a field-by-field basis based on geologic and reservoir delineation using the unit-of-production method. The capital expenditures for proved properties for each field compared to the proved reserves corresponding to each producing field determine a depletion rate for current production. For the six months ended June 30, 2013, the relationship of capital expenditures, proved reserves and production from certain producing fields yielded a depletion rate of $3.35 per Mcfe compared with $2.75 per Mcfe for the six months ended June 30, 2012. Future depletion rates will be adjusted to reflect capital expenditures, proved reserve changes and well performance.

General and Administrative Expense. General and administrative expense, excluding non-cash stock-based compensation, increased to $25.2 million for the six months ended June 30, 2013 from $25.1 million for the six months ended June 30, 2012. The six months ended June 30, 2013 included one-time executive and other employees' severance expense of approximately $2.6 million. General and administrative expense, excluding non-cash stock-based compensation, is a non-GAAP measure. See Note 1 to the table on page 35 for a reconciliation and explanation. On a per Mcfe basis, general and administrative expense, excluding non-cash stock-based compensation, increased to $0.59 per Mcfe for the six months ended June 30, 2013 from $0.43 per Mcfe for the six months ended June 30, 2012, largely due to the 27%decrease in production as the result of the December 2012 Sale.

Non-cash charges for stock-based compensation for the six months ended June 30, 2013 and the six months ended June 30, 2012 were $8.7 million and $8.4 million, respectively. Non-cash stock-based compensation expense for each of the six months ended June 30, 2013 and 2012 related primarily to vesting of our stock option awards and nonvested shares of common stock issued to employees.

The components of non-cash stock-based compensation for the six months ended June 30, 2013 and 2012 are shown in the following table:

	Six Months Ended June 30,
	2013		2012
	(in thousands)
Stock options and nonvested equity shares of common stock	$	7,963	$	7,829
Shares issued for 401(k) plan	456		458
Shares issued for directors’ fees	241		75
Total	$	8,660	$	8,362

Interest Expense. Interest expense increased to $49.3 million for the six months ended June 30, 2013 from $45.5 million for the six months ended June 30, 2012. The increase for the six months ended June 30, 2013 was primarily due to higher average outstanding borrowings, offset by a lower weighted average interest rate. Our weighted average interest rate for the six months ended June 30, 2013 was 8.2% compared to 9.0% for the six months ended June 30, 2012.

Commodity Derivative Gain.Commodity derivative gaindecreased to $7.0 million for the six months ended June 30, 2013 compared with $91.8 million for the six months ended June 30, 2012 primarily due to the decrease in unrealized gains from natural gas contracts resulting from an increase in future gas commodity pricing as of June 30, 2013 compared with June 30, 2012, as well as an overall increase in the price of our more recently added hedge positions.

The table below summarizes the realized and unrealized gains and losses we recognized in commodity derivative gain for the periods indicated:

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	Six Months Ended June 30,
	2013		2012
	(in thousands)
Realized gain on derivatives not designated as cash flow hedges	$	6,226	$	22,719
Unrealized gain on derivatives not designated as cash flow hedges	762		69,052
Total commodity derivative gain	$	6,988	$	91,771

Income Tax Benefit (Expense). Income tax benefit totaled $10.8 million for the six months ended June 30, 2013 compared to an expense of $24.7 million for the six months ended June 30, 2012, resulting in effective tax rates of 36.4% and 38.6%, respectively. For both the 2013 and 2012 periods, our effective tax rate differs from the federal statutory rate primarily as a result of recording stock-based compensation expense and other operating expenses that are not deductible for income tax purposes as well as the effect of state income taxes. The decrease in the effective tax rate is mainly a result of the relationship of these items to book income.

Capital Resources and Liquidity

Our primary sources of liquidity since our formation in January 2002 have been net cash provided by operating activities, sales and other issuances of equity and debt securities, including our Convertible Notes and senior notes, bank credit facilities, proceeds from sale-leasebacks, joint exploration agreements and sales of interests in properties. Our primary use of capital has been for the development, exploration and acquisition of oil and natural gas properties. As we pursue profitable reserves and production growth, we continually monitor the capital resources, including issuance of equity and debt securities, available to us to meet our future financial obligations, planned capital expenditure activities and liquidity. Our future success in growing proved reserves and production will be highly dependent on capital resources available to us and our success in finding or acquiring additional reserves. We believe that we have significant liquidity available to us from cash flows from operations and under our Amended Credit Facility for our planned uses of capital. We do not intend to increase our total indebtedness at December 31, 2013 compared to December 31, 2012.

At June 30, 2013, we had cash and cash equivalents of $62.9 million and a $80.0 million balance outstanding under our Amended Credit Facility. As of June 30, 2013, the commitments on our Amended Credit Facility are $825.0 million. Our borrowing capacity is further reduced by $26.0 million to $719.0 million due to an outstanding irrevocable letter of credit related to a firm transportation agreement. Subsequent to June 30, 2013, we drew down an additional $280.0 million on the Amended Credit Facility on July 12, 2013 to fund the redemption of the 9.875% Senior Notes, resulting in a current borrowing capacity of $439.0 million.

Cash Flow from Operating Activities

Net cash provided by operating activities for the six months ended June 30, 2013 and 2012 was $123.0 million and $179.2 million, respectively. Cash provided by operating activities decreased primarily due to the 27% decrease in production volumes, which resulted in a $99.9 million reduction in revenues, offset by reductions in cash operating expenses.

Commodity Hedging Activities

Our operating cash flow is sensitive to many variables, the most significant of which is the volatility of prices for oil, natural gas and NGLs. Prices for these commodities are determined primarily by prevailing market conditions. National and worldwide economic activity and political stability, weather, infrastructure capacity to reach markets, supply levels and other variable factors influence market conditions for these products. These factors are beyond our control and are difficult to predict.

To mitigate some of the potential negative impact on cash flow caused by changes in oil, natural gas and NGL prices, we have entered into financial commodity swap contracts to receive fixed prices for a portion of our production revenue. We typically hedge a fixed price for natural gas at our sales points (NYMEX less basis) to mitigate the risk of differentials to the NYMEX Henry Hub Index. At June 30, 2013, we had in place crude oil swaps covering portions of our 2013, 2014 and 2015 production, natural gas swaps covering portions of our 2013 and 2014 production and NGL swaps covering portions of our 2013 production.

In addition to financial contracts, we may at times enter into various physical commodity contracts for the sale of oil, natural gas and NGLs that cover varying periods of time and have varying pricing provisions. These physical commodity contracts qualify for the normal purchase and normal sales exception and, therefore, are not subject to hedge or mark-to-market accounting. The financial impact of physical commodity contracts is included in oil, gas and NGL production revenues at the time of settlement.

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All derivative instruments, other than those that meet the normal purchase and normal sales exception as mentioned above, are recorded at fair market value and are included in the Unaudited Consolidated Balance Sheets as assets or liabilities. All fair values are adjusted for non-performance risk. All changes in the derivative’s fair value are recorded in earnings. These mark-to-market adjustments produce a degree of earnings volatility but have no cash flow impact relative to changes in market prices. Our cash flow is only impacted when the associated derivative instrument contract is settled by making a payment to or receiving a payment from the counterparty.

At June 30, 2013, the estimated fair value of all of our commodity derivative instruments was a net asset of $29.3 million, comprised of current and noncurrent assets and liabilities. We will reclassify the appropriate cash flow hedge amounts from AOCI, related to hedges designated as cash flow hedges prior to January 1, 2012, to gains and losses included in oil, natural gas and NGL production operating revenues as the hedged production quantities are produced.

The table below summarizes the realized and unrealized gains and losses that we recognized related to our oil and natural gas derivative instruments for the periods indicated:

	Three Months Ended June 30,					Six Months Ended June 30,
	2013			2012		2013		2012
	(in thousands)
Realized gain on derivatives designated as cash flow hedges(1)	$	1,936		$	20,798	$	4,003	$	46,263
Realized gain (loss) on derivatives not designated as cash flow hedges(2)	$	(227	)	$	18,916	$	6,226	$	22,719
Unrealized gain on derivatives not designated as cash flow hedges(2)	37,066			28,108		762		69,052
Total commodity derivative gain	$	36,839		$	47,024	$	6,988	$	91,771

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

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

The following table summarizes all of our hedges in place as of June 30, 2013:

Contract	Total Hedged Volumes	Quantity Type	Weighted Average Fixed Price		Index Price(1)	Fair Market Value (in thousands)
Swap Contracts:
2013
Natural gas	920,000	MMBtu	$	5.01	CIG	$	1,487
Natural gas	21,935,000	MMBtu	$	3.67	NWPL	5,045
Natural gas liquids(2)	160,714	Bbls	$	74.74	Mt. Belvieu	2,646
Oil	1,527,200	Bbls	$	97.62	WTI	3,794
2014
Natural gas	30,415,000	MMBtu	$	3.87	NWPL	5,231
Oil	2,205,400	Bbls	$	94.15	WTI	8,667
2015
Natural gas	3,650,000	MMbtu	$	4.25	NWPL	1,105
Oil	365,000	Bbls	$	89.31	WTI	1,341
Total						$	29,316

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The following table includes all hedges entered into subsequent to June 30, 2013 through July 19, 2013:

Contract	Total Hedged Volumes	Quantity Type	Weighted Average Fixed Price		Index Price(1)
Swap Contracts:
2014
Oil	345,400	Bbls	$	95.06	WTI

(1) CIG refers to Colorado Interstate Gas Rocky Mountains and NWPL refers to Northwest Pipeline Corporation price as quoted in Platt’s Inside FERC on the first business day of each month. Mt. Belvieu refers to the average daily price as quoted by Oil Price Information Service (“OPIS”) for Mont Belvieu spot gas liquid prices. WTI refers to West Texas Intermediate price as quoted on the New York Mercantile Exchange.

(2) Weighted average fixed price includes propane, normal butane, isobutane and natural gasoline hedges.

By removing the price volatility from a portion of our oil and natural gas related revenue for 2013, 2014 and 2015 and NGL related revenue for 2013, we have mitigated, but not eliminated, the potential effects of changing prices on our operating cash flow for those periods. While mitigating negative effects of falling commodity prices, these derivative contracts also limit the benefits we would receive from increases in commodity prices.

It is our 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 we amended the facility in October 2011. We 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. Our 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. We are not required to provide any credit support to our counterparties other than cross collateralization with the properties securing the Amended Credit Facility. We have set-off provisions in our derivative contracts with lenders under our Amended Credit Facility which, in the event of a counterparty default, allow us to set-off amounts owed to the defaulting counterparty under the Amended Credit Facility or other obligations against monies owed us under derivative contracts. Where the counterparty is not a lender under the Amended Credit Facility, we may not be able to set-off amounts owed by us under the Amended Credit Facility, even if such counterparty is an affiliate of a lender under such facility.

Capital Expenditures

Our capital expenditures are summarized in the following tables for the periods indicated:

	Six Months Ended June 30,
Basin/Area	2013		2012
	(in millions)
Piceance	$	4.3	$	148.6
Uinta – West Tavaputs	2.5		77.9
Uinta Oil Program	132.2		151.4
DJ	55.7		56.3
Powder River Oil	39.7		18.0
Other	2.9		30.1
Total	$	237.3	$	482.3

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	Six Months Ended June 30,
	2013		2012
	(in millions)
Acquisitions of proved and unproved properties and other real estate	$	7.5	$	54.0
Drilling, development, exploration and exploitation of oil and natural gas properties (1)	228.8		420.0
Geologic and geophysical costs	0.2		4.5
Furniture, fixtures and equipment	0.8		3.8
Total	$	237.3	$	482.3

(1) Includes related gathering and facilities costs.

Our current estimated capital expenditure budget in 2013 is $465.0 million to $485.0 million, with all drilling activities targeting oil. The budget includes facilities costs and excludes material acquisitions. We may adjust capital expenditures throughout the year as business conditions and operating results warrant. We believe that we have sufficient available liquidity through 2013 with available cash under the Amended Credit Facility, our hedge positions and cash flow from operations to fund our budgeted capital expenditures. Future cash flows are subject to a number of variables, including our level of oil, natural gas and NGL production, commodity prices and operating costs. There can be no assurance that operations and other capital resources will provide sufficient amounts of cash flow to maintain planned levels of capital expenditures. We do not intend to increase our total indebtedness at December 31, 2013 compared to December 31, 2012.

The amount, timing and allocation of capital expenditures is generally discretionary and within our control. If oil, natural gas and NGL prices decline to levels below our acceptable levels or costs increase to levels above our acceptable levels, we could choose to defer a portion of our budgeted capital expenditures until later periods to achieve the desired balance between sources and uses of liquidity generally by prioritizing capital projects to first focus on those that we believe will have the highest expected financial returns and ability to generate near-term cash flow. We routinely monitor and adjust our capital expenditures, including acquisitions and divestitures, in response to changes in prices and other economic and market conditions, availability of financing, drilling and acquisition costs, industry conditions, the timing of regulatory approvals, the availability of rigs, success or lack of success in drilling activities, contractual obligations, internally generated cash flow and other factors both within and outside of our control.

Financing Activities

Amended Credit Facility

Our 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 1.7% for the three months ended June 30, 2013 and 2012, and 1.7% and 1.8% for the six months ended June 30, 2013 and 2012, respectively.

The borrowing base is required to be re-determined twice per year. The borrowing base was re-affirmed at $825.0 million as of April 24, 2013 related to our normal spring re-determination. Future borrowing bases will be computed based on proved oil, natural gas and NGL reserves, hedge position and estimated future cash flows from those reserves, as well as any other outstanding debt.

The Amended Credit Facility is secured by oil and natural gas properties representing at least 80% of the value of our proved reserves and the pledge of all of the stock of our subsidiaries. The Amended Credit Facility also contains certain financial covenants. We are currently in compliance with all financial covenants and have complied with all financial covenants since origination. As of June 30, 2013, we had $80.0 million outstanding under the Amended Credit Facility. As credit support for future payment under a contractual obligation, a $26.0 million letter of credit was issued under the Amended Credit Facility, effective May 4, 2010, which reduced the borrowing capacity of the Amended Credit Facility to $719.0 million as of June 30, 2013. Subsequent to June 30, 2013 we drew down an additional $280.0 million on the Amended Credit Facility on July 12, 2013 to fund the redemption of the 9.875% Senior Notes, discussed below, resulting in a current borrowing capacity of $439.0 million.

9.875% Senior Notes Due 2016

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On July 8, 2009, we issued $250.0 million in aggregate principal amount of 9.875% Senior Notes due 2016 at 95.172% of par resulting in a discount of $12.1 million. The 9.875% Senior Notes were scheduled to mature on July 15, 2016. On June 14, 2013, we delivered a notice of redemption to the holders of the notes announcing that, pursuant to the indenture for the notes, we elected to redeem the entire outstanding $250.0 million principal amount of the notes on July 15, 2013 for a redemption price of 104.938% of the principal amount of the notes.

We drew down $280.0 million on our Amended Credit Facility on July 12, 2013 to fund the redemption of the notes, and on July 15, 2013 we paid $262.3 million to redeem the notes. As of July 15, 2013, there were amounts related to the 9.875% Senior Notes outstanding as unamortized debt discount and deferred financing costs resulting in a loss upon settlement of the 9.875% Senior Notes of $21.4 million, which will be recorded in the quarter ended September 30, 2013.

5% Convertible Senior Notes Due 2028

On March 12, 2008, we 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 us and were redeemed by us at par. We 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 us. The Convertible Notes are senior unsecured obligations and rank equal in right of payment to all of our existing and future senior unsecured indebtedness, are senior in right of payment to all of our future subordinated indebtedness, and are effectively subordinated to all of our 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 our subsidiaries. The Convertible Notes are fully and unconditionally guaranteed by the subsidiaries that guarantee our indebtedness under the Amended Credit Facility, the 9.875% Senior Notes, 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 us 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. We have the right with at least 30 days’ notice to call the Convertible Notes.

7.625% Senior Notes Due 2019

On September 27, 2011, we 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 callable by us on October 1, 2015 at 103.813% of the par value of the notes. The 7.625% Senior Notes are senior unsecured obligations and rank equal in right of payment with all of our other existing and future senior unsecured indebtedness, including the Convertible Notes, 9.875% Senior Notes, and 7.0% Senior Notes. The 7.625% Senior Notes are fully and unconditionally guaranteed by our subsidiaries that guarantee our indebtedness under the Amended Credit Facility, the Convertible Notes, the 9.875% Senior Notes and the 7.0% Senior Notes. The 7.625% Senior Notes include certain covenants that limit our ability to incur additional indebtedness, make restricted payments, create liens or sell assets and that prohibit us from paying dividends. We are currently in compliance with all financial covenants and have complied with all financial covenants since issuance. The 7.625% Senior Notes are redeemable at our 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, we 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 beginning October 15, 2012. The 7.0% Senior Notes are senior unsecured obligations and rank equal in right of payment with all of our other existing and future senior unsecured indebtedness, including the Convertible Notes, 9.875% Senior Notes and 7.625% Senior Notes. The 7.0% Senior Notes are redeemable at our 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 our subsidiaries that guarantee the Amended Credit Facility, the Convertible Notes, the 9.875% Senior Notes and the 7.625% Senior Notes. The 7.0% Senior Notes include certain covenants that limit our ability to incur additional indebtedness, make restricted payments, create liens or sell assets and that prohibit us from paying dividends. We are currently in compliance with all financial covenants and have complied with all financial covenants since issuance.

Lease Financing Obligation Due 2020

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On July 23, 2012, we entered into a lease financing arrangement with Bank of America Leasing & Capital, LLC as the lead bank (the “Lease Financing Obligation”) whereby we received $100.8 million through the sale and subsequent leaseback of existing compressors and related facilities owned by us. The Lease Financing Obligation expires on August 10, 2020, and we have 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 we 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%.

Our outstanding debt is summarized below:

		As of June 30, 2013							As of December 31, 2012
	Maturity Date	Principal		Unamortized Discount			Carrying Amount		Principal		Unamortized Discount			Carrying Amount
		(in thousands)
Amended Credit Facility (1)	October 31, 2016	$	80,000	$	—		$	80,000	$	—	$	—		$	—
9.875% Senior Notes (2)	July 15, 2016	250,000		(6,348		)	243,652		250,000		(7,209		)	242,791
Convertible Notes (3)	March 15, 2028 (4)	25,344		—			25,344		25,344		—			25,344
7.625% Senior Notes (5)	October 1, 2019	400,000		—			400,000		400,000		—			400,000
7.0% Senior Notes (6)	October 15, 2022	400,000		—			400,000		400,000		—			400,000
Lease Financing Obligation (7)	August 10, 2020	93,095		—			93,095		97,596		—			97,596
Total Debt		$	1,248,439	$	(6,348	)	$	1,242,091	$	1,172,940	$	(7,209	)	$	1,165,731
Less: Current Portion of Long-Term Debt		9,227		—			9,227		9,077		—			9,077
Total Long-Term Debt		$	1,239,212	$	(6,348	)	$	1,232,864	$	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 approximately $263.1 million and $271.9 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments. We redeemed these notes in full on July 15, 2013.

(3) The aggregate estimated fair value of the Convertible Notes was approximately $24.7 million and $25.3 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

(4) We have the right at any time with at least 30 days’ notice to call the Convertible Notes, and the holders have the right to require us 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 $417.5 million and $435.0 million as of June 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 $400.0 million and $413.8 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

(7) The aggregate estimated fair value of the Lease Financing Obligation was approximately 90.1 million and $97.7 million as of June 30, 2013 and 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.

Credit Ratings. Our credit risk is evaluated by two independent rating agencies based on publicly available information and information obtained during our ongoing discussions with the rating agencies. Moody’s Investor Services and Standard & Poor’s Rating Services currently rate our 7.625% Senior Notes and 7.0% Senior Notes and have assigned a credit rating. We do not have any provisions that are linked to our credit ratings, nor do we have any credit rating triggers that would accelerate the maturity of amounts due under our Amended Credit Facility, Convertible Notes, 7.625% Senior Notes or the 7.0% Senior Notes. However, our ability to raise funds and the costs of any financing activities will be affected by our credit rating at the time any such financing activities are conducted.

Contractual Obligations. A summary of our contractual obligations as of and subsequent to June 30, 2013 is provided in the following table:

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	Payments Due By Year
	Year 1		Year 2		Year 3		Year 4		Year 5		Thereafter		Total
	(in thousands)
Notes payable (1)	$	553	$	553	$	553	$	80,553	$	460	$	—	$	82,672
9.875% Senior Notes (2)	24,688		24,688		24,688		251,029		—		—		325,093
7.625% Senior Notes (3)	30,500		30,500		30,500		30,500		30,500		438,125		590,625
7.0% Senior Notes (4)	28,000		28,000		28,000		28,000		28,000		520,167		660,167
Convertible Notes (5)	1,267		24,418		—		—		—		—		25,685
Lease Financing Obligation (6)	12,139		12,139		12,139		12,139		12,139		26,298		86,993
Purchase commitments (7)(8)	—		—		1,681		—		—		—		1,681
Drilling commitments (8)(9)	—		1,309		—		—		—		—		1,309
Office and office equipment leases and other (10)	4,022		3,321		2,689		2,460		2,501		1,899		16,892
Firm transportation and processing agreements (8)(11)	57,769		58,089		57,686		54,052		50,996		115,316		393,908
Asset retirement obligations (12)	896		717		782		1,180		1,157		45,863		50,595
Derivative liability (13)	56		—		—		—		—		—		56
Total	$	159,890	$	183,734	$	158,718	$	459,913	$	125,753	$	1,147,668	$	2,235,676

(1) Included in notes payable is the outstanding principal amount under our Amended Credit Facility due October 31, 2016. This table does not include future commitment fees, interest expense or other fees on our Amended Credit Facility because the Amended Credit Facility is a floating rate instrument, and we cannot determine with accuracy the timing of future loan advances, repayments or future interest rates to be charged. Also included in notes payable is a $26.0 million letter of credit that accrues interest at 2.0% and 0.125% per annum for participation fees and fronting fees, respectively. The expected term for the letter of credit is April 30, 2018.

(2) On July 8, 2009, we issued $250.0 million aggregate principal amount of 9.875% Senior Notes. We redeemed the 9.875% Senior Notes in full on July 15, 2013. We made the final interest payment of $12.3 million related to the 9.875% Senior Notes on July 12, 2013.

(3) On September 27, 2011, we issued $400.0 million aggregate principal amount of 7.625% Senior Notes. We are obligated to make annual interest payments through maturity in 2019 equal to $30.5 million.

(4) On March 25, 2012, we issued $400.0 million aggregate principal amount of 7.0% Senior Notes. We are obligated to make annual interest payments through maturity in 2022 equal to $28.0 million.

(5) On March 12, 2008, we issued $172.5 million aggregate principal amount of Convertible Notes. On March 20, 2012 approximately 85% of the outstanding Convertible Notes, representing $147.2 million of the then outstanding principal amount, were put to us. We settled the notes in cash and recognized a gain on extinguishment of $1.6 million after completing a fair value analysis of the consideration transferred to holders of the Convertible Notes. After the redemption in March 2012, $25.3 million principal amount of the Convertible Notes is currently outstanding. We are obligated to make semi-annual interest payments on the Convertible Notes until either we call the remaining Convertible Notes or the holders put the Convertible Notes to us, which is expected to occur by 2015.

(6) The Lease Financing Obligation is calculated based on the aggregate undiscounted minimum future lease payments.

(7) We have one take-or-pay carbon dioxide purchasing agreement that expires in December 2015. The agreement imposes a minimum volume commitment to purchase CO2 at a contracted price. The contract provides CO2 used in fracture stimulation operations. If we do not take delivery of the minimum volume required, we are obligated to pay for the deficiency. As of June 30, 2013, $1.7 million of the future commitment is due by December 31, 2015.

(8) The values in the table represent the gross amounts that we are financially committed to pay. However, we will record in our financial statements our proportionate share based on our working interest and net revenue interest, which will vary from property to property.

(9) We currently have one drilling commitment through 2014, which requires us to drill two wells before October 31, 2014. If we do not drill the two wells, we are required to pay a contracted amount of $1.3 million.

(10) The lease for our principal offices in Denver extends through March 2019.

(11) We have entered into contracts that provide firm processing rights and firm transportation capacity on pipeline systems. The remaining terms on these contracts range from two to 11 years and require us to pay transportation demand and processing charges regardless of the amount of gas we deliver to the processing facility or pipeline.

(12) Neither the ultimate settlement amounts nor the timing of our asset retirement obligations can be precisely determined in advance. See “—Critical Accounting Policies and Estimates” below for a more detailed discussion of the nature of the accounting estimates involved in estimating asset retirement obligations.

(13) Derivative liabilities represent the net fair value for oil, gas and NGL commodity derivatives presented as liabilities in our Unaudited Consolidated Balance Sheets as of June 30, 2013. The ultimate settlement amounts of our derivative

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liabilities are unknown because they are subject to continuing market fluctuations. See “Critical Accounting Policies and Estimates” in Part II, Item 7 of our Annual Report on Form 10-K for the year ended December 31, 2012 and in “–Commodity Hedging Activities” above in this Quarterly Report on Form 10-Q for a more detailed discussion of the nature of the accounting estimates involved in valuing derivative instruments.

Trends and Uncertainties

In addition to the discussion below, we refer you to the corresponding section in Part II, Item 7 of our Annual Report on Form 10-K for the year ended December 31, 2012 for a discussion of trends and uncertainties that may affect our financial condition or liquidity.

The well completion technique known as hydraulic fracturing, used to stimulate production of natural gas and oil, has come under increased scrutiny by the environmental community, and at all levels of government. We use this completion technique on substantially all of our wells. Legislation and additional regulation has been proposed, including by ballot initiative in certain local jurisdictions, and moratoria have been imposed or proposed in certain Colorado jurisdictions where we do not currently have operations. Although it is not possible at this time to predict the outcome of legislative, regulatory and ballot initiative proposals, any new restrictions that may be imposed in areas in which we conduct business could result in increased compliance costs or additional operating restrictions. If the use of hydraulic fracturing is limited or prohibited, our future ability to develop natural gas and oil would be negatively impacted.

A substantial or extended decline in oil, natural gas or NGL prices may result in impairments of our proved oil and gas properties and may materially and adversely affect our future business, financial condition, results of operations, liquidity or ability to finance planned capital expenditures. We are currently exploring several property sales or other alternatives which may or may not result in future impairments or losses. To the extent commodity prices or volumes received from production are insufficient to fund planned capital expenditures, we will be required to reduce spending or to fund that shortfall through borrowings under our Amended Credit Facility or from sales of properties or debt or equity financings, which may not be on advantageous terms in low commodity price environments. We have protected the cash flow from approximately 70% of our anticipated 2013 production and a portion of our anticipated 2014 and 2015 production with hedges. However our ability to hedge at price levels similar to those for prior years is unlikely given current futures prices, which will likely result in a decline in our revenue per unit of production.

Critical Accounting Policies and Estimates

We refer you to the corresponding section in Part II, Item 7 of our Annual Report on Form 10-K for the year ended December 31, 2012 and the notes to the Unaudited Consolidated Financial Statements included in Item 1 of this Quarterly Report on Form 10-Q for a description of critical accounting policies and estimates. 

Item 3. Quantitative and Qualitative Disclosures about Market Risk.

The primary objective of the following information is to provide forward-looking quantitative and qualitative information about our potential exposure to market risks. The term “market risk” refers to the risk of loss arising from adverse changes in oil, natural gas and NGL prices and interest rates. The disclosures are not meant to be precise indicators of expected future losses, but rather indicators of reasonably possible losses. This forward-looking information provides indicators of how we view and manage our ongoing market risk exposures. All of our market risk sensitive instruments were entered into for purposes other than speculative trading.

Commodity Price Risk

Our primary market risk exposure is in the prices we receive for our production. Realized pricing is primarily driven by the prevailing worldwide price for crude oil and spot regional market prices applicable to our U.S. natural gas production. Pricing for oil, natural gas and NGLs has been volatile and unpredictable for several years, and we expect this volatility to continue in the future. The prices we receive for future production depend on many factors outside of our control, including volatility in the differences between product prices at sales points and the applicable index price. Based on our average daily production and our derivative contracts in place for the six months ended June 30, 2013, our annual income before income taxes would have decreased by approximately $0.4 million for each $1.00 per barrel decrease in crude oil prices, $0.8 million for each $0.10 decrease per MMBtu in natural gas prices and $0.5 million for each $1.00 per barrel decrease in NGL prices. We are more susceptible to proved and unproved property impairments due to the current commodity price environment.

We routinely enter into commodity hedges relating to a portion of our projected production revenue through various financial transactions that hedge future prices received. These transactions may include financial price swaps whereby we will receive a fixed price and pay a variable market price to the contract counterparty. These commodity hedging activities are

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intended to support oil, natural gas and NGL prices at targeted levels that provide an acceptable rate of return and to manage our exposure to oil, natural gas and NGL price fluctuations.

As of July 19, 2013, we have financial derivative instruments related to oil, natural gas and NGL volumes in place for the following periods indicated. Further detail of these hedges is summarized in the table presented under “Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations— Capital Resources and Liquidity— Commodity Hedging Activities.”

	July – December 2013	For the year 2014	For the year 2015
Oil (Bbls)	1,527,200	2,624,400	365,000
Natural Gas (MMbtu)	22,855,000	30,415,000	3,650,000
Natural Gas Liquids (Bbls)	160,714	—	—

Interest Rate Risks

At June 30, 2013, we had $80.0 million outstanding under our Amended Credit Facility, which bears interest at floating rates. The average annual interest rate incurred on this debt for the six months ended June 30, 2013 was 1.2%. A 1.0% increase in each of the average LIBOR rate and federal funds rate for the six months ended June 30, 2013 would have resulted in an estimated $0.3 million increase in interest expense assuming a similar average debt level to the six months ended June 30, 2013. The average annual interest rate incurred on this debt for the six months ended June 30, 2012 was 1.8%. A 1.0% increase in each of the average LIBOR rate and federal funds rate for the six months ended June 30, 2012 would have resulted in an estimated $0.3 million increase in interest expense assuming a similar average debt level to the six months ended June 30, 2012. We also had $25.3 million principal amount of Convertible Notes (with a fixed cash interest rate of 5%), $250.0 million principal amount of 9.875% Senior Notes, $400.0 million principal amount of 7.625% Senior Notes, $400.0 million principal amount of 7.0% Senior Notes and $93.1 million principal amount of 3.3% Lease Financing Obligation outstanding at June 30, 2013.

Item 4. Controls and Procedures.

Evaluation of Disclosure Controls and Procedures. As of June 30, 2013, we carried out an evaluation, under the supervision and with the participation of management, including the Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of our disclosure controls and procedures pursuant to Rules 13a-15 and 15d-15 of the Securities Exchange Act of 1934 (the “Exchange Act”). Based upon that evaluation, the Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures are effective as of June 30, 2013.

Changes in Internal Controls. There has been no change in our internal control over financial reporting during the second fiscal quarter of 2013 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

PART II. OTHER INFORMATION

Item 1.   Legal Proceedings.

We are not a party to any material pending legal or governmental proceedings, other than ordinary routine litigation incidental to our business. While the ultimate outcome and impact of any proceeding cannot be predicted with certainty, our management believes that the resolution of any proceeding will not have a material effect on our financial condition or results of operations.

Item 1A. Risk Factors.

As of the date of this filing, there have been no material changes or updates to the risk factors previously disclosed in the “Risk Factors” section of our Annual Report on Form 10-K for the year ended December 31, 2012. An investment in our securities involves various risks. When considering an investment in our Company, you should carefully consider all of the risk factors described in our Annual Report on Form 10-K for the year ended December 31, 2012 and subsequent reports filed with the SEC. These risks and uncertainties are not the only ones facing us, and there may be additional matters that we are unaware of or that we currently consider immaterial. All of these could adversely affect our business, financial condition, results of operations and cash flows and, thus, the value of an investment in our Company.

Item 2.   Unregistered Sales of Equity Securities and Use of Proceeds.

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Unregistered Sales of Securities

There were no sales of unregistered equity securities during the period covered by this report.

Issuer Purchases of Equity Securities

The following table contains information about our acquisitions of equity securities during the three months ended June 30, 2013:

Period	Total Number of Shares (1)	Weighted Average Price Paid Per Share		Total Number of  Shares (or Units) Purchased as Part of Publicly Announced Plans or Programs	Maximum Number  (or Approximate  Dollar Value) of Shares (or Units) that May Yet Be Purchased Under the Plans or Programs
April 1 – 30, 2013	388	$	20.25	—	—
May 1 – 31, 2013	2,985	21.86		—	—
June 1 – 30, 2013	61	22.08		—	—
Total	3,434	$	21.69	—	—

(1) Represents shares delivered by employees to satisfy the exercise price of stock options and tax withholding obligations in connection with the exercise of stock options and shares withheld from employees to satisfy tax withholding obligations in connection with the vesting of restricted shares of common stock issued pursuant to our employee incentive plans.

Item 3.    Defaults upon Senior Securities.

Not applicable.

Item 4.    Mine Safety Disclosures.

Not applicable.

Item 5.    Other Information.

Not applicable.

Item 6.   Exhibits.

Exhibit Number	Description of Exhibits
2	Purchase and Sale Agreement dated October 31, 2012 between Bill Barrett Corporation and Bill Barrett CBM Corporation, as Sellers, Encore Energy Partners Operating, LLC, as Buyer, and Vanguard Natural Resources LLC as Parent Guarantor. [Incorporated by reference to Exhibit 2 of our Current Report on Form 8-K filed with the Commission on November 5, 2012.]
3.1	Restated Certificate of Incorporation of Bill Barrett Corporation. [Incorporated by reference to Appendix A to our Definitive Proxy Statement filed with the Commission on April 4, 2012.]
3.2	Bylaws of Bill Barrett Corporation. [Incorporated by reference to Exhibit 3.2 of our Current Report on Form 8-K filed with the Commission on May 15, 2012.]

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4.1(a)	Specimen Certificate of Common Stock. [Incorporated by reference to Exhibit 4.1 of Amendment No. 1 to our Registration Statement on Form 8-A filed with the Commission on December 20, 2004.]
4.1(b)	Indenture, dated March 12, 2008, between Bill Barrett Corporation and Deutsche Bank Trust Company Americas, as Trustee. [Incorporated by reference to Exhibit 4.1 of our Current Report on Form 8-K filed with the Commission on March 12, 2008.]
4.1(c)	Indenture, dated July 8, 2009, between Bill Barrett Corporation and Deutsche Bank Trust Company Americas, as Trustee. [Incorporated by reference to Exhibit 4.1 of our Current Report on Form 8-K filed with the Commission on July 8, 2009.]
4.2(a)	Registration Rights Agreement, dated March 28, 2002, among Bill Barrett Corporation and the investors named therein. [Incorporated by reference to Exhibit 4.2 of Amendment No. 2 to our Registration Statement on Form S-1 (Registration No. 333-114554) filed with the Commission on August 31, 2004.]
4.2(b)	First Supplemental Indenture, dated March 12, 2008, by and between Bill Barrett Corporation and Deutsche Bank Trust Company Americas, as Trustee (including form of 5% Convertible Senior Notes due 2028). [Incorporated by reference to Exhibit 4.2 of our Current Report on Form 8-K filed with the Commission on March 12, 2008.]
4.2(c)	First Supplemental Indenture, dated July 8, 2009, by Bill Barrett Corporation and Deutsche Bank Trust Company Americas, as Trustee (including form of 9.875% Senior Notes due 2016). [Incorporated by reference to Exhibit 4.2 of our Current Report on Form 8-K filed with the Commission on July 8, 2009.]
4.3(a)	Stockholders’ Agreement, dated March 28, 2002 and as amended to date, among Bill Barrett Corporation and the investors named therein. [Incorporated by reference to Exhibit 4.3 to Amendment No. 2 to our Registration Statement on Form S-1 (Registration No. 333-114554) filed with the Commission on August 31, 2004.]
4.3(b)	Second Supplemental Indenture, dated July 8, 2009, by Bill Barrett Corporation, Bill Barrett CBM Corporation, Bill Barrett CBM LLC, Circle B Land Company LLC and Deutsche Bank Trust Company Americas, as Trustee (including form of 9.875% Senior Notes due 2016). [Incorporated by reference to Exhibit 4.3 of our Current Report on Form 8-K filed with the Commission on July 8, 2009.]
4.3(c)	Third Supplemental Indenture, dated September 27, 2011, by Bill Barrett Corporation, Bill Barrett CBM Corporation, Bill Barrett CBM LLC, Circle B Land Company LLC, GB Acquisition Corporation, Elk Production, LLC, Aurora Gathering, LLC and Deutsche Bank Trust Company Americas, as Trustee (including form of 7.625% Senior Notes due 2019). [Incorporated by reference to Exhibit 4.2 of our Current Report on Form 8-K filed with the Commission on September 27, 2011.]
4.3(d)	Fourth Supplemental Indenture for the Company’s 7% Senior Notes due 2022, dated March 12, 2012, among the Company, the Subsidiary Guarantors and the Trustee. [Incorporated by reference to Exhibit 4.2 of our Current Report on Form 8-K filed with the Commission on March 12, 2012.]

49

4.4	Form of Rights Agreement concerning Shareholder Rights Plan, which includes, as Exhibit A thereto, the Certificate of Designations of Series A Junior Participating Preferred Stock of Bill Barrett Corporation, and, as Exhibit B thereto, the Form of Right Certificate. [Incorporated by reference to Exhibit 4.4 to Amendment No. 1 to our Registration Statement on Form 8-A filed with the Commission on December 20, 2004.]
4.5	Form of Certificate of Designations of Series A Junior Participating Preferred Stock of Bill Barrett Corporation. [Incorporated by reference to Exhibit 4.4 (Exhibit A) to Amendment No. 1 to our Registration Statement on Form 8-A filed with the Commission on December 20, 2004.]
4.6	Form of Right Certificate. [Incorporated by reference to Exhibit 4.4 (Exhibit A) to Amendment No. 1 to our Registration Statement on Form 8-A filed with the Commission on December 20, 2004.]
31.1	Rule 13a-14(a)/15d-14(a) Certification of Chief Executive Officer.
31.2	Rule 13a-14(a)/15d-14(a) Certification of Chief Financial Officer.
32.1	Section 1350 Certification of Chief Executive Officer.
32.2	Section 1350 Certification of Chief Financial Officer.
101	The following materials from the Bill Barrett Corporation Quarterly Report on Form 10-Q for the quarter ended June 30, 2013 (and related periods), formatted in XBRL (eXtensible Business Reporting Language) include (i) the Unaudited Consolidated Balance Sheets, (ii) the Unaudited Consolidated Statements of Operations, (iii) the Unaudited Consolidated Statements of Stockholders’ Equity, (iv) the Unaudited Consolidated Statements Comprehensive Income (Loss), (v) the Unaudited Consolidated Statements of Cash Flows, and (vi) Notes to the Unaudited Consolidated Financial Statements.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

		BILL BARRETT CORPORATION
Date:	August 2, 2013	By:	/s/ R. Scot Woodall
			R. Scot Woodall
			Chief Executive Officer and President
			(Principal Executive Officer)
Date:	August 2, 2013	By:	/s/ Robert W. Howard
			Robert W. Howard
			Chief Financial Officer
			(Principal Financial Officer)

51

EX-31.1

Exhibit 31.1

CERTIFICATION

I, R. Scot Woodall, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Bill Barrett Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: August 2, 2013

/s/ R. Scot Woodall

R. Scot Woodall

Chief Executive Officer and President

(Principal Executive Officer)

EX-31.2

Exhibit 31.2

CERTIFICATION

I, Robert W. Howard, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Bill Barrett Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: August 2, 2013

/s/ Robert W. Howard

Robert W. Howard

Chief Financial Officer

(Principal Financial Officer)

EX-32.1

Exhibit 32.1

BILL BARRETT CORPORATION

SARBANES-OXLEY ACT SECTION 906 CERTIFICATION

In connection with this quarterly report on Form 10-Q of Bill Barrett Corporation for the fiscal quarter ended March 31, 2013, I, R. Scot Woodall, Chief Executive Officer, President and Chief Operating Officer of Bill Barrett Corporation, hereby certify pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

1. This Form 10-Q for the fiscal quarter ended March 31, 2013 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in this Form 10-Q for the fiscal quarter ended March 31, 2013 fairly presents, in all material respects, the financial condition and results of operations of Bill Barrett Corporation for the periods presented therein.

Date: August 2, 2013

/s/ R. Scot Woodall

R. Scot Woodall

Chief Executive Officer and President

(Principal Executive Officer)

EX-32.2

Exhibit 32.2

BILL BARRETT CORPORATION

SARBANES-OXLEY ACT SECTION 906 CERTIFICATION

In connection with this quarterly report on Form 10-Q of Bill Barrett Corporation for the fiscal quarter ended March 31, 2013, I, Robert W. Howard, Chief Financial Officer of Bill Barrett Corporation, hereby certify pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

1. This Form 10-Q for the fiscal quarter ended March 31, 2013 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in this Form 10-Q for the fiscal quarter ended March 31, 2013 fairly presents, in all material respects, the financial condition and results of operations of Bill Barrett Corporation for the periods presented therein.

Date: August 2, 2013

/s/ Robert W. Howard

Robert W. Howard

Chief Financial Officer

(Principal Financial Officer)

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Income Taxes

6 Months Ended

Jun. 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 six months ended June 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 six months ended June 30, 2013.

Income tax expense for the three and six months ended June 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.

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Derivative Instruments - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2013 Counterparty
Derivative Instruments And Hedging Activities [Line Items]
Number of counterparties for hedges at period end	11

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CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Operating and Other Revenues:
Oil, gas and NGL production	$ 140,380	$ 159,490	$ 274,785	$ 336,532
Other	1,919	862	5,791	2,996
Total operating and other revenues	142,299	160,352	280,576	339,528
Operating Expenses:
Lease operating expense	16,112	19,030	34,858	37,668
Gathering, transportation and processing expense	18,772	25,862	34,360	53,214
Production tax expense	7,781	6,892	13,732	13,099
Exploration expense	141	4,062	236	4,501
Impairment, dry hole costs and abandonment expense	1,182	21,075	8,283	21,639
Depreciation, depletion and amortization	74,307	85,942	142,745	160,025
General and administrative expense	13,273	15,036	33,855	33,476
Total operating expenses	131,568	177,899	268,069	323,622
Operating Income (Loss)	10,731	(17,547)	12,507	15,906
Other Income and Expense:
Interest and other income	32	113	71	75
Interest expense	(24,726)	(23,912)	(49,268)	(45,502)
Commodity derivative gain	36,839	47,024	6,988	91,771
Gain on extinguishment of debt	0	0	0	1,601
Total other income and expense	12,145	23,225	(42,209)	47,945
Income (Loss) before Income Taxes	22,876	5,678	(29,702)	63,851
Provision for (Benefit from) Income Taxes	8,603	2,380	(10,824)	24,660
Net Income (Loss)	$ 14,273	$ 3,298	$ (18,878)	$ 39,191
Net Income (Loss) Per Common Share, Basic	$ 0.30	$ 0.07	$ (0.40)	$ 0.83
Net Income (Loss) Per Common Share, Diluted	$ 0.30	$ 0.07	$ (0.40)	$ 0.83
Weighted Average Common Shares Outstanding, Basic	47,468,569	47,201,954	47,411,054	47,143,430
Weighted Average Common Shares Outstanding, Diluted	47,615,871	47,245,167	47,411,054	47,334,507

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Summary of Significant Accounting Policies

6 Months Ended

Jun. 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 June 30, 2013			As of December 31, 2012
	(in thousands)
Accrued oil, gas and NGL sales	$	61,749		$	69,482
Due from joint interest owners	29,568			36,300
Other	4,163			6,554
Allowance for doubtful accounts	(23		)	(325		)
Total accounts receivable	$	95,457		$	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 June 30, 2013			As of December 31, 2012
	(in thousands)
Proved properties	$	439,312		$	387,242
Wells and related equipment and facilities	2,830,443			2,625,891
Support equipment and facilities	315,910			304,914
Materials and supplies	15,550			13,220
Total proved oil and gas properties	$	3,601,215		$	3,331,267
Unproved properties	322,364			384,486
Wells and facilities in progress	78,853			72,721
Total unproved oil and gas properties, excluded from amortization	$	401,217		$	457,207
Accumulated depreciation, depletion, amortization and impairment	(1,329,493		)	(1,203,495		)
Total oil and gas properties, net	$	2,672,939		$	2,584,979

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 June 30, 2013, 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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Non-cash impairment of proved oil and gas properties	$	—	$	—	$	—	$	—
Non-cash impairment of unproved oil and gas properties	—		18,337		—		18,337
Dry hole costs	113		42		964		233
Abandonment expense	1,069		2,696		7,319		3,069
Total non-cash impairment, dry hole costs and abandonment expense	$	1,182	$	21,075	$	8,283	$	21,639

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 June 30, 2013		As of December 31, 2012
	(in thousands)
Accrued drilling, completion and facility costs	$	60,572	$	42,094
Accrued lease operating, gathering, transportation and processing expenses	18,393		16,862
Accrued general and administrative expenses	7,530		13,054
Trade payables and other	34,224		53,007
Total accounts payable and accrued liabilities	$	120,719	$	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 June 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 Per Share. Basic net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding during each period. Diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding and other dilutive securities. Potentially dilutive securities for the diluted net income (loss) 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.

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 June 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 income (loss) per common share calculation for the three and six months ended June 30, 2013 and 2012. The diluted net income (loss) per common share excludes the anti-dilutive effect of 2,857,757 and 3,771,662 shares of stock options and nonvested performance-based shares of common stock for the three months ended June 30, 2013 and 2012, respectively, and 2,836,480 and 2,896,452 shares of stock options and nonvested performance-based shares of common stock for the six months ended June 30, 2013 and 2012, respectively.

The following table sets forth the calculation of basic and diluted earnings per share:

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013			2012
	(in thousands, except per share amounts)
Net income (loss)	$	14,273	$	3,298	$	(18,878	)	$	39,191
Basic weighted-average common shares outstanding in period	47,469		47,202		47,411			47,143
Add dilutive effects of stock options and nonvested equity shares of common stock	147		43		—			192
Diluted weighted-average common shares outstanding in period	47,616		47,245		47,411			47,335
Basic net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83
Diluted net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83

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 Update 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 FASB 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.

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Supplemental Disclosures of Cash Flow Information (Tables)

6 Months Ended

Jun. 30, 2013

Supplemental Cash Flow Elements [Abstract]

Supplemental Cash Flow Information

Supplemental cash flow information is as follows:

	Six Months Ended June 30,
	2013			2012
	(in thousands)
Cash paid for interest, net of amount capitalized	$	45,709		$	34,656
Cash paid for income taxes	1,861			8
Supplemental disclosures of non-cash investing and financing activities:
Current liabilities	68,731			75,112
Net increase (decrease) in asset retirement obligations	1,888			(545		)
Retirement of treasury stock	(1,337		)	(2,323		)

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Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	$ 123,029	$ 179,244
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(216,652)	(460,059)
Additions to furniture, fixtures and other	(1,187)	(4,241)
Proceeds from sale of properties and other investing activities	4,086	134
Cash flows from financing activities:
Proceeds from debt	80,000	525,000
Principal payments on debt	(4,501)	(267,156)
Intercompany transfers	0	0
Other financing activities	(1,345)	(9,419)
Decrease in Cash and Cash Equivalents	(16,570)	(36,497)
Beginning Cash and Cash Equivalents	79,445	57,331
Ending Cash and Cash Equivalents	62,875	20,834
Parent Issuer
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	112,350	175,577
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(203,397)	(451,421)
Additions to furniture, fixtures and other	731	(4,241)
Proceeds from sale of properties and other investing activities	4,086	134
Cash flows from financing activities:
Proceeds from debt	80,000	525,000
Principal payments on debt	(4,501)	(267,156)
Intercompany transfers	(4,494)	(4,971)
Other financing activities	(1,345)	(9,419)
Decrease in Cash and Cash Equivalents	(16,570)	(36,497)
Beginning Cash and Cash Equivalents	79,395	57,281
Ending Cash and Cash Equivalents	62,825	20,784
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	10,679	3,667
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(13,255)	(8,638)
Additions to furniture, fixtures and other	(1,918)	0
Proceeds from sale of properties and other investing activities	0	0
Cash flows from financing activities:
Proceeds from debt	0	0
Principal payments on debt	0	0
Intercompany transfers	4,494	4,971
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 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

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Equity Incentive Compensation Plans and Other Employee Benefits - Stock Options and Nonvested Equity Shares, Equity Awards Granted (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options to purchase shares of common stock, Number of Options	0	9,576	0	555,682
Options to purchase shares of common stock, Weighted Average Price Per Share	$ 0.00	$ 23.47	$ 0.00	$ 27.49
Nonvested equity shares, Number of Shares	16,880	24,617	557,260	229,114
Nonvested equity common stock units, Number of Shares	43,824	0	52,219	0
Nonvested performance-based equity shares, Number of Shares	13,007	4,221	287,986	176,587
Total shares granted	73,711	28,838	897,465	405,701
Nonvested equity shareps	$ 19.54	$ 23.54	$ 17.32	$ 26.67
Nonvested equity common stock units, Weighted Average Grant Date Fair Value	$ 22.38	$ 0.00	$ 22.04	$ 0.00
Nonvested performance-based equity shares, Weighted Average Grant Date Fair Value	$ 17.26	$ 23.58	$ 16.60	$ 27.65

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Equity Incentive Compensation Plans and Other Employee Benefits

6 Months Ended

Jun. 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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Common stock options	$	727	$	1,573	$	3,217	$	3,673
Nonvested equity common stock	1,588		1,797		3,988		3,774
Nonvested equity common stock units	312		—		712		—
Nonvested performance-based equity	530		388		698		803
Total	$	3,157	$	3,758	$	8,615	$	8,250

Unrecognized compensation cost as of June 30, 2013 was $22.5 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 2.5 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 June 30, 2013			Three Months Ended June 30, 2012
	Number of Options	Weighted Average Price Per Share		Number of Options	Weighted Average Price Per Share
Options to purchase shares of common stock	—	$	—	9,576	$	23.47
	Three Months Ended June 30, 2013			Three Months Ended June 30, 2012
	Number of Shares	Weighted Average Grant Date Fair Value Per Share		Number of Shares	Weighted Average Grant Date Fair Value Per Share
Nonvested equity common stock	16,880	$	19.54	24,617	$	23.54
Nonvested equity common stock units	43,824	$	22.38	—	$	—
Nonvested performance-based equity shares	13,007	$	17.26	4,221	$	23.58
Total shares granted	73,711			28,838

	Six Months Ended June 30, 2013			Six Months Ended June 30, 2012
	Number of Options	Weighted Average Price Per Share		Number of Options	Weighted Average Price Per Share
Options to purchase shares of common stock	—	$	—	555,682	$	27.49
	Six Months Ended June 30, 2013			Six Months Ended June 30, 2012
	Number of Shares	Weighted Average Grant Date Fair Value Per Share		Number of Shares	Weighted Average Grant Date Fair Value Per Share
Nonvested equity common stock	557,260	$	17.32	229,114	$	26.67
Nonvested equity common stock units	52,219	$	22.04	—	$	—
Nonvested performance-based equity shares	287,986	$	16.60	176,587	$	27.65
Total shares granted	897,465			405,701

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 six months ended June 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 $0.2 million of non-cash stock-based compensation expense for the six months ended June 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 June 30, 2013 and 2012, respectively, and $0.1 million and $0.4 million of non-cash stock-based compensation expense for the six months ended June 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 were subject to the new grant date on February 27, 2013, and the fair value was remeasured at the grant date. All remaining unvested shares could potentially vest if all performance goals are met at the stretch level. 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 of non-cash stock-based compensation expense related to these awards during the three months ended June 30, 2013, and $0.2 million for the six months ended June 30, 2013.

In February 2013, the Compensation Committee established vesting terms of the Company’s nonvested equity awards in the 2010 Program that are subject to a market performance-based vesting condition, which is based on the Company’s TSR ranking relative to a defined peer group’s individual TSRs. In February 2013, 22,710 market-based nonvested equity shares of common stock were subject to the new grant date on February 27, 2013, and the fair value was remeasured at the grant date. 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 of non-cash stock-based compensation expense related to these awards for the three months ended June 30, 2013, and $0.05 million for the six months ended June 30, 2013.

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 13,007 and 287,986 shares were granted under this program during the three and six months ended June 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 $0.3 million of non-cash stock-based compensation expense related to these awards for the three months ended June 30, 2013, and $0.4 million for the six months ended June 30, 2013.

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 six months ended June 30, 2013 and 2012 is presented below:

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
Director fees (shares)	3,511		1,657		11,906		3,175
Stock-based compensation (in thousands)	$	71	$	36	$	241	$	75

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 $0.3 million and $0.4 million for the three months ended June 30, 2013 and 2012, respectively, and $1.2 million for both the six months ended June 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 $0.8 million and $1.0 million as of June 30, 2013 and December 31, 2012, respectively, of which $0.3 million was classified as current as of both June 30, 2013 and December 31, 2012.

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.

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Derivative Instruments - Fair Value Amounts of Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	$ 33,172		$ 40,432
Gross Amounts Offset in the Balance Sheet	(3,800)		(7,471)
Net Amounts of Assets Presented in the Balance Sheet	29,372		32,961
Gross Amounts of Recognized Liabilities	(3,856)		(7,875)
Gross Amounts Offset in the Balance Sheet	3,800		7,471
Net Amounts of Liabilities Presented in the Balance Sheet	(56)		(404)
Derivative Assets
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	22,898		34,828
Gross Amounts Offset in the Balance Sheet	(3,317)	[1]	(4,848)	[1]
Net Amounts of Assets Presented in the Balance Sheet	19,581		29,980
Deferred Financing Costs, Derivative Assets and Other Non Current Assets
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	10,274		5,604
Gross Amounts Offset in the Balance Sheet	(483)	[1]	(2,623)	[1]
Net Amounts of Assets Presented in the Balance Sheet	9,791	[2]	2,981	[2]
Derivative Liabilities
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities	(3,373)		(4,848)
Gross Amounts Offset in the Balance Sheet	3,317	[3]	4,848	[3]
Net Amounts of Liabilities Presented in the Balance Sheet	(56)		0
Derivative and Other Non Current Liabilities
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities	(483)		(3,027)
Gross Amounts Offset in the Balance Sheet	483	[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 June 30, 2013 and December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $24.1 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.

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Equity Incentive Compensation Plans and Other Employee Benefits - Stock Options and Nonvested Equity Shares, Equity Awards Granted (Parenthetical) (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested equity shares, Number of Shares	16,880	24,617	557,260	229,114
Nonvested equity shares, Weighted Average Grant Date Fair Value	$ 19.54	$ 23.54	$ 17.32	$ 26.67

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Supplemental Disclosures of Cash Flow Information - Supplemental Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Supplemental Cash Flow Information [Abstract]
Cash paid for interest, net of amount capitalized	$ 45,709	$ 34,656
Cash paid for income taxes	1,861	8
Supplemental disclosures of non-cash investing and financing activities:
Current liabilities	68,731	75,112
Net increase (decrease) in asset retirement obligations	1,888	(545)
Retirement of treasury stock	$ (1,337)	$ (2,323)

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Fair Value Measurements (Tables)

6 Months Ended

Jun. 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 June 30, 2013
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Deferred Compensation Plan	$	824	$	—	$	—	$	824
Cash Equivalents - Money Market Funds	8,562		—		—		8,562
Commodity Derivatives	—		33,172		—		33,172
Liabilities
Commodity Derivatives	$	—	$	3,856	$	—	$	3,856

	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

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Asset Retirement Obligations (Tables)

6 Months Ended

Jun. 30, 2013

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Asset Retirement Obligations

A reconciliation of the Company’s asset retirement obligations for the six months ended June 30, 2013 is as follows (in thousands):

As of December 31, 2012	$	47,616
Liabilities incurred	1,009
Liabilities settled	(623		)
Disposition of properties	(330		)
Accretion expense	1,707
Revisions to estimate	1,216
As of June 30, 2013	$	50,595
Less: current asset retirement obligations	896
Long-term asset retirement obligations	$	49,699

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Fair Value Measurements - Fair Value, Balance Sheet Grouping (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Assets
Deferred Compensation Plan	$ 824	$ 966
Cash Equivalents - Money Market Funds	62,875	79,445	20,834	57,331
Cash Equivalents - Money Market Funds
Assets
Cash Equivalents - Money Market Funds	8,562	53
Commodity Derivatives
Assets
Commodity Derivatives, Assets	33,172	40,432
Liabilities
Fair value liabilities disclosure	3,856	7,875
Level 1
Assets
Deferred Compensation Plan	824	966
Level 1 | Cash Equivalents - Money Market Funds
Assets
Cash Equivalents - Money Market Funds	8,562	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	33,172	40,432
Liabilities
Fair value liabilities disclosure	3,856	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

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Summary of Significant Accounting Policies - Net Capitalized Costs and Associated Accumulated Depreciation, Depletion & Amortization and Non Cash Impairments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Proved properties	$ 439,312	$ 387,242
Wells and related equipment and facilities	2,830,443	2,625,891
Support equipment and facilities	315,910	304,914
Materials and supplies	15,550	13,220
Total proved oil and gas properties	3,601,215	3,331,267
Unproved properties	322,364	384,486
Wells and facilities in progress	78,853	72,721
Total unproved oil and gas properties, excluded from amortization	401,217	457,207
Accumulated depreciation, depletion, amortization and impairment	(1,329,493)	(1,203,495)
Total oil and gas properties, net	$ 2,672,939	$ 2,584,979

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Long-Term Debt - Outstanding Debt (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Principal amount of debt instrument	$ 1,239,212,000		$ 1,163,863,000
Discount	(6,348,000)		(7,209,000)
Amount	1,232,864,000		1,156,654,000
Amended Credit Facility
Debt Instrument [Line Items]
Maturity Date	Oct. 31, 2016	[1]
Principal amount of debt instrument	80,000,000	[1]	0	[1]
Discount	0	[1]	0	[1]
Amount	80,000,000	[1]	0	[1]
9.875% Senior Notes
Debt Instrument [Line Items]
Maturity Date	Jul. 15, 2016	[2]
Principal amount of debt instrument	250,000,000	[2]	250,000,000	[2]
Discount	(6,348,000)	[2]	(7,209,000)	[2]
Amount	243,652,000	[2]	242,791,000	[2]
Convertible Notes
Debt Instrument [Line Items]
Maturity Date	Mar. 15, 2028	[3]
Principal amount of debt instrument	25,344,000	[3]	25,344,000	[3]
Discount	0	[3]	0	[3]
Amount	25,344,000	[3]	25,344,000	[3]
7.625% Senior Notes
Debt Instrument [Line Items]
Maturity Date	Oct. 01, 2019	[4]
Principal amount of debt instrument	400,000,000	[4]	400,000,000	[4]
Discount	0	[4]	0	[4]
Amount	400,000,000	[4]	400,000,000	[4]
7.0% Senior Notes
Debt Instrument [Line Items]
Maturity Date	Oct. 15, 2022	[5]
Principal amount of debt instrument	400,000,000	[5]	400,000,000	[5]
Discount	0	[5]	0	[5]
Amount	400,000,000	[5]	400,000,000	[5]
Lease Financing Obligation
Debt Instrument [Line Items]
Maturity Date	Aug. 10, 2020	[6]
Principal amount of debt instrument	93,095,000	[6]	97,596,000	[6]
Discount	0	[6]	0	[6]
Amount	93,095,000	[6]	97,596,000	[6]
Long-term Debt
Debt Instrument [Line Items]
Principal amount of debt instrument	1,248,439,000		1,172,940,000
Discount	(6,348,000)		(7,209,000)
Amount	1,242,091,000		1,165,731,000
Current Portion of Long-Term Debt
Debt Instrument [Line Items]
Principal amount of debt instrument	9,227,000		9,077,000
Discount	0		0
Amount	$ 9,227,000		$ 9,077,000

[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 approximately $263.1 million and $271.9 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013. See Note 13.

[3] The aggregate estimated fair value of the Convertible Notes was approximately $24.7 million and $25.3 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

[4] The aggregate estimated fair value of the 7.625% Senior Notes was approximately $417.5 million and $435.0 million as of June 30, 2013 and December 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 $400.0 million and $413.8 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

[6] The aggregate estimated fair value of the Lease Financing Obligation was approximately $90.1 million and $97.7 million as of June 30, 2013 and 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.

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Derivative Instruments - Fair Value Amounts of Derivative Instruments (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Balance included in other noncurrent liabilities excluding deferred financing costs and other noncurrent assets	$ 24.1	$ 26.8
Derivative Liabilities
Derivatives, Fair Value [Line Items]
Balance included in other noncurrent liabilities excluding hedge instruments		$ 4.1

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Guarantor Subsidiaries (Tables)

6 Months Ended

Jun. 30, 2013

Text Block [Abstract]

Schedule of Condensed Consolidating Balance Sheets

Condensed Consolidating Balance Sheets

	As of June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Assets:
Current assets	$	180,787		$	2,437		$	—	$	183,224
Property and equipment, net	2,589,265			108,789			—		2,698,054
Intercompany receivable (payable)	146,236			(146,236		)	—		—
Investment in subsidiaries	(40,663		)	—			40,663		—
Noncurrent assets	33,889			—			—		33,889
Total assets	$	2,909,514		$	(35,010	)	$	40,663	$	2,915,167
Liabilities and Stockholders’ Equity:
Current liabilities	$	201,900		$	845		$	—	$	202,745
Long-term debt	1,232,864			—			—		1,232,864
Deferred income taxes	253,194			2,251			—		255,445
Other noncurrent liabilities	51,734			2,557			—		54,291
Stockholders’ equity	1,169,822			(40,663		)	40,663		1,169,822
Total liabilities and stockholders’ equity	$	2,909,514		$	(35,010	)	$	40,663	$	2,915,167

	As of December 31, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(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 June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	135,631		$	6,668		$	—		$	142,299
Operating expenses	(114,207		)	(4,088		)	—			(118,295		)
General and administrative	(13,273		)	—			—			(13,273		)
Interest income and other income	12,145			—			—			12,145
Income before income taxes and equity in earnings of subsidiaries	20,296			2,580			—			22,876
Provision for income taxes	(8,603		)	—			—			(8,603		)
Equity in earnings of subsidiaries	2,580			—			(2,580		)	—
Net income	$	14,273		$	2,580		$	(2,580	)	$	14,273

	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	265,771		$	14,805		$	—		$	280,576
Operating expenses	(226,279		)	(7,935		)	—			(234,214		)
General and administrative	(33,855		)	—			—			(33,855		)
Interest income and other income (expense)	(42,209		)	—			—			(42,209		)
Income (loss) before income taxes and equity in earnings of subsidiaries	(36,572		)	6,870			—			(29,702		)
Benefit from income taxes	10,824			—			—			10,824
Equity in earnings of subsidiaries	6,870			—			(6,870		)	—
Net income (loss)	$	(18,878	)	$	6,870		$	(6,870	)	$	(18,878	)

	Three Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	155,587		$	4,765		$	—		$	160,352
Operating expenses	(158,252		)	(4,611		)	—			(162,863		)
General and administrative	(15,036		)	—			—			(15,036		)
Interest and other income	23,225			—			—			23,225
Income before income taxes and equity in earnings of subsidiaries	5,524			154			—			5,678
Provision for income taxes	(2,380		)	—			—			(2,380		)
Equity in earnings of subsidiaries	154			—			(154		)	—
Net income	$	3,298		$	154		$	(154	)	$	3,298

	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	330,121		$	9,407		$	—		$	339,528
Operating expenses	(281,323		)	(8,823		)	—			(290,146		)
General and administrative	(33,476		)	—			—			(33,476		)
Interest and other income	47,945			—			—			47,945
Income before income taxes and equity in earnings of subsidiaries	63,267			584			—			63,851
Provision for income taxes	(24,660		)	—			—			(24,660		)
Equity in earnings of subsidiaries	584			—			(584		)	—
Net income	$	39,191		$	584		$	(584	)	$	39,191

Schedule of Condensed Consolidating Statements of Comprehensive Income

Condensed Consolidating Statements of Comprehensive Income (Loss)

	Three Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	14,273		$	2,580	$	(2,580	)	$	14,273
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(1,210		)	—		—			(1,210		)
Other comprehensive loss	(1,210		)	—		—			(1,210		)
Comprehensive income	$	13,063		$	2,580	$	(2,580	)	$	13,063
	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income (loss)	$	(18,878	)	$	6,870	$	(6,870	)	$	(18,878	)
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(2,502		)	—		—			(2,502		)
Other comprehensive loss	(2,502		)	—		—			(2,502		)
Comprehensive income (loss)	$	(21,380	)	$	6,870	$	(6,870	)	$	(21,380	)

	Three Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	3,298		$	154	$	(154	)	$	3,298
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(12,997		)	—		—			(12,997		)
Other comprehensive loss	(12,997		)	—		—			(12,997		)
Comprehensive income (loss)	$	(9,699	)	$	154	$	(154	)	$	(9,699	)
	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	39,191		$	584	$	(584	)	$	39,191
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(28,905		)	—		—			(28,905		)
Other comprehensive loss	(28,905		)	—		—			(28,905		)
Comprehensive income	$	10,286		$	584	$	(584	)	$	10,286

Schedule of Condensed Consolidating Statements of Cash Flows

Condensed Consolidating Statements of Cash Flows

	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Cash flows from operating activities	$	112,350		$	10,679		$	—	$	123,029
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(203,397		)	(13,255		)	—		(216,652		)
Additions to furniture, fixtures and other	731			(1,918		)	—		(1,187		)
Proceeds from sale of properties and other investing activities	4,086			—			—		4,086
Cash flows from financing activities:
Proceeds from debt	80,000			—			—		80,000
Principal payments on debt	(4,501		)	—			—		(4,501		)
Intercompany transfers	(4,494		)	4,494			—		—
Other financing activities	(1,345		)	—			—		(1,345		)
Change in cash and cash equivalents	(16,570		)	—			—		(16,570		)
Beginning cash and cash equivalents	79,395			50			—		79,445
Ending cash and cash equivalents	$	62,825		$	50		$	—	$	62,875

	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Cash flows from operating activities	$	175,577		$	3,667		$	—	$	179,244
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(451,421		)	(8,638		)	—		(460,059		)
Additions to furniture, fixtures and other	(4,241		)	—			—		(4,241		)
Proceeds from sale of properties and other investing activities	134			—			—		134
Cash flows from financing activities:
Proceeds from debt	525,000			—			—		525,000
Principal payments on debt	(267,156		)	—			—		(267,156		)
Intercompany transfers	(4,971		)	4,971			—		—
Other financing activities	(9,419		)	—			—		(9,419		)
Change in cash and cash equivalents	(36,497		)	—			—		(36,497		)
Beginning cash and cash equivalents	57,281			50			—		57,331
Ending cash and cash equivalents	$	20,784		$	50		$	—	$	20,834

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Guarantor Subsidiaries - Schedule of Condensed Consolidating Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets:
Current assets	$ 183,224	$ 228,339
Property and equipment, net	2,698,054	2,611,337
Intercompany receivable (payable)	0	0
Investment in subsidiaries	0	0
Noncurrent assets	33,889	29,773
Total Assets	2,915,167	2,869,449
Liabilities and Stockholders’ Equity:
Current liabilities	202,745	213,133
Long-term debt	1,232,864	1,156,654
Deferred income taxes	255,445	266,364
Other noncurrent liabilities	54,291	50,523
Stockholders' equity	1,169,822	1,182,775	1,218,838
Total liabilities and stockholders' equity	2,915,167	2,869,449
Parent Issuer
Assets:
Current assets	180,787	226,013
Property and equipment, net	2,589,265	2,514,240
Intercompany receivable (payable)	146,236	141,272
Investment in subsidiaries	(40,663)	(47,533)
Noncurrent assets	33,889	29,773
Total Assets	2,909,514	2,863,765
Liabilities and Stockholders’ Equity:
Current liabilities	201,900	212,117
Long-term debt	1,232,864	1,156,654
Deferred income taxes	253,194	264,113
Other noncurrent liabilities	51,734	48,106
Stockholders' equity	1,169,822	1,182,775
Total liabilities and stockholders' equity	2,909,514	2,863,765
Guarantor Subsidiaries
Assets:
Current assets	2,437	2,326
Property and equipment, net	108,789	97,097
Intercompany receivable (payable)	(146,236)	(141,272)
Investment in subsidiaries	0	0
Noncurrent assets	0	0
Total Assets	(35,010)	(41,849)
Liabilities and Stockholders’ Equity:
Current liabilities	845	1,016
Long-term debt	0	0
Deferred income taxes	2,251	2,251
Other noncurrent liabilities	2,557	2,417
Stockholders' equity	(40,663)	(47,533)
Total liabilities and stockholders' equity	(35,010)	(41,849)
Intercompany Eliminations
Assets:
Current assets	0	0
Property and equipment, net	0	0
Intercompany receivable (payable)	0	0
Investment in subsidiaries	40,663	47,533
Noncurrent assets	0	0
Total Assets	40,663	47,533
Liabilities and Stockholders’ Equity:
Current liabilities	0	0
Long-term debt	0	0
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Stockholders' equity	40,663	47,533
Total liabilities and stockholders' equity	$ 40,663	$ 47,533

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Guarantor Subsidiaries - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 9.875% Senior Notes	Dec. 31, 2012 9.875% Senior Notes	Jun. 30, 2012 9.875% Senior Notes	Jun. 30, 2013 7.625% Senior Notes	Dec. 31, 2012 7.625% Senior Notes	Jun. 30, 2012 7.625% Senior Notes	Jun. 30, 2013 7.0% Senior Notes	Dec. 31, 2012 7.0% Senior Notes	Jun. 30, 2012 7.0% Senior Notes
Guarantor Subsidiaries [Line Items]
Debt, stated interest rate		9.875%	9.875%	9.875%	7.625%	7.625%	7.625%	7.00%	7.00%	7.00%
Percentage of Guarantor Subsidiaries	100.00%

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Long-Term Debt - Cash and Non-Cash Portion of Interest Expense Related to Long Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Cash interest [Member]
Debt Instrument [Line Items]
Amended Credit Facility interest	$ 1,051	[1]	$ 1,106	[1]	$ 1,915	[1]	$ 2,254	[1]
Non-cash interest [Member]
Debt Instrument [Line Items]
Amended Credit Facility interest	586	[1]	586	[1]	1,171	[1]	1,171	[1]
9.875% Senior Notes | Cash interest [Member]
Debt Instrument [Line Items]
Senior Notes interest	6,172	[2]	6,172	[2]	12,344	[2]	12,344	[2]
9.875% Senior Notes | Non-cash interest [Member]
Debt Instrument [Line Items]
Senior Notes interest	682	[2]	636	[2]	1,361	[2]	1,253	[2]
Convertible Notes | Cash interest [Member]
Debt Instrument [Line Items]
Convertible Notes interest	320	[3]	370	[3]	633	[3]	2,269	[3]
Convertible Notes | Non-cash interest [Member]
Debt Instrument [Line Items]
Convertible Notes interest	1	[3]	1	[3]	3	[3]	1,769	[3]
7.625% Senior Notes | Cash interest [Member]
Debt Instrument [Line Items]
Senior Notes interest	7,625	[4]	7,625	[4]	15,250	[4]	15,250	[4]
7.625% Senior Notes | Non-cash interest [Member]
Debt Instrument [Line Items]
Senior Notes interest	263	[4]	260	[4]	526	[4]	541	[4]
7.0% Senior Notes | Cash interest [Member]
Debt Instrument [Line Items]
Senior Notes interest	7,000	[5]	7,000	[5]	14,000	[5]	8,397	[5]
7.0% Senior Notes | Non-cash interest [Member]
Debt Instrument [Line Items]
Senior Notes interest	194	[5]	201	[5]	389	[5]	267	[5]
Lease Financing Obligation | Cash interest [Member]
Debt Instrument [Line Items]
Financial Obligation interest	768	[6]	0	[6]	1,555	[6]	0	[6]
Lease Financing Obligation | Non-cash interest [Member]
Debt Instrument [Line Items]
Financial Obligation interest	$ 8	[6]	$ 0	[6]	$ 16	[6]	$ 0	[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. See Note 13.

[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.

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Long-Term Debt (Tables)

6 Months Ended

Jun. 30, 2013

Debt Disclosure [Abstract]

Outstanding Debt

The Company’s outstanding debt is summarized below:

		As of June 30, 2013							As of December 31, 2012
	Maturity Date	Principal		Unamortized Discount			Carrying Amount		Principal		Unamortized Discount			Carrying Amount
		(in thousands)
Amended Credit Facility (1)	October 31, 2016	$	80,000	$	—		$	80,000	$	—	$	—		$	—
9.875% Senior Notes (2)	July 15, 2016	250,000		(6,348		)	243,652		250,000		(7,209		)	242,791
Convertible Notes (3)	March 15, 2028 (4)	25,344		—			25,344		25,344		—			25,344
7.625% Senior Notes (5)	October 1, 2019	400,000		—			400,000		400,000		—			400,000
7.0% Senior Notes (6)	October 15, 2022	400,000		—			400,000		400,000		—			400,000
Lease Financing Obligation (7)	August 10, 2020	93,095		—			93,095		97,596		—			97,596
Total Debt		$	1,248,439	$	(6,348	)	$	1,242,091	$	1,172,940	$	(7,209	)	$	1,165,731
Less: Current Portion of Long-Term Debt		9,227		—			9,227		9,077		—			9,077
Total Long-Term Debt		$	1,239,212	$	(6,348	)	$	1,232,864	$	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 approximately $263.1 million and $271.9 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013. See Note 13.

(3) The aggregate estimated fair value of the Convertible Notes was approximately $24.7 million and $25.3 million as of June 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 $417.5 million and $435.0 million as of June 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 $400.0 million and $413.8 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

(7) The aggregate estimated fair value of the Lease Financing Obligation was approximately $90.1 million and $97.7 million as of June 30, 2013 and 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.

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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Amended Credit Facility (1)
Cash interest	$	1,051	$	1,106	$	1,915	$	2,254
Non-cash interest	$	586	$	586	$	1,171	$	1,171
9.875% Senior Notes (2)
Cash interest	$	6,172	$	6,172	$	12,344	$	12,344
Non-cash interest	$	682	$	636	$	1,361	$	1,253
Convertible Notes (3)
Cash interest	$	320	$	370	$	633	$	2,269
Non-cash interest	$	1	$	1	$	3	$	1,769
7.625% Senior Notes (4)
Cash interest	$	7,625	$	7,625	$	15,250	$	15,250
Non-cash interest	$	263	$	260	$	526	$	541
7.0% Senior Notes (5)
Cash interest	$	7,000	$	7,000	$	14,000	$	8,397
Non-cash interest	$	194	$	201	$	389	$	267
Lease Financing Obligation (6)
Cash interest	$	768	$	—	$	1,555	$	—
Non-cash interest	$	8	$	—	$	16	$	—

(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. See Note 13.

(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.

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CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating Activities:
Net Income (Loss)	$ (18,878)	$ 39,191
Adjustments to reconcile to net cash provided by operations:
Depreciation, depletion and amortization	142,745	160,025
Deferred income taxes (benefit)	(10,824)	24,660
Impairment, dry hole costs and abandonment expense	8,283	21,639
Unrealized derivative gain	(762)	(69,052)
Stock compensation and other non-cash charges	9,289	7,640
Amortization of debt discounts and deferred financing costs	3,466	5,002
Gain on sale of properties	(4,193)	0
Change in operating assets and liabilities:
Accounts receivable	16,506	18,136
Prepayments and other assets	1,585	(6,066)
Accounts payable, accrued and other liabilities	(23,743)	(8,853)
Amounts payable to oil and gas property owners	9,737	(5,383)
Production taxes payable	(10,182)	(7,695)
Net cash provided by operating activities	123,029	179,244
Investing Activities:
Additions to oil and gas properties, including acquisitions	(216,652)	(460,059)
Additions of furniture, equipment and other	(1,187)	(4,241)
Proceeds from sale of properties and other investing activities	4,086	134
Net cash used in investing activities	(213,753)	(464,166)
Financing Activities:
Proceeds from debt	80,000	525,000
Principal payments on debt	(4,501)	(267,156)
Proceeds from stock option exercises	3	668
Deferred financing costs and other	(1,348)	(10,087)
Net cash provided by financing activities	74,154	248,425
Decrease in Cash and Cash Equivalents	(16,570)	(36,497)
Beginning Cash and Cash Equivalents	79,445	57,331
Ending Cash and Cash Equivalents	$ 62,875	$ 20,834

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CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Statement of Stockholders' Equity [Abstract]
Effect of derivative financial instruments, taxes	$ 700	$ 7,800	$ 1,503	$ 17,400	$ 30,458

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Supplemental Disclosures of Cash Flow Information

6 Months Ended

Jun. 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:

	Six Months Ended June 30,
	2013			2012
	(in thousands)
Cash paid for interest, net of amount capitalized	$	45,709		$	34,656
Cash paid for income taxes	1,861			8
Supplemental disclosures of non-cash investing and financing activities:
Current liabilities	68,731			75,112
Net increase (decrease) in asset retirement obligations	1,888			(545		)
Retirement of treasury stock	(1,337		)	(2,323		)

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Organization

6 Months Ended

Jun. 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.

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Long-Term Debt - Outstanding Debt (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Debt Instrument [Line Items]
Debt, fair value	$ 1,081.0	$ 1,121.0
9.875% Senior Notes
Debt Instrument [Line Items]
Debt, fair value	263.1	271.9
Debt, stated interest rate	9.875%	9.875%	9.875%
7.625% Senior Notes
Debt Instrument [Line Items]
Debt, fair value	417.5	435.0
Debt, stated interest rate	7.625%	7.625%	7.625%
7.0% Senior Notes
Debt Instrument [Line Items]
Debt, fair value	400.0	413.8
Debt, stated interest rate	7.00%	7.00%	7.00%
Lease Financing Obligation
Debt Instrument [Line Items]
Debt, fair value	90.1	97.7
Convertible Notes
Debt Instrument [Line Items]
Debt, stated interest rate	5.00%
Aggregate fair value of convertible notes	$ 24.7	$ 25.3

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Derivative Instruments (Tables)

6 Months Ended

Jun. 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 June 30, 2013
Balance Sheet	Gross Amounts of Recognized Assets			Gross Amounts Offset in the Balance Sheet				Net Amounts of Assets Presented in the Balance Sheet
				(in thousands)
Derivative assets	$	22,898		$	(3,317	)	(1)	$	19,581
Deferred financing costs and other noncurrent assets	10,274			(483		)	(1)	9,791			(2)
Total derivative assets	$	33,172		$	(3,800	)		$	29,372
Balance Sheet	Gross Amounts of Recognized Liabilities			Gross Amounts Offset in the Balance Sheet				Net Amounts of Liabilities Presented in the Balance Sheet
				(in thousands)
Derivative liabilities	$	(3,373	)	$	3,317		(3)	$	(56	)
Derivatives and other noncurrent liabilities	(483		)	483			(3)	—
Total derivative liabilities	$	(3,856	)	$	3,800			$	(56	)
	As of December 31, 2012
Balance Sheet	Gross Amounts of Recognized Assets			Gross Amounts Offset in the Balance Sheet				Net Amounts of Assets Presented in the Balance 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
Balance Sheet	Gross Amounts of Recognized Liabilities			Gross Amounts Offset in the Balance Sheet				Net Amounts of Liabilities Presented in the Balance 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 June 30, 2013 and December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $24.1 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 and losses, 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 Cash Flow Hedges	Three Months Ended June 30,				Six Months Ended June 30,
		2013		2012		2013		2012
		(in thousands)
Amount of Gain Reclassified from AOCI into Income (net of tax) (1) (2)	Commodity Hedges	$	1,210	$	12,997	$	2,502	$	28,905

(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 $7.8 million for the three months ended June 30, 2013 and 2012, respectively, and $1.5 million and $17.4 million for the six months ended June 30, 2013 and 2012, respectively.

Financial Instruments for Hedging Volumes

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

	July –December 2013	For the year 2014	For the  year 2015
Oil (Bbls)	1,527,200	2,205,400	365,000
Natural Gas (MMbtu)	22,855,000	30,415,000	3,650,000
Natural Gas Liquids (Bbls)	160,714	—	—

Realized and Unrealized Gains and Losses on Commodity Derivative Instruments

The table below summarizes the realized and unrealized gains and losses the Company recognized related to its oil, gas and NGL derivative instruments for the periods indicated:

	Three Months Ended June 30,					Six Months Ended June 30,
	2013			2012		2013		2012
	(in thousands)
Realized gains on derivatives designated as cash flow hedges (1)	$	1,936		$	20,798	$	4,003	$	46,263
Realized gains (losses) on derivatives not designated as cash flow hedges	$	(227	)	$	18,916	$	6,226	$	22,719
Unrealized gains on derivatives not designated as cash flow hedges	37,066			28,108		762		69,052
Total commodity derivative gain (2)	$	36,839		$	47,024	$	6,988	$	91,771

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

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

The table below summarizes the realized gains and losses the Company recognized related to its oil, natural gas and NGL derivative instruments by commodity type for the periods indicated:

	Three Months Ended June 30,					Six Months Ended June 30,
	2013			2012		2013		2012
	(in thousands)
Realized gains on derivatives designated as cash flow hedges
Oil	$	512		$	777	$	913	$	1,546
Gas	1,424			20,021		3,090		44,717
Total (1)	$	1,936		$	20,798	$	4,003	$	46,263
Realized gains (losses) on derivatives not designated as cash flow hedges
Oil	$	2,066		$	3,009	$	4,051	$	1,550
Gas	(3,433		)	12,987		609		16,828
NGL	1,140			2,920		1,566		4,341
Total (2)	$	(227	)	$	18,916	$	6,226	$	22,719

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

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

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Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 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	2,857,757	3,771,662	2,836,480	2,896,452
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

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Summary of Significant Accounting Policies - Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Accounting Policies [Abstract]
Net Income (Loss)	$ 14,273	$ 3,298	$ (18,878)	$ 39,191	$ 582
Basic weighted-average common shares outstanding in period	47,468,569	47,201,954	47,411,054	47,143,430
Add dilutive effects of stock options and nonvested equity shares of common stock	147,000	43,000	0	192,000
Diluted weighted-average common shares outstanding in period	47,615,871	47,245,167	47,411,054	47,334,507
Net Income (Loss) Per Common Share, Basic	$ 0.30	$ 0.07	$ (0.40)	$ 0.83
Net Income (Loss) Per Common Share, Diluted	$ 0.30	$ 0.07	$ (0.40)	$ 0.83

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Equity Incentive Compensation Plans and Other Employee Benefits - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended		1 Months Ended	3 Months Ended	6 Months Ended			1 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended	3 Months Ended	6 Months Ended		1 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Y	Jun. 30, 2012	Dec. 31, 2010	Dec. 31, 2012	Feb. 28, 2013 Performance-Based Awards	Jun. 30, 2012 Two Thousand And Ten Performance Program (2011 Performance)	Jun. 30, 2012 Two Thousand And Ten Performance Program (2011 Performance)	Jun. 30, 2013 Two Thousand And Ten Performance Program (2012 Performance)	Jun. 30, 2012 Two Thousand And Ten Performance Program (2012 Performance)	Feb. 28, 2013 2012 Performance Program	Jun. 30, 2013 2012 Performance Program	Jun. 30, 2012 2012 Performance Program	Jun. 30, 2013 2012 Performance Program	Jun. 30, 2012 2012 Performance Program	Feb. 28, 2013 2012 Performance Program Maximum	Jun. 30, 2013 Two Thousand And Thirteen Performance Program	Jun. 30, 2013 Two Thousand And Thirteen Performance Program	Jun. 30, 2012 Two Thousand And Thirteen Performance Program	Feb. 28, 2013 2010 Performance Program	Feb. 28, 2012 2010 Performance Program	Jun. 30, 2013 Two Thousand And Ten Performance Program (2013 TSR Performance)	Jun. 30, 2013 Two Thousand And Ten Performance Program (2013 TSR Performance)	Jun. 30, 2013 Two Thousand And Ten Performance Program (2013 Performance)	Jun. 30, 2013 Two Thousand And Ten Performance Program (2013 Performance)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 22,500,000		$ 22,500,000
Weighted-average period (years)					2 years 6 months
Supplemental grant percentage of performance based shares	0.00%	26.60%
Non-cash stock based compensation			3,157,000	3,758,000	8,615,000	8,250,000				0	200,000	100,000	200,000		100,000	300,000	100,000	400,000		300,000		400,000			0	0	100,000	200,000
Performance goals percentage weight for stockholder return					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
Performance goals percentage change in discretionary cash flow per debt																			33.33%
Performance goals percentage weight for proved natural gas and oil reserves per debt adjusted share																			33.33%
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%					100.00%
Percentage of total grant that will vest for metrics met at stretch level														200.00%					200.00%
Maximum number of common stock vest as percentage of performance shares granted															200.00%		200.00%
Performance shares set as side at the end of plan																				13,007	287,986
Minimum age for employees to be eligible under employee directed savings plan					21
Percentage of employee's contribution matched by the company					100.00%
Percentage of employee's pretax income					6.00%
Percentage of common stock matched by company					50.00%
Cash and common stock contributions			300,000	400,000	1,200,000	1,200,000
Percentage of employee's cash compensation reached under cash matching contributions							6.00%
Deferred Compensation Liability, Non Current			800,000		800,000			1,000,000
Deferred Compensation Liability, Current			$ 300,000		$ 300,000			$ 300,000

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Derivative Instruments - Cash Flow Hedge Gain and Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Effect of derivative financial instruments, taxes	$ 700		$ 7,800		$ 1,503		$ 17,400		$ 30,458
Commodity Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Qualifying as Cash flow Hedges					Commodity Hedges
Amount of Gain (Loss) Reclassified from AOCI into Income (net of tax)	$ 1,210	[1],[2]	$ 12,997	[1],[2]	$ 2,502	[1],[2]	$ 28,905	[1],[2]

[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 $7.8 million for the three months ended June 30, 2013 and 2012, respectively, and $1.5 million and $17.4 million for the six months ended June 30, 2013 and 2012, respectively.

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Asset Retirement Obligations - Schedule of Asset Retirement Obligations (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
As of December 31, 2012	$ 47,616
Liabilities incurred	1,009
Liabilities settled	(623)
Disposition of properties	(330)
Accretion expense	1,707
Revisions to estimate	1,216
As of June 30, 2013	50,595
Less: current asset retirement obligations	896
Long-term asset retirement obligations	$ 49,699

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CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	48,773,806	48,150,475
Common stock, shares outstanding	48,773,806	48,150,475
Common stock, shares subject to restrictions	1,270,435	870,794
Treasury stock, shares	0	0

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Asset Retirement Obligations

6 Months Ended

Jun. 30, 2013

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

Asset Retirement Obligations

A reconciliation of the Company’s asset retirement obligations for the six months ended June 30, 2013 is as follows (in thousands):

As of December 31, 2012	$	47,616
Liabilities incurred	1,009
Liabilities settled	(623		)
Disposition of properties	(330		)
Accretion expense	1,707
Revisions to estimate	1,216
As of June 30, 2013	$	50,595
Less: current asset retirement obligations	896
Long-term asset retirement obligations	$	49,699

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CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net Income (Loss)	$ 14,273	$ 3,298	$ (18,878)	$ 39,191	$ 582
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(1,210)	(12,997)	(2,502)	(28,905)	(50,712)
Other comprehensive loss	(1,210)	(12,997)	(2,502)	(28,905)
Comprehensive Income (Loss)	$ 13,063	$ (9,699)	$ (21,380)	$ 10,286

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Equity Incentive Compensation Plans and Other Employee Benefits - Director Fees (Detail) (Director, USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Director fees (shares)	3,511	1,657	11,906	3,175
Stock-based compensation (in thousand)	$ 71	$ 36	$ 241	$ 75

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CONSOLIDATED BALANCE SHEETS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 62,875	$ 79,445
Accounts receivable, net of allowance for doubtful accounts	95,457	112,011
Derivative assets	19,581	29,980
Prepayments and other current assets	5,311	6,903
Total current assets	183,224	228,339
Property and equipment - at cost, successful efforts method for oil and gas properties:
Proved oil and gas properties	3,601,215	3,331,267
Unproved oil and gas properties, excluded from amortization	401,217	457,207
Furniture, equipment and other	46,600	45,636
Property, plant and equipment, gross	4,049,032	3,834,110
Accumulated depreciation, depletion, amortization and impairment	(1,350,978)	(1,222,773)
Total property and equipment, net	2,698,054	2,611,337
Deferred financing costs and other noncurrent assets	33,889	29,773
Total Assets	2,915,167	2,869,449
Current liabilities:
Accounts payable and accrued liabilities	120,719	125,017
Amounts payable to oil and gas property owners	25,532	19,663
Production taxes payable	34,866	45,624
Derivative liabilities	56	0
Deferred income taxes	12,345	13,752
Current portion of long-term debt	9,227	9,077
Total current liabilities	202,745	213,133
Long-term debt	1,232,864	1,156,654
Asset retirement obligations	49,699	46,050
Deferred income taxes	255,445	266,364
Derivatives and other noncurrent liabilities	4,592	4,473
Stockholders’ equity:
Common stock, $0.001 par value; authorized 150,000,000 shares; 48,773,806 and 48,150,475 shares issued and outstanding at June 30, 2013 and December 31, 2012, respectively, with 1,270,435 and 870,794 shares subject to restrictions, respectively	48	47
Additional paid-in capital	892,349	883,923
Retained earnings	274,595	293,473
Treasury stock, at cost: zero shares at June 30, 2013 and December 31, 2012, respectively	0	0
Accumulated other comprehensive income	2,830	5,332
Total stockholders’ equity	1,169,822	1,182,775
Total liabilities and stockholders' equity	$ 2,915,167	$ 2,869,449

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Derivative Instruments - Financial Instruments for Hedging Volume (Detail)	Jun. 30, 2013 MMBTU bbl
April-December 2013
Derivative Instruments, Gain (Loss) [Line Items]
Oil (Bbls)	1,527,200
Natural Gas (MMbtu)	22,855,000
Natural Gas Liquids (Bbls)	160,714
2014
Derivative Instruments, Gain (Loss) [Line Items]
Oil (Bbls)	2,205,400
Natural Gas (MMbtu)	30,415,000
Natural Gas Liquids (Bbls)	0
2015
Derivative Instruments, Gain (Loss) [Line Items]
Oil (Bbls)	365,000
Natural Gas (MMbtu)	3,650,000
Natural Gas Liquids (Bbls)	0

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Equity Incentive Compensation Plans and Other Employee Benefits (Tables)

6 Months Ended

Jun. 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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Common stock options	$	727	$	1,573	$	3,217	$	3,673
Nonvested equity common stock	1,588		1,797		3,988		3,774
Nonvested equity common stock units	312		—		712		—
Nonvested performance-based equity	530		388		698		803
Total	$	3,157	$	3,758	$	8,615	$	8,250

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 June 30, 2013			Three Months Ended June 30, 2012
	Number of Options	Weighted Average Price Per Share		Number of Options	Weighted Average Price Per Share
Options to purchase shares of common stock	—	$	—	9,576	$	23.47
	Three Months Ended June 30, 2013			Three Months Ended June 30, 2012
	Number of Shares	Weighted Average Grant Date Fair Value Per Share		Number of Shares	Weighted Average Grant Date Fair Value Per Share
Nonvested equity common stock	16,880	$	19.54	24,617	$	23.54
Nonvested equity common stock units	43,824	$	22.38	—	$	—
Nonvested performance-based equity shares	13,007	$	17.26	4,221	$	23.58
Total shares granted	73,711			28,838

	Six Months Ended June 30, 2013			Six Months Ended June 30, 2012
	Number of Options	Weighted Average Price Per Share		Number of Options	Weighted Average Price Per Share
Options to purchase shares of common stock	—	$	—	555,682	$	27.49
	Six Months Ended June 30, 2013			Six Months Ended June 30, 2012
	Number of Shares	Weighted Average Grant Date Fair Value Per Share		Number of Shares	Weighted Average Grant Date Fair Value Per Share
Nonvested equity common stock	557,260	$	17.32	229,114	$	26.67
Nonvested equity common stock units	52,219	$	22.04	—	$	—
Nonvested performance-based equity shares	287,986	$	16.60	176,587	$	27.65
Total shares granted	897,465			405,701

Directors Fees

A summary of the Company’s directors’ fees and equity-based compensation for the three and six months ended June 30, 2013 and 2012 is presented below:

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
Director fees (shares)	3,511		1,657		11,906		3,175
Stock-based compensation (in thousands)	$	71	$	36	$	241	$	75

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Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2013

Accounting Policies [Abstract]

Summary of Accounts Receivable

Accounts Receivable. Accounts receivable is comprised of the following:

	As of June 30, 2013			As of December 31, 2012
	(in thousands)
Accrued oil, gas and NGL sales	$	61,749		$	69,482
Due from joint interest owners	29,568			36,300
Other	4,163			6,554
Allowance for doubtful accounts	(23		)	(325		)
Total accounts receivable	$	95,457		$	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 June 30, 2013			As of December 31, 2012
	(in thousands)
Proved properties	$	439,312		$	387,242
Wells and related equipment and facilities	2,830,443			2,625,891
Support equipment and facilities	315,910			304,914
Materials and supplies	15,550			13,220
Total proved oil and gas properties	$	3,601,215		$	3,331,267
Unproved properties	322,364			384,486
Wells and facilities in progress	78,853			72,721
Total unproved oil and gas properties, excluded from amortization	$	401,217		$	457,207
Accumulated depreciation, depletion, amortization and impairment	(1,329,493		)	(1,203,495		)
Total oil and gas properties, net	$	2,672,939		$	2,584,979

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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Non-cash impairment of proved oil and gas properties	$	—	$	—	$	—	$	—
Non-cash impairment of unproved oil and gas properties	—		18,337		—		18,337
Dry hole costs	113		42		964		233
Abandonment expense	1,069		2,696		7,319		3,069
Total non-cash impairment, dry hole costs and abandonment expense	$	1,182	$	21,075	$	8,283	$	21,639

Accounts Payable and Accrued Liabilities

Accounts Payable and Accrued Liabilities. Accounts payable and accrued liabilities are comprised of the following:

	As of June 30, 2013		As of December 31, 2012
	(in thousands)
Accrued drilling, completion and facility costs	$	60,572	$	42,094
Accrued lease operating, gathering, transportation and processing expenses	18,393		16,862
Accrued general and administrative expenses	7,530		13,054
Trade payables and other	34,224		53,007
Total accounts payable and accrued liabilities	$	120,719	$	125,017

Calculation of Basic and Diluted Earnings Per Share

The following table sets forth the calculation of basic and diluted earnings per share:

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013			2012
	(in thousands, except per share amounts)
Net income (loss)	$	14,273	$	3,298	$	(18,878	)	$	39,191
Basic weighted-average common shares outstanding in period	47,469		47,202		47,411			47,143
Add dilutive effects of stock options and nonvested equity shares of common stock	147		43		—			192
Diluted weighted-average common shares outstanding in period	47,616		47,245		47,411			47,335
Basic net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83
Diluted net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83

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Long-Term Debt - Cash and Non-Cash Portion of Interest Expense Related to Long Term Debt (Parenthetical) (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 9.875% Senior Notes		Dec. 31, 2012 9.875% Senior Notes		Jun. 30, 2012 9.875% Senior Notes	Jun. 30, 2013 7.625% Senior Notes		Dec. 31, 2012 7.625% Senior Notes		Jun. 30, 2012 7.625% Senior Notes	Jun. 30, 2013 7.0% Senior Notes Due 2022 [Member]	Mar. 12, 2012 7.0% Senior Notes Due 2022 [Member]	Jun. 30, 2013 7.0% Senior Notes		Dec. 31, 2012 7.0% Senior Notes		Jun. 30, 2012 7.0% Senior Notes	Jun. 30, 2013 Lease Financing Obligation		Dec. 31, 2012 Lease Financing Obligation		Jun. 30, 2013 5% Convertible Notes [Member]	Jun. 30, 2012 5% Convertible Notes [Member]
Debt Instrument [Line Items]
Debt, stated interest rate			9.875%		9.875%		9.875%	7.625%		7.625%		7.625%	7.00%		7.00%		7.00%		7.00%					5.00%	5.00%
Effective interest rate of debt instrument			11.20%				11.20%	8.00%				8.00%			7.20%				7.20%	3.30%
Principal amount of debt instrument	$ 1,239,212,000	$ 1,163,863,000	$ 250,000,000	[1]	$ 250,000,000	[1]		$ 400,000,000	[2]	$ 400,000,000	[2]			$ 400,000,000.0	$ 400,000,000	[3]	$ 400,000,000	[3]		$ 93,095,000	[4]	$ 97,596,000	[4]		$ 25,300,000

[1] The aggregate estimated fair value of the 9.875% Senior Notes was approximately $263.1 million and $271.9 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013. See Note 13.

[2] The aggregate estimated fair value of the 7.625% Senior Notes was approximately $417.5 million and $435.0 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

[3] The aggregate estimated fair value of the 7.0% Senior Notes was approximately $400.0 million and $413.8 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

[4] The aggregate estimated fair value of the Lease Financing Obligation was approximately $90.1 million and $97.7 million as of June 30, 2013 and 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.

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Equity Incentive Compensation Plans and Other Employee Benefits - Non-Cash Stock-Based Compensation Cost Related to Equity Awards (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Stock Based Compensation [Line Items]
Non-cash stock-based compensation equity awards	$ 3,157,000	$ 3,758,000	$ 8,615,000	$ 8,250,000
Common Stock Options
Stock Based Compensation [Line Items]
Non-cash stock-based compensation equity awards	727,000	1,573,000	3,217,000	3,673,000
Nonvested Equity Common Stock
Stock Based Compensation [Line Items]
Non-cash stock-based compensation equity awards	1,588,000	1,797,000	3,988,000	3,774,000
Nonvested Equity Common Stock Units
Stock Based Compensation [Line Items]
Non-cash stock-based compensation equity awards	312,000	0	712,000	0
Nonvested Performance-Based Equity
Stock Based Compensation [Line Items]
Non-cash stock-based compensation equity awards	$ 530,000	$ 388,000	$ 698,000	$ 803,000

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Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues	$ 142,299	$ 160,352	$ 280,576	$ 339,528
Operating expenses	(118,295)	(162,863)	(234,214)	(290,146)
General and administrative	(13,273)	(15,036)	(33,855)	(33,476)
Interest and other income (expense)	12,145	23,225	(42,209)	47,945
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	22,876	5,678	(29,702)	63,851
Provision for (Benefit from) Income Taxes	(8,603)	(2,380)	10,824	(24,660)
Equity in earnings (loss) of subsidiaries	0	0	0	0
Net Income (Loss)	14,273	3,298	(18,878)	39,191	582
Parent Issuer
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues	135,631	155,587	265,771	330,121
Operating expenses	(114,207)	(158,252)	(226,279)	(281,323)
General and administrative	(13,273)	(15,036)	(33,855)	(33,476)
Interest and other income (expense)	12,145	23,225	(42,209)	47,945
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	20,296	5,524	(36,572)	63,267
Provision for (Benefit from) Income Taxes	(8,603)	(2,380)	10,824	(24,660)
Equity in earnings (loss) of subsidiaries	2,580	154	6,870	584
Net Income (Loss)	14,273	3,298	(18,878)	39,191
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues	6,668	4,765	14,805	9,407
Operating expenses	(4,088)	(4,611)	(7,935)	(8,823)
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	2,580	154	6,870	584
Provision for (Benefit from) Income Taxes	0	0	0	0
Equity in earnings (loss) of subsidiaries	0	0	0	0
Net Income (Loss)	2,580	154	6,870	584
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	(2,580)	(154)	(6,870)	(584)
Net Income (Loss)	$ (2,580)	$ (154)	$ (6,870)	$ (584)

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Divestitures - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Cash proceeds and recognized	$ 325.3
Cash proceeds and recognized pre-tax loss	$ 4.5
Wind River Basin
Percentage of natural gas assets sold	100.00%
Powder River Basin
Percentage of natural gas assets sold	100.00%

XML

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 $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Summary Of Significant Accounting Policies [Line Items]
Dry hole costs	$ 113	$ 42	$ 964	$ 233
Abandonment expense	1,069	2,696	7,319	3,069
Total non-cash impairment, dry hole costs and abandonment expense	1,182	21,075	8,283	21,639
Proved Oil and Gas Properties
Summary Of Significant Accounting Policies [Line Items]
Non-cash impairment of oil and gas properties	0	0	0	0
Unproved Oil and Gas Properties
Summary Of Significant Accounting Policies [Line Items]
Non-cash impairment of oil and gas properties	$ 0	$ 18,337	$ 0	$ 18,337

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Summary of Significant Accounting Policies - Accounts Payable and Accrued Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Accrued drilling, completion and facility costs	$ 60,572	$ 42,094
Accrued lease operating, gathering, transportation and processing expenses	18,393	16,862
Accrued general and administrative expenses	7,530	13,054
Trade payables and other	34,224	53,007
Total accounts payable and accrued liabilities	$ 120,719	$ 125,017

XML

Long-Term Debt

6 Months Ended

Jun. 30, 2013

Debt Disclosure [Abstract]

Long-Term Debt

Long-Term Debt

The Company’s outstanding debt is summarized below:

		As of June 30, 2013							As of December 31, 2012
	Maturity Date	Principal		Unamortized Discount			Carrying Amount		Principal		Unamortized Discount			Carrying Amount
		(in thousands)
Amended Credit Facility (1)	October 31, 2016	$	80,000	$	—		$	80,000	$	—	$	—		$	—
9.875% Senior Notes (2)	July 15, 2016	250,000		(6,348		)	243,652		250,000		(7,209		)	242,791
Convertible Notes (3)	March 15, 2028 (4)	25,344		—			25,344		25,344		—			25,344
7.625% Senior Notes (5)	October 1, 2019	400,000		—			400,000		400,000		—			400,000
7.0% Senior Notes (6)	October 15, 2022	400,000		—			400,000		400,000		—			400,000
Lease Financing Obligation (7)	August 10, 2020	93,095		—			93,095		97,596		—			97,596
Total Debt		$	1,248,439	$	(6,348	)	$	1,242,091	$	1,172,940	$	(7,209	)	$	1,165,731
Less: Current Portion of Long-Term Debt		9,227		—			9,227		9,077		—			9,077
Total Long-Term Debt		$	1,239,212	$	(6,348	)	$	1,232,864	$	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 approximately $263.1 million and $271.9 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013. See Note 13.

(3) The aggregate estimated fair value of the Convertible Notes was approximately $24.7 million and $25.3 million as of June 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 $417.5 million and $435.0 million as of June 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 $400.0 million and $413.8 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

(7) The aggregate estimated fair value of the Lease Financing Obligation was approximately $90.1 million and $97.7 million as of June 30, 2013 and 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.

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 1.7% for the three months ended June 30, 2013 and 2012, and 1.7% and 1.8% for the six months ended June 30, 2013 and 2012, respectively.

The borrowing base is required to be re-determined twice per year. The borrowing base was re-affirmed at $825.0 million as of April 24, 2013 related to its normal spring re-determination. 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 June 30, 2013, the Company had $80.0 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, effective May 4, 2010, which reduces the current borrowing capacity of the Amended Credit Facility to $719.0 million.

9.875% Senior Notes Due 2016

On July 8, 2009, the Company issued $250.0 million in aggregate principal amount of 9.875% Senior Notes due 2016 at 95.172% of par resulting in a discount of $12.1 million. The 9.875% Senior Notes were scheduled to mature on July 15, 2016. On June 14, 2013, the Company delivered a notice of redemption to the holders of the 9.875% Senior Notes announcing that the Company elected, pursuant to the indenture for the notes, to redeem the entire outstanding $250.0 million principal amount of the notes on July 15, 2013 for a redemption price of 104.938% of the principal amount of the notes. The Company redeemed the 9.875% Senior Notes in full on July 15, 2013. See Note 13 for additional information regarding the redemption of the 9.875% Senior Notes.

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 9.875% Senior Notes, 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, 9.875% Senior 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, the 9.875% Senior 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 beginning October 15, 2012. 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, 9.875% Senior 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, the 9.875% Senior Notes and the 7.625% Senior Notes. The 7.0% Senior Notes include certain covenants that limit the Company’s ability to incur additional indebtedness, make restricted payments, create liens or sell assets and that prohibit the Company from paying dividends. The Company is currently in compliance with all financial covenants and has complied with all financial covenants since issuance.

Lease Financing Obligation Due 2020

On July 23, 2012, the Company entered into a lease financing arrangement with Bank of America Leasing & Capital, LLC as the lead bank (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.

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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Amended Credit Facility (1)
Cash interest	$	1,051	$	1,106	$	1,915	$	2,254
Non-cash interest	$	586	$	586	$	1,171	$	1,171
9.875% Senior Notes (2)
Cash interest	$	6,172	$	6,172	$	12,344	$	12,344
Non-cash interest	$	682	$	636	$	1,361	$	1,253
Convertible Notes (3)
Cash interest	$	320	$	370	$	633	$	2,269
Non-cash interest	$	1	$	1	$	3	$	1,769
7.625% Senior Notes (4)
Cash interest	$	7,625	$	7,625	$	15,250	$	15,250
Non-cash interest	$	263	$	260	$	526	$	541
7.0% Senior Notes (5)
Cash interest	$	7,000	$	7,000	$	14,000	$	8,397
Non-cash interest	$	194	$	201	$	389	$	267
Lease Financing Obligation (6)
Cash interest	$	768	$	—	$	1,555	$	—
Non-cash interest	$	8	$	—	$	16	$	—

(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. See Note 13.

(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.

XML

Commitments and Contingencies - Future Minimum Annual Payments under Drilling, Lease and Other Agreements (Detail) (Office & Equipment Leases, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Office & Equipment Leases
Operating Leased Assets [Line Items]
2013	$ 2,118
2014	3,625
2015	2,995
2016	2,519
2017	2,481
Thereafter	3,154
Total	$ 16,892

XML

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2013

Commitments and Contingencies Disclosure [Abstract]

Schedule of Aggregate Undiscounted Minimum Future Lease Payments

Lease Financing Obligation. The Company has a Lease Financing Obligation with Bank of America Leasing & Capital, LLC as the lead bank as discussed in Note 5. The aggregate undiscounted minimum future lease payments are presented below:

	As of June 30, 2013
	(in thousands)
2013	$	6,069
2014	12,139
2015	12,139
2016	12,139
2017	12,139
Thereafter	32,368
Total	$	86,993

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 June 30, 2013
	(in thousands)
2013	$	28,900
2014	57,929
2015	58,065
2016	56,464
2017	51,824
Thereafter	140,726
Total	$	393,908

Future Minimum Annual Payments Under Drilling, Lease and Other Agreements

Future minimum annual payments under lease and other agreements are as follows:

	As of June 30, 2013
	(in thousands)
2013	$	2,118
2014	3,625
2015	2,995
2016	2,519
2017	2,481
Thereafter	3,154
Total	$	16,892

XML

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

3 Months Ended

6 Months Ended

6 Months Ended

1 Months Ended

6 Months Ended

6 Months Ended

6 Months Ended

6 Months Ended

6 Months Ended

1 Months Ended

6 Months Ended

6 Months Ended

6 Months Ended

Jun. 30, 2013

Jun. 30, 2012

Jun. 30, 2013

Jun. 30, 2012

Dec. 31, 2012

Jun. 30, 2013

Minimum

Jun. 30, 2013

Maximum

Mar. 20, 2012

5% Convertible Senior Notes Due 2028

Jun. 30, 2013

5% Convertible Senior Notes Due 2028

Mar. 12, 2008

5% Convertible Senior Notes Due 2028

Jun. 30, 2013

Convertible Notes

Jun. 30, 2013

Amended Credit Facility

Dec. 31, 2012

Amended Credit Facility

Jun. 30, 2013

9.875% Senior Notes Due 2016

Jul. 08, 2009

9.875% Senior Notes Due 2016

Jun. 30, 2013

9.875% Senior Notes

Dec. 31, 2012

9.875% Senior Notes

Jun. 30, 2012

9.875% Senior Notes

Jun. 30, 2013

7.625% Senior Notes Due 2019 [Member]

Sep. 27, 2011

7.625% Senior Notes Due 2019 [Member]

Jun. 30, 2013

7.0% Senior Notes Due 2022 [Member]

Mar. 12, 2012

7.0% Senior Notes Due 2022 [Member]

Jul. 23, 2012

Lease Financing Obligation

Jun. 30, 2013

Lease Financing Obligation

Dec. 31, 2012

Lease Financing Obligation

Jun. 30, 2013

7.625% Senior Notes

Dec. 31, 2012

7.625% Senior Notes

Jun. 30, 2012

7.625% Senior Notes

Jun. 30, 2013

7.0% Senior Notes

Dec. 31, 2012

7.0% Senior Notes

Jun. 30, 2012

7.0% Senior Notes

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 825,000,000.0

$ 825,000,000.0

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

Mar. 15, 2028

Oct. 31, 2016

^[1]

Jul. 15, 2016

Jul. 15, 2016

^[2]

Oct. 01, 2019

Oct. 15, 2022

Aug. 10, 2020

^[3]

Oct. 01, 2019

^[4]

Oct. 15, 2022

^[5]

Commitment fee percentage

0.375%

0.50%

Average annual interest rates incurred on Amended Credit Facility

1.70%

1.70%

1.70%

1.80%

Borrowing base determination

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

Line of credit facility, maximum amount outstanding during period

80,000,000

Letters of credit issued amount

26,000,000.0

Line of credit facility, reduced borrowing capacity

719,000,000

Principal amount

1,239,212,000

1,239,212,000

1,163,863,000

172,500,000.0

25,300,000

80,000,000

^[1]

0

^[1]

250,000,000.0

250,000,000

^[2]

250,000,000

^[2]

400,000,000.0

400,000,000.0

93,095,000

^[3]

97,596,000

^[3]

400,000,000

^[4]

400,000,000

^[4]

400,000,000

^[5]

400,000,000

^[5]

Debt instrument, issuance at par, percentage

95.172%

Debt discount

6,348,000

6,348,000

7,209,000

0

^[1]

0

^[1]

12,100,000

6,348,000

^[2]

7,209,000

^[2]

0

^[3]

0

^[3]

0

^[4]

0

^[4]

0

^[5]

0

^[5]

Par value of senior notes

104.938%

103.813%

103.50%

Face Amount of Outstanding Convertible Notes Repaid

147,200,000

Percentage of notes put to company

85.00%

Debt, stated interest rate

5.00%

5.00%

9.875%

9.875%

9.875%

7.625%

7.00%

7.625%

7.625%

7.625%

7.00%

7.00%

7.00%

Debt instrument conversion price rate of redemption

100.00%

Minimum days notice to call Convertible Notes

30 days

Sale and subsequent lease back

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 approximately $263.1 million and $271.9 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments. The 9.875% Senior Notes were redeemed in full on July 15, 2013. See Note 13.

[3] The aggregate estimated fair value of the Lease Financing Obligation was approximately $90.1 million and $97.7 million as of June 30, 2013 and 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.

[4] The aggregate estimated fair value of the 7.625% Senior Notes was approximately $417.5 million and $435.0 million as of June 30, 2013 and December 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 $400.0 million and $413.8 million as of June 30, 2013 and December 31, 2012, respectively, based on reported market trades of these instruments.

XML

Derivative Instruments

6 Months Ended

Jun. 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 June 30, 2013
Balance Sheet	Gross Amounts of Recognized Assets			Gross Amounts Offset in the Balance Sheet				Net Amounts of Assets Presented in the Balance Sheet
				(in thousands)
Derivative assets	$	22,898		$	(3,317	)	(1)	$	19,581
Deferred financing costs and other noncurrent assets	10,274			(483		)	(1)	9,791			(2)
Total derivative assets	$	33,172		$	(3,800	)		$	29,372
Balance Sheet	Gross Amounts of Recognized Liabilities			Gross Amounts Offset in the Balance Sheet				Net Amounts of Liabilities Presented in the Balance Sheet
				(in thousands)
Derivative liabilities	$	(3,373	)	$	3,317		(3)	$	(56	)
Derivatives and other noncurrent liabilities	(483		)	483			(3)	—
Total derivative liabilities	$	(3,856	)	$	3,800			$	(56	)
	As of December 31, 2012
Balance Sheet	Gross Amounts of Recognized Assets			Gross Amounts Offset in the Balance Sheet				Net Amounts of Assets Presented in the Balance 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
Balance Sheet	Gross Amounts of Recognized Liabilities			Gross Amounts Offset in the Balance Sheet				Net Amounts of Liabilities Presented in the Balance 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 June 30, 2013 and December 31, 2012, this line item on the Unaudited Consolidated Balance Sheets includes $24.1 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 and losses, 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 Cash Flow Hedges	Three Months Ended June 30,				Six Months Ended June 30,
		2013		2012		2013		2012
		(in thousands)
Amount of Gain Reclassified from AOCI into Income (net of tax) (1) (2)	Commodity Hedges	$	1,210	$	12,997	$	2,502	$	28,905

(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 $7.8 million for the three months ended June 30, 2013 and 2012, respectively, and $1.5 million and $17.4 million for the six months ended June 30, 2013 and 2012, respectively.

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

	July –December 2013	For the year 2014	For the  year 2015
Oil (Bbls)	1,527,200	2,205,400	365,000
Natural Gas (MMbtu)	22,855,000	30,415,000	3,650,000
Natural Gas Liquids (Bbls)	160,714	—	—

The table below summarizes the realized and unrealized gains and losses the Company recognized related to its oil, gas and NGL derivative instruments for the periods indicated:

	Three Months Ended June 30,					Six Months Ended June 30,
	2013			2012		2013		2012
	(in thousands)
Realized gains on derivatives designated as cash flow hedges (1)	$	1,936		$	20,798	$	4,003	$	46,263
Realized gains (losses) on derivatives not designated as cash flow hedges	$	(227	)	$	18,916	$	6,226	$	22,719
Unrealized gains on derivatives not designated as cash flow hedges	37,066			28,108		762		69,052
Total commodity derivative gain (2)	$	36,839		$	47,024	$	6,988	$	91,771

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

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

The table below summarizes the realized gains and losses the Company recognized related to its oil, natural gas and NGL derivative instruments by commodity type for the periods indicated:

	Three Months Ended June 30,					Six Months Ended June 30,
	2013			2012		2013		2012
	(in thousands)
Realized gains on derivatives designated as cash flow hedges
Oil	$	512		$	777	$	913	$	1,546
Gas	1,424			20,021		3,090		44,717
Total (1)	$	1,936		$	20,798	$	4,003	$	46,263
Realized gains (losses) on derivatives not designated as cash flow hedges
Oil	$	2,066		$	3,009	$	4,051	$	1,550
Gas	(3,433		)	12,987		609		16,828
NGL	1,140			2,920		1,566		4,341
Total (2)	$	(227	)	$	18,916	$	6,226	$	22,719

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

(2) Included in commodity derivative gain 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 June 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.

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Divestitures

6 Months Ended

Jun. 30, 2013

Discontinued Operations and Disposal Groups [Abstract]

Divestitures

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 “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 Divestiture proceeds are subject to various purchase price adjustments incurred in the normal course of business and will be finalized during 2013.

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CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) (USD $) 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	(1,334)	1	2	0	(1,337)	0
Stock-based compensation	9,761	0	9,761	0	0	0
Retirement of treasury stock	0	0	(1,337)	0	1,337	0
Net Income (Loss)	(18,878)	0	0	(18,878)	0	0
Effect of derivative financial instruments, net of taxes	(2,502)	0	0	0	0	(2,502)
Balance at Jun. 30, 2013	$ 1,169,822	$ 48	$ 892,349	$ 274,595	$ 0	$ 2,830

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Derivative Instruments - Realized and Unrealized Gains and Losses on Commodity Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivatives not designated as cash flow hedges					$ 762		$ 69,052
Oil hedge
Derivative Instruments, Gain (Loss) [Line Items]
Realized gains on derivatives designated as cash flow hedge	512		777		913		1,546
Realized gains on derivatives not designated as cash flow hedges	2,066		3,009		4,051		1,550
Natural gas hedge
Derivative Instruments, Gain (Loss) [Line Items]
Realized gains on derivatives designated as cash flow hedge	1,424		20,021		3,090		44,717
Realized gains on derivatives not designated as cash flow hedges	(3,433)		12,987		609		16,828
NGL hedge
Derivative Instruments, Gain (Loss) [Line Items]
Realized gains on derivatives not designated as cash flow hedges	1,140		2,920		1,566		4,341
Oil and Natural Gas Derivative Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Realized gains on derivatives designated as cash flow hedge	1,936	[1]	20,798	[1]	4,003	[1]	46,263	[1]
Realized gains on derivatives not designated as cash flow hedges	(227)	[2]	18,916	[2]	6,226	[2]	22,719	[2]
Unrealized gains (losses) on derivatives not designated as cash flow hedges	37,066		28,108		762		69,052
Total commodity derivative gain (loss)	$ 36,839	[2]	$ 47,024	[2]	$ 6,988	[2]	$ 91,771	[2]

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

[2] Included in commodity derivative gain in the Unaudited Consolidated Statements of Operations.

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Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Fair Value Measurements [Line Items]
Debt, fair value	$ 1,081.0	$ 1,121.0
9.875% Senior Notes
Fair Value Measurements [Line Items]
Debt, stated interest rate	9.875%	9.875%	9.875%
Debt, fair value	263.1	271.9
7.625% Senior Notes
Fair Value Measurements [Line Items]
Debt, stated interest rate	7.625%	7.625%	7.625%
Debt, fair value	417.5	435.0
7.0% Senior Notes
Fair Value Measurements [Line Items]
Debt, stated interest rate	7.00%	7.00%	7.00%
Debt, fair value	400.0	413.8
Amended Credit Facility
Fair Value Measurements [Line Items]
Debt, fair value	80.0
Convertible Notes
Fair Value Measurements [Line Items]
Debt, fair value	24.7	25.3
Lease Financing Obligation
Fair Value Measurements [Line Items]
Debt, fair value	$ 90.1	$ 97.7

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Summary of Significant Accounting Policies - Summary of Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts	$ (23)	$ (325)
Accounts receivable	95,457	112,011
Accrued Oil, Gas, and NGL Sales
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	61,749	69,482
Due from Joint Interest Owners
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	29,568	36,300
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	$ 4,163	$ 6,554

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Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net Income (Loss)	$ 14,273	$ 3,298	$ (18,878)	$ 39,191	$ 582
Effect of derivative financial instruments	(1,210)	(12,997)	(2,502)	(28,905)	(50,712)
Other comprehensive loss	(1,210)	(12,997)	(2,502)	(28,905)
Comprehensive Income (Loss)	13,063	(9,699)	(21,380)	10,286
Parent Issuer
Condensed Financial Statements, Captions [Line Items]
Net Income (Loss)	14,273	3,298	(18,878)	39,191
Effect of derivative financial instruments	(1,210)	(12,997)	(2,502)	(28,905)
Other comprehensive loss	(1,210)	(12,997)	(2,502)	(28,905)
Comprehensive Income (Loss)	13,063	(9,699)	(21,380)	10,286
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Income (Loss)	2,580	154	6,870	584
Effect of derivative financial instruments	0	0	0	0
Other comprehensive loss	0	0	0	0
Comprehensive Income (Loss)	2,580	154	6,870	584
Intercompany Eliminations
Condensed Financial Statements, Captions [Line Items]
Net Income (Loss)	(2,580)	(154)	(6,870)	(584)
Effect of derivative financial instruments	0	0	0	0
Other comprehensive loss	0	0	0	0
Comprehensive Income (Loss)	$ (2,580)	$ (154)	$ (6,870)	$ (584)

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Commitments and Contingencies - Schedule of Aggregate Undiscounted Minimum Future Lease Payments (Detail) (Lease Financing Obligation, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Lease Financing Obligation
Future Minimum Lease Payments Under Capital Leases And Operating Leases For Continuing Operations [Line Items]
2013	$ 6,069
2014	12,139
2015	12,139
2016	12,139
2017	12,139
Thereafter	32,368
Total	$ 86,993

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Commitments and Contingencies

6 Months Ended

Jun. 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 June 30, 2013
	(in thousands)
2013	$	6,069
2014	12,139
2015	12,139
2016	12,139
2017	12,139
Thereafter	32,368
Total	$	86,993

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 11 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 $18.0 million of transportation demand charges for the three and six months ended June 30, 2013, respectively. The Company paid $1.4 million and $2.0 million of firm processing charges for the three and six months ended June 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 $11.1 million and $22.3 million of transportation demand charges for the three and six months ended June 30, 2012, respectively. The Company paid $1.6 million and $3.1 million of firm processing charges for the three and six months ended June 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 June 30, 2013
	(in thousands)
2013	$	28,900
2014	57,929
2015	58,065
2016	56,464
2017	51,824
Thereafter	140,726
Total	$	393,908

Drilling, Lease and Other Commitments. At June 30, 2013, the Company had one drilling commitment through 2014, which requires the Company to drill two wells before October 31, 2014. If the Company does not drill the two wells, it is required to pay a contracted amount of $1.3 million. The Company also 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 $1.0 million for both the three and six months ended June 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 June 30, 2013
	(in thousands)
2013	$	2,118
2014	3,625
2015	2,995
2016	2,519
2017	2,481
Thereafter	3,154
Total	$	16,892

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 financial position, cash flows or results of operations.

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Fair Value Measurements

6 Months Ended

Jun. 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 June 30, 2013
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Deferred Compensation Plan	$	824	$	—	$	—	$	824
Cash Equivalents - Money Market Funds	8,562		—		—		8,562
Commodity Derivatives	—		33,172		—		33,172
Liabilities
Commodity Derivatives	$	—	$	3,856	$	—	$	3,856

	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 value of the Company’s fixed rate 9.875% Senior Notes, 7.625% Senior Notes and 7.0% Senior Notes was $1,081.0 million and $1,121.0 million as of June 30, 2013 and December 30, 2012, respectively, and is 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 $80.0 million as of June 30, 2013 approximates its fair value due to its floating rate structure. The Convertible Notes fair value of $24.7 million and $25.3 million as of June 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 value of $90.1 million and $97.7 million as of June 30, 2013 and December 31, 2012, respectively, is 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 June 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. The inputs used to determine such fair value are primarily based upon internally developed cash flow models and would generally be classified within Level 3. The Company also applied fair value accounting guidance to measure the assets and liabilities in the Divestiture in 2012. 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 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.

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Subsequent Events (Details) (USD $)	3 Months Ended		6 Months Ended			6 Months Ended		0 Months Ended			0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 9.875% Senior Notes Due 2016	Jul. 08, 2009 9.875% Senior Notes Due 2016	Jul. 12, 2013 Subsequent Event	Jul. 12, 2013 Subsequent Event 9.875% Senior Notes Due 2016	Jun. 14, 2013 Subsequent Event 9.875% Senior Notes Due 2016	Jul. 12, 2013 Subsequent Event Amended Credit Facility
Subsequent Event [Line Items]
Debt, stated interest rate										9.875%
Debt Instrument, Face Amount	$ 1,239,212,000		$ 1,239,212,000		$ 1,163,863,000		$ 250,000,000.0			$ 250,000,000
Par value of senior notes						104.938%			104.938%
Proceeds from long-term lines of credit											280,000,000
Repayments of long-term debt									262,300,000
Interest paid									12,300,000
Loss on extinguishment of debt	$ 0	$ 0	$ 0	$ (1,601,000)				$ 21,400,000

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Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 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 June 30, 2013			As of December 31, 2012
	(in thousands)
Accrued oil, gas and NGL sales	$	61,749		$	69,482
Due from joint interest owners	29,568			36,300
Other	4,163			6,554
Allowance for doubtful accounts	(23		)	(325		)
Total accounts receivable	$	95,457		$	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 June 30, 2013			As of December 31, 2012
	(in thousands)
Proved properties	$	439,312		$	387,242
Wells and related equipment and facilities	2,830,443			2,625,891
Support equipment and facilities	315,910			304,914
Materials and supplies	15,550			13,220
Total proved oil and gas properties	$	3,601,215		$	3,331,267
Unproved properties	322,364			384,486
Wells and facilities in progress	78,853			72,721
Total unproved oil and gas properties, excluded from amortization	$	401,217		$	457,207
Accumulated depreciation, depletion, amortization and impairment	(1,329,493		)	(1,203,495		)
Total oil and gas properties, net	$	2,672,939		$	2,584,979

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 June 30, 2013, 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 June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
	(in thousands)
Non-cash impairment of proved oil and gas properties	$	—	$	—	$	—	$	—
Non-cash impairment of unproved oil and gas properties	—		18,337		—		18,337
Dry hole costs	113		42		964		233
Abandonment expense	1,069		2,696		7,319		3,069
Total non-cash impairment, dry hole costs and abandonment expense	$	1,182	$	21,075	$	8,283	$	21,639

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 June 30, 2013		As of December 31, 2012
	(in thousands)
Accrued drilling, completion and facility costs	$	60,572	$	42,094
Accrued lease operating, gathering, transportation and processing expenses	18,393		16,862
Accrued general and administrative expenses	7,530		13,054
Trade payables and other	34,224		53,007
Total accounts payable and accrued liabilities	$	120,719	$	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 June 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 Per Share. Basic net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding during each period. Diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common stock by the weighted average number of common shares outstanding and other dilutive securities. Potentially dilutive securities for the diluted net income (loss) 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.

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 June 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 income (loss) per common share calculation for the three and six months ended June 30, 2013 and 2012. The diluted net income (loss) per common share excludes the anti-dilutive effect of 2,857,757 and 3,771,662 shares of stock options and nonvested performance-based shares of common stock for the three months ended June 30, 2013 and 2012, respectively, and 2,836,480 and 2,896,452 shares of stock options and nonvested performance-based shares of common stock for the six months ended June 30, 2013 and 2012, respectively.

The following table sets forth the calculation of basic and diluted earnings per share:

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013			2012
	(in thousands, except per share amounts)
Net income (loss)	$	14,273	$	3,298	$	(18,878	)	$	39,191
Basic weighted-average common shares outstanding in period	47,469		47,202		47,411			47,143
Add dilutive effects of stock options and nonvested equity shares of common stock	147		43		—			192
Diluted weighted-average common shares outstanding in period	47,616		47,245		47,411			47,335
Basic net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83
Diluted net income (loss) per common share	$	0.30	$	0.07	$	(0.40	)	$	0.83

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 Update 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 FASB 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.

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Guarantor Subsidiaries

6 Months Ended

Jun. 30, 2013

Text Block [Abstract]

Guarantor Subsidiaries

Guarantor Subsidiaries

In addition to the Amended Credit Facility, 9.875% Senior Notes, 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 June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Assets:
Current assets	$	180,787		$	2,437		$	—	$	183,224
Property and equipment, net	2,589,265			108,789			—		2,698,054
Intercompany receivable (payable)	146,236			(146,236		)	—		—
Investment in subsidiaries	(40,663		)	—			40,663		—
Noncurrent assets	33,889			—			—		33,889
Total assets	$	2,909,514		$	(35,010	)	$	40,663	$	2,915,167
Liabilities and Stockholders’ Equity:
Current liabilities	$	201,900		$	845		$	—	$	202,745
Long-term debt	1,232,864			—			—		1,232,864
Deferred income taxes	253,194			2,251			—		255,445
Other noncurrent liabilities	51,734			2,557			—		54,291
Stockholders’ equity	1,169,822			(40,663		)	40,663		1,169,822
Total liabilities and stockholders’ equity	$	2,909,514		$	(35,010	)	$	40,663	$	2,915,167

	As of December 31, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(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 June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	135,631		$	6,668		$	—		$	142,299
Operating expenses	(114,207		)	(4,088		)	—			(118,295		)
General and administrative	(13,273		)	—			—			(13,273		)
Interest income and other income	12,145			—			—			12,145
Income before income taxes and equity in earnings of subsidiaries	20,296			2,580			—			22,876
Provision for income taxes	(8,603		)	—			—			(8,603		)
Equity in earnings of subsidiaries	2,580			—			(2,580		)	—
Net income	$	14,273		$	2,580		$	(2,580	)	$	14,273

	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	265,771		$	14,805		$	—		$	280,576
Operating expenses	(226,279		)	(7,935		)	—			(234,214		)
General and administrative	(33,855		)	—			—			(33,855		)
Interest income and other income (expense)	(42,209		)	—			—			(42,209		)
Income (loss) before income taxes and equity in earnings of subsidiaries	(36,572		)	6,870			—			(29,702		)
Benefit from income taxes	10,824			—			—			10,824
Equity in earnings of subsidiaries	6,870			—			(6,870		)	—
Net income (loss)	$	(18,878	)	$	6,870		$	(6,870	)	$	(18,878	)

	Three Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	155,587		$	4,765		$	—		$	160,352
Operating expenses	(158,252		)	(4,611		)	—			(162,863		)
General and administrative	(15,036		)	—			—			(15,036		)
Interest and other income	23,225			—			—			23,225
Income before income taxes and equity in earnings of subsidiaries	5,524			154			—			5,678
Provision for income taxes	(2,380		)	—			—			(2,380		)
Equity in earnings of subsidiaries	154			—			(154		)	—
Net income	$	3,298		$	154		$	(154	)	$	3,298

	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations			Consolidated
	(in thousands)
Operating and other revenues	$	330,121		$	9,407		$	—		$	339,528
Operating expenses	(281,323		)	(8,823		)	—			(290,146		)
General and administrative	(33,476		)	—			—			(33,476		)
Interest and other income	47,945			—			—			47,945
Income before income taxes and equity in earnings of subsidiaries	63,267			584			—			63,851
Provision for income taxes	(24,660		)	—			—			(24,660		)
Equity in earnings of subsidiaries	584			—			(584		)	—
Net income	$	39,191		$	584		$	(584	)	$	39,191

Condensed Consolidating Statements of Comprehensive Income (Loss)

	Three Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	14,273		$	2,580	$	(2,580	)	$	14,273
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(1,210		)	—		—			(1,210		)
Other comprehensive loss	(1,210		)	—		—			(1,210		)
Comprehensive income	$	13,063		$	2,580	$	(2,580	)	$	13,063
	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income (loss)	$	(18,878	)	$	6,870	$	(6,870	)	$	(18,878	)
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(2,502		)	—		—			(2,502		)
Other comprehensive loss	(2,502		)	—		—			(2,502		)
Comprehensive income (loss)	$	(21,380	)	$	6,870	$	(6,870	)	$	(21,380	)

	Three Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	3,298		$	154	$	(154	)	$	3,298
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(12,997		)	—		—			(12,997		)
Other comprehensive loss	(12,997		)	—		—			(12,997		)
Comprehensive income (loss)	$	(9,699	)	$	154	$	(154	)	$	(9,699	)
	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries		Intercompany Eliminations			Consolidated
	(in thousands)
Net income	$	39,191		$	584	$	(584	)	$	39,191
Other Comprehensive Loss, net of tax:
Effect of derivative financial instruments	(28,905		)	—		—			(28,905		)
Other comprehensive loss	(28,905		)	—		—			(28,905		)
Comprehensive income	$	10,286		$	584	$	(584	)	$	10,286

Condensed Consolidating Statements of Cash Flows

	Six Months Ended June 30, 2013
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Cash flows from operating activities	$	112,350		$	10,679		$	—	$	123,029
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(203,397		)	(13,255		)	—		(216,652		)
Additions to furniture, fixtures and other	731			(1,918		)	—		(1,187		)
Proceeds from sale of properties and other investing activities	4,086			—			—		4,086
Cash flows from financing activities:
Proceeds from debt	80,000			—			—		80,000
Principal payments on debt	(4,501		)	—			—		(4,501		)
Intercompany transfers	(4,494		)	4,494			—		—
Other financing activities	(1,345		)	—			—		(1,345		)
Change in cash and cash equivalents	(16,570		)	—			—		(16,570		)
Beginning cash and cash equivalents	79,395			50			—		79,445
Ending cash and cash equivalents	$	62,825		$	50		$	—	$	62,875

	Six Months Ended June 30, 2012
	Parent Issuer			Guarantor Subsidiaries			Intercompany Eliminations		Consolidated
	(in thousands)
Cash flows from operating activities	$	175,577		$	3,667		$	—	$	179,244
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(451,421		)	(8,638		)	—		(460,059		)
Additions to furniture, fixtures and other	(4,241		)	—			—		(4,241		)
Proceeds from sale of properties and other investing activities	134			—			—		134
Cash flows from financing activities:
Proceeds from debt	525,000			—			—		525,000
Principal payments on debt	(267,156		)	—			—		(267,156		)
Intercompany transfers	(4,971		)	4,971			—		—
Other financing activities	(9,419		)	—			—		(9,419		)
Change in cash and cash equivalents	(36,497		)	—			—		(36,497		)
Beginning cash and cash equivalents	57,281			50			—		57,331
Ending cash and cash equivalents	$	20,784		$	50		$	—	$	20,834

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Document and Entity Information	6 Months Ended
	Jun. 30, 2013	Jul. 19, 2013
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q2
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		48,711,632

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Subsequent Events

6 Months Ended

Jun. 30, 2013

Subsequent Events [Abstract]

Subsequent Events

Subsequent Events

On June 14, 2013, the Company delivered a notice of redemption to the holders of its 9.875% Senior Notes announcing that, pursuant to the indenture for the notes, the Company elected to redeem the entire outstanding $250.0 million principal amount of the notes on July 15, 2013 for a redemption price of 104.938% of the principal amount of the notes. The Company drew down $280.0 million on its revolving credit facility on July 12, 2013 to fund the redemption of the notes for $262.3 million as well as make the final semi-annual interest payment of $12.3 million. At the redemption date there were unamortized debt discount and deferred financing costs related to the notes resulting in a loss upon settlement of $21.4 million, which will be recorded in the quarter ended September 30, 2013.

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Commitments and Contingencies - Gross Future Minimum Transportation Demand and Firm Processing Charges (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
2013	$ 28,900
2014	57,929
2015	58,065
2016	56,464
2017	51,824
Thereafter	140,726
Total	$ 393,908

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Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013 well	Jun. 30, 2012	Jun. 30, 2013 Agreement well	Jun. 30, 2012
Contingencies And Commitments [Line Items]
Transportation Demand Charges	$ 9.5	$ 11.1	$ 18.0	$ 22.3
Firm processing charges	1.4	1.6	2.0	3.1
Future minimum drilling commitment	1.3		1.3
Number of wells associated with drilling commitment	2		2
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			$ 0.5	$ 1.0
2013 Drilling Contract
Contingencies And Commitments [Line Items]
Number of oil rigs	1		1
Minimum
Contingencies And Commitments [Line Items]
Contract term, years	2 years		2 years
Maximum
Contingencies And Commitments [Line Items]
Contract term, years	11 years		11 years