SM Energy (SM) 10-Q 30 Apr 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	3 Months Ended
	Mar. 31, 2014	Apr. 23, 2014
Entity Information [Line Items]	'	'
Entity Registrant Name	'SM Energy Co	'
Entity Central Index Key	'0000893538	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	67,058,145
Entity Current Reporting Status	'Yes	'

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (in thousands, except share amounts) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets	'	'
Cash and cash equivalents	$236,435	$282,248
Accounts receivable	307,784	318,371
Derivative asset	7,450	21,559
Deferred income taxes	11,227	10,749
Prepaid expense and other	14,446	14,574
Total current assets	577,342	647,501
Proved oil and gas properties	5,875,541	5,637,462
Less - accumulated depletion, depreciation, and amortization	-2,722,287	-2,583,698
Unproved oil and gas properties	287,607	271,100
Wells in progress	277,879	279,654
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	42,276	19,072
Other property and equipment, net of accumulated depreciation of $31,013 in 2014 and $28,775 in 2013	243,680	236,202
Total property and equipment, net	4,004,696	3,859,792
Derivative asset	13,886	30,951
Restricted cash	23,753	96,713
Other noncurrent assets	69,334	70,208
Total other noncurrent assets	106,973	197,872
Total Assets	4,689,011	4,705,165
Liabilities	'	'
Accounts payable and accrued expenses	443,395	606,751
Derivative liability	60,684	26,380
Other current liabilities	11,200	6,000
Total current liabilities	515,279	639,131
Revolving credit facility	0	0
Senior Notes (note 5)	1,600,000	1,600,000
Asset retirement obligation	115,889	115,659
Asset retirement obligation associated with oil and gas properties held for sale	4,526	3,033
Net Profits Plan liability	55,209	56,985
Deferred income taxes	688,994	650,125
Derivatives liability	7,885	4,640
Other noncurrent liabilities	25,810	28,771
Total noncurrent liabilities	2,498,313	2,459,213
Commitments and contingencies (note 6)	'	'
Stockholders' equity:	'	'
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 67,078,853 shares in 2014 and 67,078,853 shares in 2013; outstanding, net of treasury shares: 67,056,441 shares in 2014 and 67,056,441 shares in 2013	671	671
Additional paid-in-capital	264,064	257,720
Treasury stock, at cost: 22,412 shares in 2014 and 22,412 in 2013	-823	-823
Retained earnings	1,416,923	1,354,669
Accumulated other comprehensive loss	-5,416	-5,416
Total stockholders' equity	1,675,419	1,606,821
Total Liabilities and Stockholders' Equity	$4,689,011	$4,705,165

Balance_Sheet_Parenthetical_Pa

Balance Sheet Parenthetical (Parentheticals) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$2,722,287	$2,583,698
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	67,078,853	67,078,853
Common Stock, Shares, Outstanding	67,056,441	67,056,441
Treasury Stock, Shares	22,412	22,412
Assets Held-for-sale [Member]	'	'
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	31,776	7,390
Other Capitalized Property Plant and Equipment [Member]	'	'
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$31,013	$28,775

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) (in thousands, except per share amounts) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Operating revenues:	'		'
Oil, gas, and NGL production revenue	$623,109		$469,575
Other operating revenues	9,611		14,605
Total operating revenues	632,720		484,180
Operating expenses:	'		'
Oil, gas, and NGL production expense	163,709		125,633
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	177,215		198,709
Exploration	21,335		15,398
Impairment of properties	2,801		21,521
General and administrative	35,051		32,280
Change in Net Profits Plan liability	-1,776		-1,925
Derivative loss	-97,662	[1]	-30,572	[1]
Other operating expense	8,089		15,794
Total operating expenses	504,086		437,982
Income from operations	128,634		46,198
Non-operating income (expense)	'		'
Interest income	26		12
Interest expense	-24,190		-19,101
Income before income taxes	104,470		27,109
Income tax expense	-38,863		-10,382
Net income	$65,607		$16,727
Basic weighted-average common shares outstanding	67,056		66,211
Diluted weighted-average common shares outstanding	68,126		67,521
Basic net income per common share	$0.98		$0.25
Diluted net income per common share	$0.96		$0.25
Dividends per common share	$0.05		$0.05
[1]	(2)B Total derivative loss is reported in the derivative loss line item on the condensed consolidated statements of cash flows within cash provided by operating activities.

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Statement of Comprehensive Income [Abstract]	'		'
Net income	$65,607		$16,727
Reclassification to earnings	0	[1]	61	[1]
Pension liability adjustment	0		-3
Total other comprehensive income, net of tax	0		58
Total comprehensive income	$65,607		$16,785
[1]	Reclassification from accumulated other comprehensive income (loss) (bAOCILb) related to de-designated hedges. As of December 31, 2013, all commodity derivative contracts that had been designated as cash flow hedges were settled and reclassified into earnings from AOCIL.

CONDENSED_CONSOLIDATED_STATEME2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Statement of Cash Flows [Abstract]	'		'
Net income	$65,607		$16,727
Adjustments to reconcile net income to net cash provided by operating activities:	'		'
(Gain) loss on divestiture activity	2,958		-574
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	177,215		198,709
Exploratory dry hole expense	0		159
Impairment of properties	2,801		21,521
Stock-based compensation expense	6,344		8,113
Change in Net Profits Plan liability	-1,776		-1,925
Derivative loss	97,662	[1]	30,572	[1]
Derivative cash settlement (loss) gain	-28,940	[2]	11,792	[2]
Amortization of debt discount and deferred financing costs	1,477		1,077
Deferred income taxes	38,374		10,280
Plugging and abandonment	-1,325		-1,378
Other	-3,103		1,836
Changes in current assets and liabilities:	'		'
Accounts receivable	9,347		-22,164
Prepaid expenses and other	885		605
Accounts payable and accrued expenses	-61,882		5,794
Net Cash Provided by Operating Activities	299,728		282,292
Cash flows from investing activities:	'		'
Net proceeds from sale of oil and gas properties	1,979		4,307
Capital expenditures	-351,739		-381,185
Other	4,227		-2,025
Net cash used in investing activities	-345,533		-378,903
Cash flows from financing activities:	'		'
Proceeds from credit facility	0		223,500
Repayment of credit facility	0		-133,500
Other	-8		772
Net cash provided by (used in) financing activities	-8		90,772
Net change in cash and cash equivalents	-45,813		-5,839
Cash and cash equivalents at beginning of period	282,248		5,926
Cash and cash equivalents at ending of period	236,435		87
Supplemental schedule of additional cash flow information and noncash investing and financing activities:	'		'
Cash paid for interest, net of capitalized interest	-37,851		-24,721
Net cash refunded for income taxes	14		165
Assets Held for Sale	'		'
Assets Held-for-sale Reasonably Certain Period for Sale	1		'
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	42,276		'
Asset retirement obligation associated with oil and gas properties held for sale	$4,526		'
[1]	(2)B Total derivative loss is reported in the derivative loss line item on the condensed consolidated statements of cash flows within cash provided by operating activities.
[2]	(1)B Total derivative cash settlement loss (gain) is reported in the derivative cash settlement (loss) gain line item on the condensed consolidated statements of cash flows within net cash provided by operating activities.

CONDENSED_CONSOLIDATED_STATEME3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (in thousands) (Parenthetical) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Statement of Cash Flows [Abstract]	'	'
Dividends, Common Stock	$3.40	$3.30
Capital expenditures incurred but not yet paid	$200.50	$202.80

The_Company_and_Business

The Company and Business	3 Months Ended
	Mar. 31, 2014
Company and Business Disclosure [Abstract]	'
The Company and Business	'
	Note 1 - The Company and Business
	SM Energy Company (“SM Energy” or the “Company”) is an independent energy company engaged in the acquisition, exploration, development, and production of crude oil and condensate, natural gas, and natural gas liquids (also respectively referred to as “oil,” “gas,” and “NGLs” throughout this report) in onshore North America, with a current focus on oil and liquids-rich resource plays.

Basis_of_Presentation_Signific

Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards	'
	Note 2 - Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements of SM Energy have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and the instructions to Form 10-Q and Regulation S-X. They do not include all information and notes required by GAAP for complete financial statements. However, except as disclosed herein, there has been no material change in the information disclosed in the notes to consolidated financial statements included in SM Energy’s Annual Report on Form 10-K for the year ended December 31, 2013 (the “2013 Form 10-K”). In the opinion of management, all adjustments, consisting of normal recurring accruals considered necessary for a fair presentation of interim financial information, have been included. Operating results for the periods presented are not necessarily indicative of expected results for the full year. In connection with the preparation of its unaudited condensed consolidated financial statements, the Company evaluated events subsequent to the balance sheet date of March 31, 2014, through the filing date of this report.
	Significant Accounting Policies
	The significant accounting policies followed by the Company are set forth in Note 1 to the Company’s consolidated financial statements in its 2013 Form 10-K, and are supplemented by the notes to the unaudited condensed consolidated financial statements in this report. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the 2013 Form 10-K.
	Recently Issued Accounting Standards
	In April 2014, the Financial Accounting Standards Board issued new authoritative accounting guidance related to the recognition and presentation of discontinued operations in the financial statements. The guidance is aimed at reducing the frequency of disposals reported as discontinued operations by focusing on strategic shifts that have or will have a major effect on an entity’s operations and financial results. This authoritative accounting guidance is effective for interim and annual periods beginning after December 15, 2014, and is to be applied prospectively. The Company is currently evaluating the provisions of this authoritative guidance and assessing its impact, but does not currently believe it will have a material effect on the Company's financial statements or disclosures.
	There are no other new significant accounting standards applicable to the Company that have been issued but not yet adopted by the Company as of March 31, 2014.

Assets_Held_for_Sale_Assets_He

Assets Held for Sale Assets Held for Sale	3 Months Ended
	Mar. 31, 2014
Assets held for sale [Abstract]	'
Assets Held-for-sale	'
	Note 3 – Acquisitions, Divestitures, and Assets Held for Sale
	Acquisitions
	Subsequent to March 31, 2014, the Company entered into separate agreements to acquire acreage in its Rocky Mountain region for total cash consideration of approximately $100.0 million plus approximately 7,000 net acres. These agreements are expected to close during the second quarter 2014 and are subject to standard closing conditions and normal closing and post-closing adjustments. No assurance can be given that the Company will successfully close any of these acquisitions.
	Assets Held for Sale
	Assets are classified as held for sale when the Company commits to a plan to sell the assets and there is reasonable certainty the sale will take place within one year. Upon classification as held for sale, long-lived assets are no longer depreciated or depleted, and a measurement for impairment is performed to identify and expense any excess of carrying value over fair value less estimated costs to sell. Subsequent decreases to the estimated fair value less the costs to sell will impact the measurement of assets held for sale.
	As of March 31, 2014, the accompanying condensed consolidated balance sheets (“accompanying balance sheets”) present $42.3 million of oil and gas properties held for sale, net of accumulated depletion, depreciation, and amortization expense. A corresponding asset retirement obligation liability of $4.5 million is separately presented. The assets held for sale include the Company’s Marcellus shale assets located in Pennsylvania and other non-strategic assets in the Company’s Rocky Mountain region, all of which are recorded at the lesser of their carrying values or their respective fair value less estimated costs to sell. When write-downs to fair value less estimated costs to sell occur, they are reflected in gain (loss) on divestiture activity, which is included within the other operating revenues line item in the accompanying condensed consolidated statements of operations (“accompanying statements of operations”).
	The Company determined that these planned asset sales do not qualify for discontinued operations accounting under financial statement presentation authoritative guidance.

Earnings_per_Share

Earnings per Share	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings per Share	'
	Note 9 - Earnings per Share
	Basic net income per common share is calculated by dividing net income available to common stockholders by the basic weighted-average common shares outstanding for the respective period. The Company’s earnings per share calculations reflect the impact of any repurchases of shares of common stock made by the Company.
	Diluted net income per common share is calculated by dividing adjusted net income by the diluted weighted-average common shares outstanding, which includes the effect of potentially dilutive securities. Potentially dilutive securities for this calculation consist of in-the-money outstanding stock options, unvested RSUs, and contingent PSUs. The treasury stock method is used to measure the dilutive impact of unvested RSUs, contingent PSUs, and in-the-money stock options.
	PSUs represent the right to receive, upon settlement of the PSUs after completion of the three-year performance period, a number of shares of the Company’s common stock that may range from 0% to 200% of the number of PSUs granted on the award date. The number of potentially dilutive shares related to PSUs is based on the number of shares, if any, that would be issuable at the end of the respective reporting period, assuming that date was the end of the contingency period applicable to such PSUs. For additional discussion on PSUs, please refer to Note 7 - Compensation Plans under the heading Performance Stock Units Under the Equity Incentive Compensation Plan.
	The following table sets forth the calculations of basic and diluted earnings per share:
		For the Three Months Ended March 31,
		2014		2013
		(in thousands, except per share amounts)
	Net income	$	65,607	$	16,727
	Basic weighted-average common shares outstanding	67,056		66,211
	Add: dilutive effect of stock options, unvested RSUs, and contingent PSUs	1,070		1,310
	Diluted weighted-average common shares outstanding	68,126		67,521
	Basic net income per common share	$	0.98	$	0.25
	Diluted net income per common share	$	0.96	$	0.25

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Note 4 - Income Taxes
	Income tax expense for the three months ended March 31, 2014, and 2013, differs from the amounts that would be provided by applying the statutory United States federal income tax rate to income before income taxes primarily due to the effect of state income taxes, changes in valuation allowances, percentage depletion, research and development (“R&D”) credits, and other permanent differences. The quarterly rate can also be impacted by the proportional effects of forecasted net income as of each period end presented.
	The provision for income taxes consists of the following:
		For the Three Months Ended March 31,
		2014			2013
		(in thousands)
	Current portion of income tax expense:
	Federal	$	—		$	—
	State	489			102
	Deferred portion of income tax expense	38,374			10,280
	Total income tax expense	$	38,863		$	10,382
		37.2		%	38.3		%
	On a year-to-date basis, a change in the Company’s effective tax rate between reported periods will generally reflect differences in its estimated highest marginal state tax rate due to changes in the composition of income from Company activities among various state tax jurisdictions. Cumulative effects of state rate changes are reflected in the period legislation is enacted. The decrease in the effective rate from 2013 primarily reflects temporary and permanent changes in the mix of highest marginal state tax rates, the effects of valuation allowance adjustments, the state tax rate effect divestitures have between years, drilling activities, and changes in the effects of other permanent differences.
	The Company and its subsidiaries file federal income tax returns and various state income tax returns. With certain exceptions, the Company is no longer subject to United States federal or state income tax examinations by tax authorities for years before 2007. Federal tax law allowing for the calculation of an R&D credit was enacted in 2013, which allowed the credit for the 2012 and 2013 tax years. However, the Company has not yet commissioned a study to calculate the credit for these tax years. The table above excludes the impact for any credit that would be allowed in 2013. The Internal Revenue Service (“IRS”) initiated an audit in the first quarter of 2012 related to R&D tax credits claimed by the Company for the 2007 through 2010 tax years. On April 23, 2013, the IRS issued a Notice of Proposed Adjustment disallowing $4.6 million of R&D tax credits claimed for open tax years during the audit period. The Company maintains it is entitled to the claimed credits and is pursuing its appeal.
	On September 13, 2013, the United States Department of the Treasury and IRS issued the final and re-proposed tangible property regulations effective for tax years beginning January 1, 2014. The Company has determined it is materially compliant with the requirements of these regulations.

LongTerm_Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Long-term debt	'
	Note 5 - Long-term Debt
	Revolving Credit Facility
	The Company’s Fifth Amended and Restated Credit Agreement provides a maximum loan amount of $2.5 billion, current aggregate lender commitments of $1.3 billion, and a maturity date of April 12, 2018.  The borrowing base is subject to regular semi-annual redeterminations and was re-affirmed on March 28, 2014, at $2.2 billion. The borrowing base redetermination process under the credit facility considers the value of the Company’s oil and gas properties and other assets, as determined by the lender group. The next scheduled redetermination date is October 1, 2014. Borrowings under the facility are secured by at least 75 percent of the Company’s proved oil and gas properties.
	The Company must comply with certain financial and non-financial covenants under the terms of its credit facility agreement, including the limitation of the Company’s dividends to no more than $50.0 million per year.  The Company was in compliance with all covenants under the credit facility as of March 31, 2014, and through the filing date of this report.
	The following table presents the outstanding balance, total amount of letters of credit, and available borrowing capacity under the Company’s credit facility as of April 23, 2014, March 31, 2014, and December 31, 2013:
		As of April 23, 2014		As of March 31, 2014		As of December 31, 2013
		(in thousands)
	Credit facility balance	$	—	$	—	$	—
	Letters of credit (1)	$	808	$	808	$	808
	Available borrowing capacity	$	1,299,192	$	1,299,192	$	1,299,192
	____________________________________________
	(1) Letters of credit reduce the available borrowing capacity under the credit facility on a dollar-for-dollar basis.
	Senior Notes
	The Senior Notes line on the accompanying balance sheets represents the outstanding principal amount of the 6.625% Senior Notes due 2019 (the “2019 Notes”), the 6.50% Senior Notes due 2021 (the “2021 Notes”), the 6.50% Senior Notes due 2023 (the “2023 Notes”), and the 5.0% Senior Notes due 2024 (the “2024 Notes” and collectively with the 2019 Notes, 2021 Notes, and 2023 Notes, the “Senior Notes”), as shown in the table below:
		As of March 31, 2014		As of December 31, 2013
		(in thousands)
	2019 Notes	$	350,000	$	350,000
	2021 Notes	350,000		350,000
	2023 Notes	400,000		400,000
	2024 Notes	500,000		500,000
	Total Senior Notes	$	1,600,000	$	1,600,000
	The Senior Notes are unsecured senior obligations and rank equal in right of payment with all of the Company’s existing and any future unsecured senior debt, and are senior in right of payment to any future subordinated debt. There are no subsidiary guarantors of the Senior Notes.  The Company is subject to certain covenants under the respective indentures governing the Senior Notes that limit the Company’s ability to incur additional indebtedness, issue preferred stock, and make restricted payments, including dividends; provided, however, that the first $6.5 million of dividends paid each year are not restricted by these covenants. The Company was in compliance with all covenants under its Senior Notes as of March 31, 2014, and through the filing date of this report.
	5.0% Senior Notes Due 2024
	On May 20, 2013, the Company issued $500.0 million in aggregate principal amount of 2024 Notes. The 2024 Notes were issued at par and mature on January 15, 2024. Please refer to Note 5 - Long-term Debt in the Company’s 2013 Form 10-K for additional discussion of the terms of these notes.
	On May 20, 2013, the Company entered into a registration rights agreement that provides holders of the 2024 Notes certain registration rights under the Securities Act of 1933, as amended (the “Securities Act”). Pursuant to the registration rights agreement, the Company filed an exchange offer registration statement with the Securities and Exchange Commission (“SEC”) on March 4, 2014, offering to exchange the 2024 Notes for substantially identical notes that are registered under the Securities Act. If the registration statement is not declared effective by the SEC on or before May 20, 2014, or if the shelf registration statement, if required, is not declared effective within the time periods specified in the registration rights agreement, the Company has agreed to pay additional interest with respect to the 2024 Notes in an amount not to exceed one percent of the principal amount of the 2024 Notes until the exchange offer is completed or the shelf registration statement is declared effective.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Note 6 - Commitments and Contingencies
	Commitments
	During the first quarter of 2014, and through the filing date of this report, the Company entered into drilling rig contracts with varying terms extending through 2016. The total commitments for these contracts is $52.7 million.
	Contingencies
	The Company is subject to litigation and claims arising in the ordinary course of business. The Company accrues for such items when a liability is both probable and the amount can be reasonably estimated. In the opinion of management, the results of such pending litigation and claims will not have a material effect on the results of operations, the financial position, or the cash flows of the Company.
	On April 16, 2014, the Company agreed to settle its previously disclosed litigation against Endeavour Operating Corporation (“Endeavour”). The Company, its working interest partners, and Endeavour agreed to release all claims and dismiss the lawsuit in exchange for certain cash payments and other consideration paid to the Company and its working interest partners by Endeavour.
	On January 27, 2011, Chieftain Royalty Company (“Chieftain”) filed a Class Action Petition against the Company in the District Court of Beaver County, Oklahoma, claiming damages related to royalty valuation on all of the Company’s Oklahoma wells. These claims include breach of contract, breach of fiduciary duty, fraud, unjust enrichment, tortious breach of contract, conspiracy, and conversion, based generally on asserted improper deduction of post-production costs. The Company removed this lawsuit to the United States District Court for the Western District of Oklahoma on February 22, 2011. The Company responded to the petition and denied the allegations. The district court did not rule on Chieftain’s motion to certify the putative class, and stayed all proceedings until the United States Court of Appeals for the Tenth Circuit issued its rulings on class certification in two similar royalty class action lawsuits. On July 9, 2013, the Tenth Circuit issued its opinions, reversing the trial courts’ grant of class certification and remanding the matters to the trial courts for those cases. The district court presiding over the Company’s case subsequently lifted its stay, and the Company expects Chieftain to file a new motion for class certification in the first half of 2015.
	This case involves complex legal issues and uncertainties; a potentially large class of plaintiffs, and a large number of related producing properties, lease agreements and wells; and an alleged class period commencing in 1988 and spanning the entire producing life of the wells. Because the proceedings are in the early stages, with discovery yet to be completed, the Company is unable to estimate what impact, if any, the action will have on its financial condition, results of operations, or cash flows. The Company is still evaluating the claims, but believes that it has properly paid royalties under Oklahoma law and has and will continue to vigorously defend this case. On December 30, 2013, the Company sold a substantial portion of the assets that are subject to this matter and the buyer assumed any such liabilities related to such properties.

Compensation_Plans

Compensation Plans	3 Months Ended
	Mar. 31, 2014
Compensation Related Costs [Abstract]	'
Compensation Plans	'
	Note 7 - Compensation Plans
	Cash Bonus Plan
	During the first quarters of 2014 and 2013, the Company paid $41.7 million and $16.0 million, respectively, for cash bonuses earned during the 2013 and 2012 performance years, respectively. The general and administrative (“G&A”) expense and exploration expense line items in the accompanying statements of operations include $6.6 million and $5.6 million of accrued cash bonus plan expense for the three months ended March 31, 2014, and 2013, respectively, related to the respective performance years.
	Non-qualified Deferred Compensation Plan
	In January 2014, the Company established a non-qualified deferred compensation (“NQDC”) plan intended to provide plan participants with the ability to plan for income tax events and the opportunity to receive a benefit for matching contributions in excess of Internal Revenue Code (“IRC”) limits applicable to the Company’s 401(k) plan. The NQDC plan is designed to allow participants to defer a portion of base salary and cash bonuses paid pursuant to the Company’s cash bonus plan. Each year, participating employees may elect to defer (i) between 0% and 50% of their base salary, and (ii) between 0% and 100% of the cash bonus paid pursuant to the cash bonus plan. The NQDC plan requires the Company to make contributions for each eligible employee equal to 100% of the deferred amount for such employee, limited to 6% of such employee’s base salary and cash bonus. Each eligible employee’s interest in the contributions the Company makes will vest 40% after the second year of such employee’s service to the Company, and 20% per year thereafter. A participant’s account will be distributed based upon the participant’s payment election made at the time of deferral. A participant may elect to have distributions made in lump sum or in annual installments ranging for a period from 1 to 10 years. Participants in the NQDC plan are currently limited to the Company’s officers and directors.
	Restricted Stock Units Under the Equity Incentive Compensation Plan
	The Company grants restricted stock units (“RSUs”) as part of its equity compensation program. Each RSU represents a right to one share of the Company’s common stock to be delivered upon settlement of the award at the end of the specified vesting period. Expense associated with RSUs is recognized as G&A expense and exploration expense over the vesting period of the award.
	Total expense recorded for RSUs for the three months ended March 31, 2014, and 2013, was $2.8 million and $3.0 million, respectively. As of March 31, 2014, there was $15.9 million of total unrecognized compensation expense related to unvested RSU awards, which is being amortized through 2016. There have been no material changes to the outstanding and non-vested RSUs during the three months ended March 31, 2014.
	Performance Stock Units Under the Equity Incentive Compensation Plan
	The Company grants performance share units (“PSUs”) as part of its equity compensation program. The number of shares of the Company’s common stock issued to settle PSUs ranges from 0% to 200% of the number of PSUs awarded and is determined based on the Company’s performance over a three-year measurement period. The performance criteria for the PSUs are based on a combination of the Company’s annualized total shareholder return (“TSR”) for the measurement period and the relative measure of the Company’s TSR compared with the annualized TSRs of a group of peer companies for the measurement period. Expense associated with PSUs is recognized as G&A expense and exploration expense over the vesting period of the award.
	Total expense recorded for PSUs for the three months ended March 31, 2014, and 2013, was $3.2 million and $4.7 million, respectively. As of March 31, 2014, there was $14.9 million of total unrecognized compensation expense related to unvested PSU awards, which is being amortized through 2016. There have been no material changes to the outstanding and non-vested PSUs during the three months ended March 31, 2014.
	Stock Option Grants Under the Equity Incentive Compensation Plan
	As of March 31, 2014, there were 39,088 stock option awards outstanding at a weighted average exercise price of $20.87 with an aggregate intrinsic value of $2.0 million. There was no unrecognized compensation expense as of March 31, 2014, and no changes in these awards occurred during the quarter.
	Net Profits Interest Bonus Plan
	Cash payments made or accrued under the Company’s Net Profits Interest Bonus Plan (“Net Profits Plan”) that have been recorded as either G&A expense or exploration expense are presented in the table below:
		For the Three Months Ended March 31,
		2014		2013
		(in thousands)
	General and administrative expense	$	2,978	$	3,786
	Exploration expense	288		374
	Total	$	3,266	$	4,160
	The Company records changes in the present value of estimated future payments under the Net Profits Plan as a separate line item in the accompanying statements of operations. The change in the estimated liability is recorded as a non-cash expense or benefit in the current period and is not allocated to G&A expense or exploration expense because it is associated with the future net cash flows from oil and gas properties in the respective pools rather than results being realized through current period production. If the Company allocated the change in liability to these specific functional line items, based on the current allocation of actual distributions made by the Company, such expenses or benefits would predominately be allocated to G&A expense. Over time, less of the amount distributed relates to prospective exploration efforts as more of the amount distributed is paid to employees that have terminated employment and do not provide ongoing exploration support to the Company.

Pension_Benefits

Pension Benefits	3 Months Ended
	Mar. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]	'
Pension Benefits	'
	Note 8 - Pension Benefits
	Pension Plans
	The Company has a non-contributory pension plan covering substantially all employees who meet age and service requirements (the “Qualified Pension Plan”). The Company also has a supplemental non-contributory pension plan covering certain management employees (the “Nonqualified Pension Plan” and together with the Qualified Pension Plan, the “Pension Plans”).
	Components of Net Periodic Benefit Cost for the Pension Plans
	The following table presents the components of the net periodic benefit cost for the Pension Plans:
		For the Three Months Ended March 31,
		2014			2013
		(in thousands)
	Service cost	$	1,573		$	1,232
	Interest cost	407			345
	Expected return on plan assets that reduces periodic pension costs	(385		)	(286		)
	Amortization of prior service costs	4			4
	Amortization of net actuarial loss	306			197
	Net periodic benefit cost	$	1,905		$	1,492
	Prior service costs are amortized on a straight-line basis over the average remaining service period of active participants. Gains and losses in excess of 10 percent of the greater of the benefit obligation and the market-related value of assets are amortized over the average remaining service period of active participants.
	Contributions
	The Company contributed $5.3 million to the Pension Plans during the three month period ended March 31, 2014.

Derivative_Financial_Instrumen

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Financial Instruments	'
	Note 10 - Derivative Financial Instruments
	Summary of Oil, Gas, and NGL Derivative Contracts in Place
	The Company has entered into various commodity derivative contracts to mitigate a portion of its exposure to potentially adverse market changes in commodity prices and the associated impact on cash flows. All contracts are entered into for other-than-trading purposes. The Company’s derivative contracts include swap and costless collar arrangements for oil, gas, and NGLs.
	As of March 31, 2014, and through the filing date of this report, the Company has commodity derivative contracts outstanding through the second quarter of 2018 for a total of 17.0 million Bbls of oil production, 216.6 million MMBtu of gas production, and 2.9 million Bbls of NGL production.
	In a typical commodity swap agreement, if the agreed upon published third-party index price is lower than the swap fixed price, the Company receives the difference between the index price and the agreed upon swap fixed price. If the index price is higher than the swap fixed price, the Company pays the difference.  For collar agreements, the Company receives the difference between an agreed upon index and the floor price if the index price is below the floor price.  The Company pays the difference between the agreed upon ceiling price and the index price if the index price is above the ceiling price.  No amounts are paid or received if the index price is between the floor and ceiling prices.
	The following tables summarize the approximate volumes and average contract prices of contracts the Company had in place as of March 31, 2014, and through the filing date of this report:
	Oil Contracts
	Oil Swaps
	Contract Period		NYMEX WTI Volumes			Weighted-Average
						Contract Price
			(Bbls)			(per Bbl)
	Second quarter 2014		2,373,000			$	94.95
	Third quarter 2014		1,533,000			$	96.04
	Fourth quarter 2014		1,353,000			$	94.88
	2015		3,308,000			$	89.34
	2016		2,704,000			$	85.19
	All oil swaps		11,271,000
	Oil Collars
	Contract Period		NYMEX WTI			Weighted-				Weighted-
			Volumes			Average Floor				Average Ceiling
						Price				Price
			(Bbls)			(per Bbl)				(per Bbl)
	Second quarter 2014		431,000			$	85			$	102.5
	Third quarter 2014		973,000			$	85			$	102.58
	Fourth quarter 2014		923,000			$	85			$	102.63
	2015		3,366,000			$	85			$	94.25
	All oil collars		5,693,000
	Gas Contracts
	Gas Swaps
	Contract Period		Volumes			Weighted-Average
						Contract Price
			(MMBtu)			(per MMBtu)
	Second quarter 2014		23,758,000			$	3.98
	Third quarter 2014		24,541,000			$	4.02
	Fourth quarter 2014		22,014,000			$	4.02
	2015		57,943,000			$	4.04
	2016		37,472,000			$	4.17
	2017		23,430,000			$	4.21
	2018		10,200,000			$	4.31
	All gas swaps*		199,358,000
	*Gas swaps are comprised of IF El Paso Permian (3%), IF HSC (83%), IF NGPL TXOK (2%), IF NNG Ventura (3%), IF Reliant N/S (8%), and IF CIG N System (1%).
	Gas Collars
	Contract Period		Volumes			Weighted-				Weighted-
						Average Floor				Average Ceiling
						Price				Price
			(MMBtu)			(per MMBtu)				(per MMBtu)
	Second quarter 2014		4,194,000			$	4.38			$	5.29
	2015		13,002,000			$	3.98			$	4.3
	All gas collars*		17,196,000
	*Gas collars are comprised of IF El Paso Permian (3%), IF HSC (64%), IF NGPL TXOK (3%), IF NNG Ventura (6%), IF Reliant N/S (16%), and IF TETCO STX (8%).
	NGL Contracts
	NGL Swaps
	Contract Period		Volumes			Weighted-Average
						Contract Price
			(Bbls)			(per Bbl)
	Second quarter 2014		1,096,000			$	58.04
	Third quarter 2014		960,000			$	58.06
	Fourth quarter 2014		861,000			$	58.06
	All NGL swaps*		2,917,000
	*NGL swaps are comprised of Oil Price Information System (“OPIS”) Mont Belvieu LDH Propane (72%) and OPIS Mont Belvieu NON-LDH Natural Gasoline (28%).
	Derivative Assets and Liabilities Fair Value
	The Company’s commodity derivatives are measured at fair value and are included in the accompanying balance sheets as derivative assets and liabilities. The fair value of the commodity derivative contracts was a net liability of $47.2 million and net asset of $21.5 million at March 31, 2014, and December 31, 2013, respectively.
	The following tables detail the fair value of derivatives recorded in the accompanying balance sheets, by category:
	As of March 31, 2014
	Derivative Assets						Derivative Liabilities
	Balance Sheet		Fair Value				Balance Sheet		Fair Value
	Classification						Classification
	(in thousands)
Commodity contracts	Current assets		$	7,450			Current liabilities		$	60,684
Commodity contracts	Noncurrent assets		13,886				Noncurrent liabilities		7,885
Derivatives not designated as hedging instruments			$	21,336					$	68,569
	As of December 31, 2013
	Derivative Assets						Derivative Liabilities
	Balance Sheet		Fair Value				Balance Sheet		Fair Value
	Classification						Classification
	(in thousands)
Commodity contracts	Current assets		$	21,559			Current liabilities		$	26,380
Commodity contracts	Noncurrent assets		30,951				Noncurrent liabilities		4,640
Derivatives not designated as hedging instruments			$	52,510					$	31,020
Offsetting of Derivative Assets and Liabilities
As of March 31, 2014, and December 31, 2013, all derivative instruments held by the Company were subject to enforceable master netting arrangements held by various financial institutions. In general, the terms of the Company’s agreements provide for offsetting of amounts payable or receivable between it and the counterparty, at the election of both parties, for settlements that occur on the same date and in the same currency. The Company’s agreements also provide that in the event of an early termination, the counterparties have the right to offset amounts owed or owing under that and any other agreement with the same counterparty. The Company’s accounting policy is to not offset these positions in its accompanying balance sheets.
The following table provides a reconciliation between the gross assets and liabilities reflected on the accompanying balance sheets and the potential effects of master netting arrangements on the fair value of the Company’s derivative contracts:
		Derivative Assets								Derivative Liabilities
		As of								As of
Offsetting of Derivative Assets and Liabilities		March 31, 2014				December 31, 2013				March 31, 2014			December 31, 2013
		(in thousands)
Gross amounts presented in the accompanying balance sheets		$	21,336			$	52,510			$	(68,569	)	$	(31,020	)
Amounts not offset in the accompanying balance sheets		(21,336		)		(30,652		)		21,336			30,652
Net amounts		$	—			$	21,858			$	(47,233	)	$	(368	)
The following table summarizes the components of the derivative loss presented in the accompanying statements of operations:
	For the Three Months Ended March 31,
	2014				2013
	(in thousands)
Derivative cash settlement loss (gain):
Oil contracts	$	6,758			$	277
Gas contracts	13,404				(9,824		)
NGL contracts	8,778				(2,245		)
Total derivative cash settlement loss (gain) (1)	28,940				(11,792		)
Derivative loss (gain):
Oil contracts	25,192				3,789
Gas contracts	46,057				40,069
NGL contracts	(2,527		)		(1,494		)
Total derivative loss (2)	$	97,662			$	30,572
____________________________________________
(1)	Total derivative cash settlement loss (gain) is reported in the derivative cash settlement (loss) gain line item on the condensed consolidated statements of cash flows within net cash provided by operating activities.
(2)	Total derivative loss is reported in the derivative loss line item on the condensed consolidated statements of cash flows within cash provided by operating activities.
Credit Related Contingent Features
As of March 31, 2014, and through the filing date of this report, all of the Company’s derivative counterparties were members of the Company’s credit facility lender group. The Company’s obligations under its derivative contracts are secured by liens on at least 75 percent of the Company’s proved oil and gas properties.

Fair_Value_Measurements_Fair_V

Fair Value Measurements Fair Value Measurements	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Disclosures [Text Block]	'
	Note 11 - Fair Value Measurements
	The Company follows fair value measurement authoritative accounting guidance for all assets and liabilities measured at fair value. That authoritative accounting guidance defines fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. Market or observable inputs are the preferred sources of values, followed by assumptions based on hypothetical transactions in the absence of market inputs. The fair value hierarchy for grouping these assets and liabilities is based on the significance level of the following inputs:
	•	Level 1 – quoted prices in active markets for identical assets or liabilities
	•	Level 2 – quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations whose inputs are observable or whose significant value drivers are observable
	•	Level 3 – significant inputs to the valuation model are unobservable
	The following is a listing of the Company’s assets and liabilities that are measured at fair value and their classification within the fair value hierarchy as of March 31, 2014:
		Level 1			Level 2		Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	21,336	$	—
	Liabilities:
	Derivatives (1)	$	—		$	68,569	$	—
	Net Profits Plan (1)	$	—		$	—	$	55,209
	____________________________________________
	(1) This represents a financial asset or liability that is measured at fair value on a recurring basis.
	The following is a listing of the Company’s assets and liabilities that are measured at fair value and their classification within the fair value hierarchy as of December 31, 2013:
		Level 1			Level 2		Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	52,510	$	—
	Proved oil and gas properties (2)	$	—		$	—	$	62,178
	Unproved oil and gas properties (2)	$	—		$	—	$	3,280
	Oil and gas properties held for sale (2)	$	—		$	—	$	650
	Liabilities:
	Derivatives (1)	$	—		$	31,020	$	—
	Net Profits Plan (1)	$	—		$	—	$	56,985
	____________________________________________
	(1) This represents a financial asset or liability that is measured at fair value on a recurring basis.
	(2) This represents a non-financial asset or liability that is measured at fair value on a nonrecurring basis.
	Both financial and non-financial assets and liabilities are categorized within the above fair value hierarchy based on the lowest level of input that is significant to the fair value measurement. The following is a description of the valuation methodologies used by the Company as well as the general classification of such instruments pursuant to the above fair value hierarchy.
	Derivatives
	The Company uses Level 2 inputs to measure the fair value of oil, gas, and NGL commodity derivatives. Fair values are based upon interpolated data. The Company derives internal valuation estimates taking into consideration the counterparties’ credit ratings, the Company’s credit rating, and the time value of money. These valuations are then compared to the respective counterparties’ mark-to-market statements. These factors result in an estimated exit-price that management believes provides a reasonable and consistent methodology for valuing derivative instruments. The derivative instruments utilized by the Company are not considered by management to be complex, structured, or illiquid. The oil, gas, and NGL commodity derivative markets are highly active.
	Generally, market quotes assume that all counterparties have near zero, or low, default rates and have equal credit quality. However, an adjustment may be necessary to reflect the credit quality of a specific counterparty to determine the fair value of the instrument. The Company monitors the credit ratings of its counterparties and may require counterparties to post collateral if their ratings deteriorate. In some instances the Company will attempt to novate the trade to a more stable counterparty.
	Valuation adjustments are necessary to reflect the effect of the Company’s credit quality on the fair value of any liability position with a counterparty. This adjustment takes into account any credit enhancements, such as collateral margin that the Company may have posted with a counterparty, as well as any letters of credit between the parties. The methodology to determine this adjustment is consistent with how the Company evaluates counterparty credit risk, taking into account the Company’s credit rating, current credit facility margins, and any change in such margins since the last measurement date. All of the Company’s derivative counterparties are members of the Company’s credit facility lender group.
	The methods described above may result in a fair value estimate that may not be indicative of net realizable value or may not be reflective of future fair values and cash flows. While the Company believes that the valuation methods utilized are appropriate and consistent with authoritative accounting guidance and with other marketplace participants, the Company recognizes that third parties may use different methodologies or assumptions to determine the fair value of certain financial instruments that could result in a different estimate of fair value at the reporting date.
	Refer to Note 10 - Derivative Financial Instruments for more information regarding the Company’s derivative instruments.
	Net Profits Plan
	The Net Profits Plan is a standalone liability for which there is no available market price, principal market, or market participants. The inputs available for this instrument are unobservable and are therefore classified as Level 3 inputs. The Company employs the income approach, which converts expected future cash flow amounts to a single present value amount. This technique uses the estimate of future cash payments, expectations of possible variations in the amount and/or timing of cash flows, the risk premium, and nonperformance risk to calculate the fair value. There is a direct correlation between realized oil, gas, and NGL commodity prices driving net cash flows and the Net Profits Plan liability. Generally, higher commodity prices result in a larger Net Profits Plan liability and lower commodity prices result in a smaller Net Profits Plan liability.
	The Company records the estimated fair value of the long-term liability for estimated future payments under the Net Profits Plan based on the discounted value of estimated future payments associated with each individual pool. The calculation of this liability is a significant management estimate. A discount rate of 12 percent is used to calculate this liability and is intended to represent the Company’s best estimate of the present value of expected future payments under the Net Profits Plan.
	The Company’s estimate of its liability is highly dependent on commodity prices, cost assumptions, discount rates, and overall market conditions. The Company regularly assesses the current market environment.  The Net Profits Plan liability is determined using price assumptions of five one-year strip prices with the fifth year’s pricing then carried out indefinitely. The average price is adjusted for realized price differentials and to include the effects of the forecasted production covered by derivatives contracts in the relevant periods.  The non-cash expense associated with this significant management estimate is highly volatile from period to period due to fluctuations that occur in the oil, gas, and NGL commodity markets.
	If the commodity prices used in the calculation changed by five percent, the liability recorded at March 31, 2014, would differ by approximately $5 million. A one percent increase or decrease in the discount rate would result in a change of approximately $2 million. Actual cash payments to be made to participants in future periods are dependent on realized actual production, realized commodity prices, and costs associated with the properties in each individual pool of the Net Profits Plan. Consequently, actual cash payments are inherently different from the amounts estimated.
	No published market quotes exist on which to base the Company’s estimate of fair value of its Net Profits Plan liability. As such, the recorded fair value is based entirely on management estimates that are described within this footnote. While some inputs to the Company’s calculation of fair value on the Net Profits Plan’s future payments are from published sources, others, such as the discount rate and the expected future cash flows, are derived from the Company’s own calculations and estimates.
	The following table reflects the activity for the Company’s Net Profits Plan liability measured at fair value using Level 3 inputs:
		For the Three Months Ended March 31, 2014
		(in thousands)
	Beginning balance	$	56,985
	Net increase in liability (1)	1,707
	Net settlements (1) (2)	(3,483		)
	Transfers in (out) of Level 3	—
	Ending balance	$	55,209
	____________________________________________
	(1)	Net changes in the Company’s Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item of the accompanying statements of operations.
	(2)	Settlements represent cash payments made or accrued under the Net Profits Plan. The Company accrued or made cash payments under the Net Profits Plan of $217,000 relating to divestiture proceeds for the three months ended March 31, 2014.
	Long-term Debt
	The following table reflects the fair value of the Senior Notes measured using Level 1 inputs based on quoted secondary market trading prices. The Senior Notes were not presented at fair value on the accompanying balance sheets as of March 31, 2014, or December 31, 2013, as they are recorded at historical value.
		As of March 31, 2014			As of December 31, 2013
		(in thousands)
	2019 Notes	$	375,375		$	374,290
	2021 Notes	$	376,250		$	373,625
	2023 Notes	$	428,760		$	422,000
	2024 Notes	$	488,440		$	475,315
	As of March 31, 2014, the Company had no floating-rate debt outstanding.
	Proved and Unproved Oil and Gas Properties
Proved oil and gas property costs are evaluated for impairment and reduced to fair value when there is an indication that the carrying costs may not be recoverable. The Company uses Level 3 inputs and the income valuation technique, which converts future amounts to a single present value amount, to measure the fair value of proved properties through an application of discount rates and price forecasts selected by the Company’s management. The calculation of the discount rate is based on the best information available and was estimated to be 12 percent as of March 31, 2014, and December 31, 2013. The Company believes that the discount rate is representative of current market conditions and takes into account estimates of future cash payments, expectations of possible variations in the amount and/or timing of cash flows, the risk premium, and nonperformance risk. The prices for oil and gas are forecasted based on New York Mercantile Exchange (“NYMEX”) strip pricing, adjusted for basis differentials, for the first five years, after which a flat terminal price is used for each commodity stream. The prices for NGLs are forecasted using OPIS Mont Belvieu pricing, for as long as the market is actively trading, after which a flat terminal price is used. Future operating costs are also adjusted as deemed appropriate for these estimates. Proved properties classified as held for sale are valued using a market approach, based on an estimated selling price, as evidenced by the most current bid prices received from third parties. If an estimated selling price is not available, the Company utilizes the income valuation technique discussed above.
Unproved oil and gas property costs are evaluated for impairment and reduced to fair value when there is an indication that the carrying costs may not be recoverable.  To measure the fair value of unproved properties, the Company uses a market approach, which takes into account the following significant assumptions: future development plans, risk weighted potential resource recovery, and estimated reserve values. Unproved properties classified as held for sale are valued using a market approach, based on an estimated selling price, as evidenced by the most current bid prices received from third parties. If an estimated selling price is not available, the Company estimates acreage value based on the price received for similar acreage in recent transactions by the Company or other market participants in the principal market.
Acquisitions of proved and unproved properties are measured at fair value as of the acquisition date using an income valuation technique similar to the Company’s approach in measuring the fair value of proved and unproved properties, as discussed above. Due to the unobservable characteristics of the inputs, the fair value of acquired properties are considered Level 3 within the fair value hierarchy.
Asset Retirement Obligations
The Company utilizes the income valuation technique to determine the fair value of the asset retirement obligation liability at the point of inception by applying a credit-adjusted risk-free rate, which takes into account the Company’s credit risk, the time value of money, and the current economic state, to the undiscounted expected abandonment cash flows. Given the unobservable nature of the inputs, the initial measurement of the asset retirement obligation liability is deemed to use Level 3 inputs. There were no asset retirement obligations recorded at fair value in the accompanying balance sheets at March 31, 2014, or December 31, 2013.

Basis_of_Presentation_Signific1

Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards (Policies)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Non-qualified Deferred Compensation Plan [Policy Text Block]	'
	Non-qualified Deferred Compensation Plan
	In January 2014, the Company established a non-qualified deferred compensation (“NQDC”) plan intended to provide plan participants with the ability to plan for income tax events and the opportunity to receive a benefit for matching contributions in excess of Internal Revenue Code (“IRC”) limits applicable to the Company’s 401(k) plan. The NQDC plan is designed to allow participants to defer a portion of base salary and cash bonuses paid pursuant to the Company’s cash bonus plan. Each year, participating employees may elect to defer (i) between 0% and 50% of their base salary, and (ii) between 0% and 100% of the cash bonus paid pursuant to the cash bonus plan. The NQDC plan requires the Company to make contributions for each eligible employee equal to 100% of the deferred amount for such employee, limited to 6% of such employee’s base salary and cash bonus. Each eligible employee’s interest in the contributions the Company makes will vest 40% after the second year of such employee’s service to the Company, and 20% per year thereafter. A participant’s account will be distributed based upon the participant’s payment election made at the time of deferral. A participant may elect to have distributions made in lump sum or in annual installments ranging for a period from 1 to 10 years.
Description and terms of the Performance Share Awards	'
	Performance Stock Units Under the Equity Incentive Compensation Plan
	The Company grants performance share units (“PSUs”) as part of its equity compensation program. The number of shares of the Company’s common stock issued to settle PSUs ranges from 0% to 200% of the number of PSUs awarded and is determined based on the Company’s performance over a three-year measurement period. The performance criteria for the PSUs are based on a combination of the Company’s annualized total shareholder return (“TSR”) for the measurement period and the relative measure of the Company’s TSR compared with the annualized TSRs of a group of peer companies for the measurement period. Expense associated with PSUs is recognized as G&A expense and exploration expense over the vesting period of the award.
Fair value of financial instruments measured on a recurring Basis	'
	The Company uses Level 2 inputs to measure the fair value of oil, gas, and NGL commodity derivatives. Fair values are based upon interpolated data. The Company derives internal valuation estimates taking into consideration the counterparties’ credit ratings, the Company’s credit rating, and the time value of money. These valuations are then compared to the respective counterparties’ mark-to-market statements. These factors result in an estimated exit-price that management believes provides a reasonable and consistent methodology for valuing derivative instruments. The derivative instruments utilized by the Company are not considered by management to be complex, structured, or illiquid. The oil, gas, and NGL commodity derivative markets are highly active.
	Generally, market quotes assume that all counterparties have near zero, or low, default rates and have equal credit quality. However, an adjustment may be necessary to reflect the credit quality of a specific counterparty to determine the fair value of the instrument. The Company monitors the credit ratings of its counterparties and may require counterparties to post collateral if their ratings deteriorate. In some instances the Company will attempt to novate the trade to a more stable counterparty.
	Valuation adjustments are necessary to reflect the effect of the Company’s credit quality on the fair value of any liability position with a counterparty. This adjustment takes into account any credit enhancements, such as collateral margin that the Company may have posted with a counterparty, as well as any letters of credit between the parties. The methodology to determine this adjustment is consistent with how the Company evaluates counterparty credit risk, taking into account the Company’s credit rating, current credit facility margins, and any change in such margins since the last measurement date. All of the Company’s derivative counterparties are members of the Company’s credit facility lender group.
	The methods described above may result in a fair value estimate that may not be indicative of net realizable value or may not be reflective of future fair values and cash flows. While the Company believes that the valuation methods utilized are appropriate and consistent with authoritative accounting guidance and with other marketplace participants, the Company recognizes that third parties may use different methodologies or assumptions to determine the fair value of certain financial instruments that could result in a different estimate of fair value at the reporting date.
	Refer to Note 10 - Derivative Financial Instruments for more information regarding the Company’s derivative instruments.

Earnings_per_Share_Tables

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Schedule of calculation of basic and diluted earnings per share	'
	The following table sets forth the calculations of basic and diluted earnings per share:
		For the Three Months Ended March 31,
		2014		2013
		(in thousands, except per share amounts)
	Net income	$	65,607	$	16,727
	Basic weighted-average common shares outstanding	67,056		66,211
	Add: dilutive effect of stock options, unvested RSUs, and contingent PSUs	1,070		1,310
	Diluted weighted-average common shares outstanding	68,126		67,521
	Basic net income per common share	$	0.98	$	0.25
	Diluted net income per common share	$	0.96	$	0.25

Income_Taxes_Tables

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2014
Income Tax Disclosure [Abstract]	'
Schedule of provision for income taxes	'
	The provision for income taxes consists of the following:
		For the Three Months Ended March 31,
		2014			2013
		(in thousands)
	Current portion of income tax expense:
	Federal	$	—		$	—
	State	489			102
	Deferred portion of income tax expense	38,374			10,280
	Total income tax expense	$	38,863		$	10,382
		37.2		%	38.3		%

LongTerm_Debt_Tables

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Schedule of Long-Term Debt Principal Outstanding [Table Text Block]	'
	The Senior Notes line on the accompanying balance sheets represents the outstanding principal amount of the 6.625% Senior Notes due 2019 (the “2019 Notes”), the 6.50% Senior Notes due 2021 (the “2021 Notes”), the 6.50% Senior Notes due 2023 (the “2023 Notes”), and the 5.0% Senior Notes due 2024 (the “2024 Notes” and collectively with the 2019 Notes, 2021 Notes, and 2023 Notes, the “Senior Notes”), as shown in the table below:
		As of March 31, 2014		As of December 31, 2013
		(in thousands)
	2019 Notes	$	350,000	$	350,000
	2021 Notes	350,000		350,000
	2023 Notes	400,000		400,000
	2024 Notes	500,000		500,000
	Total Senior Notes	$	1,600,000	$	1,600,000
Schedule of Long-term Debt Instruments [Table Text Block]	'
	The following table presents the outstanding balance, total amount of letters of credit, and available borrowing capacity under the Company’s credit facility as of April 23, 2014, March 31, 2014, and December 31, 2013:
		As of April 23, 2014		As of March 31, 2014		As of December 31, 2013
		(in thousands)
	Credit facility balance	$	—	$	—	$	—
	Letters of credit (1)	$	808	$	808	$	808
	Available borrowing capacity	$	1,299,192	$	1,299,192	$	1,299,192
	____________________________________________
	(1) Letters of credit reduce the available borrowing capacity under the credit facility on a dollar-for-dollar basis.

Compensation_Plans_Tables

Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Schedule of Net Profits Plan Cash Payment Allocation	'
	Cash payments made or accrued under the Company’s Net Profits Interest Bonus Plan (“Net Profits Plan”) that have been recorded as either G&A expense or exploration expense are presented in the table below:
		For the Three Months Ended March 31,
		2014		2013
		(in thousands)
	General and administrative expense	$	2,978	$	3,786
	Exploration expense	288		374
	Total	$	3,266	$	4,160

Pension_Benefits_Tables

Pension Benefits (Tables)	3 Months Ended
	Mar. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]	'
Components of the net periodic benefit cost for both the Qualified and the Nonqualified Pension Plan	'
	The following table presents the components of the net periodic benefit cost for the Pension Plans:
		For the Three Months Ended March 31,
		2014			2013
		(in thousands)
	Service cost	$	1,573		$	1,232
	Interest cost	407			345
	Expected return on plan assets that reduces periodic pension costs	(385		)	(286		)
	Amortization of prior service costs	4			4
	Amortization of net actuarial loss	306			197
	Net periodic benefit cost	$	1,905		$	1,492

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]	'
	The following tables summarize the approximate volumes and average contract prices of contracts the Company had in place as of March 31, 2014, and through the filing date of this report:
	Oil Contracts
	Oil Swaps
	Contract Period		NYMEX WTI Volumes			Weighted-Average
						Contract Price
			(Bbls)			(per Bbl)
	Second quarter 2014		2,373,000			$	94.95
	Third quarter 2014		1,533,000			$	96.04
	Fourth quarter 2014		1,353,000			$	94.88
	2015		3,308,000			$	89.34
	2016		2,704,000			$	85.19
	All oil swaps		11,271,000
	Oil Collars
	Contract Period		NYMEX WTI			Weighted-				Weighted-
			Volumes			Average Floor				Average Ceiling
						Price				Price
			(Bbls)			(per Bbl)				(per Bbl)
	Second quarter 2014		431,000			$	85			$	102.5
	Third quarter 2014		973,000			$	85			$	102.58
	Fourth quarter 2014		923,000			$	85			$	102.63
	2015		3,366,000			$	85			$	94.25
	All oil collars		5,693,000
	Gas Contracts
	Gas Swaps
	Contract Period		Volumes			Weighted-Average
						Contract Price
			(MMBtu)			(per MMBtu)
	Second quarter 2014		23,758,000			$	3.98
	Third quarter 2014		24,541,000			$	4.02
	Fourth quarter 2014		22,014,000			$	4.02
	2015		57,943,000			$	4.04
	2016		37,472,000			$	4.17
	2017		23,430,000			$	4.21
	2018		10,200,000			$	4.31
	All gas swaps*		199,358,000
	*Gas swaps are comprised of IF El Paso Permian (3%), IF HSC (83%), IF NGPL TXOK (2%), IF NNG Ventura (3%), IF Reliant N/S (8%), and IF CIG N System (1%).
	Gas Collars
	Contract Period		Volumes			Weighted-				Weighted-
						Average Floor				Average Ceiling
						Price				Price
			(MMBtu)			(per MMBtu)				(per MMBtu)
	Second quarter 2014		4,194,000			$	4.38			$	5.29
	2015		13,002,000			$	3.98			$	4.3
	All gas collars*		17,196,000
	*Gas collars are comprised of IF El Paso Permian (3%), IF HSC (64%), IF NGPL TXOK (3%), IF NNG Ventura (6%), IF Reliant N/S (16%), and IF TETCO STX (8%).
	NGL Contracts
	NGL Swaps
	Contract Period		Volumes			Weighted-Average
						Contract Price
			(Bbls)			(per Bbl)
	Second quarter 2014		1,096,000			$	58.04
	Third quarter 2014		960,000			$	58.06
	Fourth quarter 2014		861,000			$	58.06
	All NGL swaps*		2,917,000
	*NGL swaps are comprised of Oil Price Information System (“OPIS”) Mont Belvieu LDH Propane (72%) and OPIS Mont Belvieu NON-LDH Natural Gasoline (28%).
Schedule of fair value of derivatives in accompanying balance sheets	'
	The following tables detail the fair value of derivatives recorded in the accompanying balance sheets, by category:
		As of March 31, 2014
		Derivative Assets						Derivative Liabilities
		Balance Sheet		Fair Value				Balance Sheet		Fair Value
		Classification						Classification
		(in thousands)
	Commodity contracts	Current assets		$	7,450			Current liabilities		$	60,684
	Commodity contracts	Noncurrent assets		13,886				Noncurrent liabilities		7,885
	Derivatives not designated as hedging instruments			$	21,336					$	68,569
		As of December 31, 2013
		Derivative Assets						Derivative Liabilities
		Balance Sheet		Fair Value				Balance Sheet		Fair Value
		Classification						Classification
		(in thousands)
	Commodity contracts	Current assets		$	21,559			Current liabilities		$	26,380
	Commodity contracts	Noncurrent assets		30,951				Noncurrent liabilities		4,640
	Derivatives not designated as hedging instruments			$	52,510					$	31,020
Schedule of the potential effects of master netting arrangements [Table Text Block]	'
	The following table provides a reconciliation between the gross assets and liabilities reflected on the accompanying balance sheets and the potential effects of master netting arrangements on the fair value of the Company’s derivative contracts:
			Derivative Assets								Derivative Liabilities
			As of								As of
	Offsetting of Derivative Assets and Liabilities		March 31, 2014				December 31, 2013				March 31, 2014			December 31, 2013
			(in thousands)
	Gross amounts presented in the accompanying balance sheets		$	21,336			$	52,510			$	(68,569	)	$	(31,020	)
	Amounts not offset in the accompanying balance sheets		(21,336		)		(30,652		)		21,336			30,652
	Net amounts		$	—			$	21,858			$	(47,233	)	$	(368	)
Schedule of derivative (gain) loss	'
	The following table summarizes the components of the derivative loss presented in the accompanying statements of operations:
		For the Three Months Ended March 31,
		2014				2013
		(in thousands)
	Derivative cash settlement loss (gain):
	Oil contracts	$	6,758			$	277
	Gas contracts	13,404				(9,824		)
	NGL contracts	8,778				(2,245		)
	Total derivative cash settlement loss (gain) (1)	28,940				(11,792		)
	Derivative loss (gain):
	Oil contracts	25,192				3,789
	Gas contracts	46,057				40,069
	NGL contracts	(2,527		)		(1,494		)
	Total derivative loss (2)	$	97,662			$	30,572
	____________________________________________
	(1)	Total derivative cash settlement loss (gain) is reported in the derivative cash settlement (loss) gain line item on the condensed consolidated statements of cash flows within net cash provided by operating activities.
	(2)	Total derivative loss is reported in the derivative loss line item on the condensed consolidated statements of cash flows within cash provided by operating activities.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block]	'
	The following is a listing of the Company’s assets and liabilities that are measured at fair value and their classification within the fair value hierarchy as of March 31, 2014:
		Level 1			Level 2		Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	21,336	$	—
	Liabilities:
	Derivatives (1)	$	—		$	68,569	$	—
	Net Profits Plan (1)	$	—		$	—	$	55,209
	____________________________________________
	(1) This represents a financial asset or liability that is measured at fair value on a recurring basis.
	The following is a listing of the Company’s assets and liabilities that are measured at fair value and their classification within the fair value hierarchy as of December 31, 2013:
		Level 1			Level 2		Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	52,510	$	—
	Proved oil and gas properties (2)	$	—		$	—	$	62,178
	Unproved oil and gas properties (2)	$	—		$	—	$	3,280
	Oil and gas properties held for sale (2)	$	—		$	—	$	650
	Liabilities:
	Derivatives (1)	$	—		$	31,020	$	—
	Net Profits Plan (1)	$	—		$	—	$	56,985
	____________________________________________
	(1) This represents a financial asset or liability that is measured at fair value on a recurring basis.
	(2) This represents a non-financial asset or liability that is measured at fair value on a nonrecurring basis.
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	'
	The following table reflects the activity for the Company’s Net Profits Plan liability measured at fair value using Level 3 inputs:
		For the Three Months Ended March 31, 2014
		(in thousands)
	Beginning balance	$	56,985
	Net increase in liability (1)	1,707
	Net settlements (1) (2)	(3,483		)
	Transfers in (out) of Level 3	—
	Ending balance	$	55,209
	____________________________________________
	(1)	Net changes in the Company’s Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item of the accompanying statements of operations.
	(2)	Settlements represent cash payments made or accrued under the Net Profits Plan. The Company accrued or made cash payments under the Net Profits Plan of $217,000 relating to divestiture proceeds for the three months ended March 31, 2014.
Fair Value, by Balance Sheet Grouping [Table Text Block]	'
	The following table reflects the fair value of the Senior Notes measured using Level 1 inputs based on quoted secondary market trading prices. The Senior Notes were not presented at fair value on the accompanying balance sheets as of March 31, 2014, or December 31, 2013, as they are recorded at historical value.
		As of March 31, 2014			As of December 31, 2013
		(in thousands)
	2019 Notes	$	375,375		$	374,290
	2021 Notes	$	376,250		$	373,625
	2023 Notes	$	428,760		$	422,000
	2024 Notes	$	488,440		$	475,315

Assets_Held_for_Sale_Details

Assets Held for Sale (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Apr. 23, 2014	Dec. 31, 2013
Assets held for sale [Abstract]	'	'	'
Cash Consideration to Acquire Unproved Property	'	$100,000,000	'
Leasehold Acres Consideration to Acquire Unproved Property	'	7,000	'
Assets Held-for-sale Reasonably Certain Period for Sale	1	'	'
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	42,276,000	'	19,072,000
Asset retirement obligation associated with oil and gas properties held for sale	$4,526,000	'	$3,033,000

Earnings_per_Share_Details

Earnings per Share (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Calculation of basic and diluted earnings per share	'	'
Net income	$65,607	$16,727
Basic weighted-average common shares outstanding	67,056	66,211
Add: dilutive effect of stock options, unvested RSU's, and contingent PSU's	1,070	1,310
Diluted weighted-average common shares outstanding	68,126	67,521
Basic net income per common share	$0.98	$0.25
Diluted net income per common share	$0.96	$0.25
Performance Shares [Member]	'	'
Earnings per share	'	'
Performance period to receive awards (in years)	3	'
Common stock awards vesting multiplier, low end of range	0	'
Common stock awards vesting multiplier, high end of range	2	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Components of the provision for income taxes	'	'
Federal	$0	$0
State	489	102
Deferred portion of income tax expense	38,374	10,280
Income tax expense	$38,863	$10,382
Effective tax rate	37.20%	38.30%

Income_Taxes_Narrative_Details

Income Taxes Narrative (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Income Tax Narrative [Abstract]	'
IRS Proposed R&D Tax Adjustment	$4.60

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	20-May-13	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
			Line of Credit [Member]	5.0% Senior Notes Due 2024 [Member]	5.0% Senior Notes Due 2024 [Member]	Revolving Credit Facility [Member]	Senior Notes [Member]	Senior Notes [Member]
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'
Line of Credit Facility, Maximum Borrowing Capacity	'	'	$2,500,000,000	'	'	'	'	'
Line of Credit Facility, Current Borrowing Capacity	'	'	1,300,000,000	'	'	'	'	'
Borrowing Base, Line of Credit	'	'	2,200,000,000	'	'	'	'	'
Percentage of Proved Oil and Gas Properties Secured for Credit Facility Borrowing	'	'	'	'	'	75.00%	'	'
Line of Credit, Covenant Compliance, Maximum Annual Dividend Payment	'	'	50,000,000	'	'	'	'	'
Debt Instrument, Covenant Compliance, Dividends Excluded From Computation	'	'	'	6,500,000	'	'	'	'
Interest rate on notes (as a percent)	'	'	'	'	5.00%	'	'	'
Debt Instrument, Face Amount	'	'	'	'	500,000,000	'	'	'
6.625% Senior Notes, Due 2019	'	'	'	'	'	'	350,000,000	350,000,000
6.50% Senior Notes, Due 2021	'	'	'	'	'	'	350,000,000	350,000,000
6.50% Senior Notes, Due 2023	'	'	'	'	'	'	400,000,000	400,000,000
5% Senior Notes, Due 2024	'	'	'	'	'	'	500,000,000	500,000,000
Senior Notes	$1,600,000,000	$1,600,000,000	'	'	'	'	$1,600,000,000	$1,600,000,000

LongTerm_Debt_Credit_Facility_

Long-Term Debt Credit Facility Available Borrowing Capacity (Details) (USD $)	Apr. 23, 2014		Mar. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Credit Facility Available Borrowing Capacity [Abstract]	'		'		'
Revolving credit facility	$0		$0		$0
Letters of Credit Outstanding, Amount	808	[1]	808	[1]	808	[1]
Line of Credit Facility, Remaining Borrowing Capacity	$1,299,192		$1,299,192		$1,299,192
[1]	(1) Letters of credit reduce the available borrowing capacity under the credit facility on a dollar-for-dollar basis.

Commitments_and_Contingencies_

Commitments and Contingencies Narrative (Details) (Drilling Rig Leasing Contracts [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Drilling Rig Leasing Contracts [Member]	'
Long-term Purchase Commitment [Line Items]	'
Long-term Purchase Commitment, Amount	$52.70

Compensation_Plans_Details

Compensation Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
RSUs, PSUs, and Director's Shares [Abstract]	'	'
Stock-based compensation expense	$6,344,000	$8,113,000
Cash Bonus Plan [Member]	'	'
Compensation plans	'	'
Accrued Cash Bonus Plan Expense	6,600,000	5,600,000
Restricted Stock Units (RSUs) [Member]	'	'
RSUs, PSUs, and Director's Shares [Abstract]	'	'
Number of Common Shares to be Received Upon Settlement	1	'
Stock-based compensation expense	2,800,000	3,000,000
Unrecognized stock based compensation expense	15,900,000	'
Performance Shares [Member]	'	'
RSUs, PSUs, and Director's Shares [Abstract]	'	'
Stock-based compensation expense	3,200,000	4,700,000
Unrecognized stock based compensation expense	14,900,000	'
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Low End of Range	0	'
Common stock awards vesting multiplier, high end of range	2	'
Share-based Compensation, Awards Other Than Options, Performance Measurement Period	3	'
Employee Stock Option [Member]	'	'
Stock option activity	'	'
Stock options outstanding at the end of the period (in shares)	39,088	'
Weighted-Average Exercise Price	'	'
Stock options outstanding at the end of the period (in dollars per share)	$20.87	'
Aggregate Intrinsic Value	'	'
Vested at the end of the period	$1,971,000	'

Compensation_Plans_Non_Stockba

Compensation Plans Non Stock-based Compensation (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Document Period End Date	31-Mar-14	'
Cash Bonus Plan [Member]	'	'
Cash Paid in Current Period for Bonus Compensation	$41,700,000	$16,000,000
Accrued Cash Bonus Plan Expense	6,600,000	5,600,000
Net Profits Plan [Member]	'	'
General and administrative expense	2,978,000	3,786,000
Exploration expense	288,000	374,000
Total	$3,266,000	$4,160,000

Compensation_Plans_Nonqualifie

Compensation Plans Non-qualified Deferred Compensation Plan (Details) (Non-qualified Deferred Compensation Plan [Member])	3 Months Ended
	Mar. 31, 2014
	Years
Non-qualified Deferred Compensation Plan [Member]	'
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]	'
Base Salary Minimum Deferral Percentage	0.00%
Base Salary Maximum Deferral Percentage	50.00%
Cash Bonus Minimum Deferral Percentage	0.00%
Cash Bonus Maximum Deferral Percentage	100.00%
Company Percentage Contribution of Employee Deferred Amount	100.00%
Company Percentage Contribution Limit of Employee Deferred Amount	6.00%
Employee Vesting Percentage in Company Contribution After Two Years	40.00%
Employee Vesting Percentage in Company Contribution Year Three and Each Year Thereafter	20.00%
Distribution Option Minimum Years	1
Distribution Option Maximum Years	10

Pension_Benefits_Details

Pension Benefits (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Components of Net Periodic Benefit Costs for Both Pension Plans	'	'
Service cost	$1,573,000	$1,232,000
Interest cost	407,000	345,000
Expected return on plan assets that reduces periodic pension costs	-385,000	-286,000
Amortization of prior service costs	4,000	4,000
Amortization of net actuarial loss	306,000	197,000
Net periodic benefit cost	1,905,000	1,492,000
Percentage in excess of the greater of the benefit obligation or the market-related value of assets, gain and losses amortized (as a percent)	10.00%	'
Defined Benefit Plan, Contributions by Employer	$5,300,000	'

Derivative_Financial_Instrumen2

Derivative Financial Instruments (Details)	3 Months Ended
	Mar. 31, 2014
Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	17,000,000
Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	216,600,000
Natural Gas Liquids	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	2,900,000
IF El Paso Permian [Member]	'
Derivative Financial Instruments	'
Index percent of natural gas fixed swaps	3.00%
Index percent of natural gas collars	3.00%
IF HSC [Member]	'
Derivative Financial Instruments	'
Index percent of natural gas fixed swaps	83.00%
Index percent of natural gas collars	64.00%
IF NGPL TXOK [Member]	'
Derivative Financial Instruments	'
Index percent of natural gas fixed swaps	2.00%
Index percent of natural gas collars	3.00%
IF NNG Ventura [Member]	'
Derivative Financial Instruments	'
Index percent of natural gas fixed swaps	3.00%
Index percent of natural gas collars	6.00%
IF Reliant N/S [Member]	'
Derivative Financial Instruments	'
Index percent of natural gas fixed swaps	8.00%
Index percent of natural gas collars	16.00%
IF NGPL MidCont [Member]	'
Derivative Financial Instruments	'
Index percent of natural gas fixed swaps	1.00%
IF TETCO STX [Member]	'
Derivative Financial Instruments	'
Index percent of natural gas collars	8.00%
OPIS Mont. Belvieu LDH Propane [Member]	'
Derivative Financial Instruments	'
Index percent of NGL fixed swaps	72.00%
OPIS Mont. Belvieu Non-LDH Natural Gasoline [Member]	'
Derivative Financial Instruments	'
Index percent of NGL fixed swaps	28.00%
Swap | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	11,271,000
Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	199,358,000
Swap | Natural Gas Liquids	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	2,917,000
Collar | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	5,693,000
Collar | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	17,196,000
Second Quarter Current Year [Member] | Swap | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	2,373,000
Weighted-Average Contract Price	94.95
Second Quarter Current Year [Member] | Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	23,758,000
Weighted-Average Contract Price	3.98
Second Quarter Current Year [Member] | Swap | Natural Gas Liquids	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	1,096,000
Weighted-Average Contract Price	58.04
Second Quarter Current Year [Member] | Collar | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	431,000
Weighted-Average Floor Price	85
Weighted-Average Ceiling Price	102.5
Second Quarter Current Year [Member] | Collar | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	4,194,000
Weighted-Average Floor Price	4.38
Weighted-Average Ceiling Price	5.29
Third Quarter Current Year [Member] | Swap | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	1,533,000
Weighted-Average Contract Price	96.04
Third Quarter Current Year [Member] | Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	24,541,000
Weighted-Average Contract Price	4.02
Third Quarter Current Year [Member] | Swap | Natural Gas Liquids	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	960,000
Weighted-Average Contract Price	58.06
Third Quarter Current Year [Member] | Collar | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	973,000
Weighted-Average Floor Price	85
Weighted-Average Ceiling Price	102.58
Fourth Quarter Current Year [Member] | Swap | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	1,353,000
Weighted-Average Contract Price	94.88
Fourth Quarter Current Year [Member] | Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	22,014,000
Weighted-Average Contract Price	4.02
Fourth Quarter Current Year [Member] | Swap | Natural Gas Liquids	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	861,000
Weighted-Average Contract Price	58.06
Fourth Quarter Current Year [Member] | Collar | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	923,000
Weighted-Average Floor Price	85
Weighted-Average Ceiling Price	102.63
2015 [Member] | Swap | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	3,308,000
Weighted-Average Contract Price	89.34
2015 [Member] | Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	57,943,000
Weighted-Average Contract Price	4.04
2015 [Member] | Collar | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	3,366,000
Weighted-Average Floor Price	85
Weighted-Average Ceiling Price	94.25
2015 [Member] | Collar | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	13,002,000
Weighted-Average Floor Price	3.98
Weighted-Average Ceiling Price	4.3
2016 [Member] | Swap | Crude oil	'
Derivative Financial Instruments	'
Portion of future oil and NGL production hedged	2,704,000
Weighted-Average Contract Price	85.19
2016 [Member] | Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	37,472,000
Weighted-Average Contract Price	4.17
2017 [Member] | Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	23,430,000
Weighted-Average Contract Price	4.21
2018 [Member] | Swap | Natural Gas	'
Derivative Financial Instruments	'
Portion of Gas Production Being Hedged	10,200,000
Weighted-Average Contract Price	4.31
Revolving Credit Facility [Member]	'
Derivative Financial Instruments	'
Percentage of Proved Oil and Gas Properties Secured for Credit Facility Borrowing	75.00%

Derivative_Financial_Instrumen3

Derivative Financial Instruments Fair Value (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Fair value of derivative assets and liabilities	'	'
Price Risk Derivatives, at Fair Value, Net	($47,200,000)	$21,500,000
Derivative asset current	7,450,000	21,559,000
Derivative asset noncurrent	13,886,000	30,951,000
Derivative liability current	60,684,000	26,380,000
Derivatives liability noncurrent	7,885,000	4,640,000
Derivatives not designated as hedging instruments	'	'
Fair value of derivative assets and liabilities	'	'
Derivative asset current	7,450,000	21,559,000
Derivative asset noncurrent	13,886,000	30,951,000
Derivative liability current	60,684,000	26,380,000
Derivatives liability noncurrent	7,885,000	4,640,000
Level 2 | Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member]	'	'
Fair value of derivative assets and liabilities	'	'
Derivative assets not designated as hedging instruments	21,336,000	52,510,000
Derivative liabilities not designated as hedging instruments	$68,569,000	$31,020,000

Derivative_Financial_Instrumen4

Derivative Financial Instruments Gains and Losses (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts	'		'
Derivative cash settlement (loss) gain	($28,940)	[1]	$11,792	[1]
Gain (Loss) on Derivative Instruments, Net, Pretax	-97,662	[2]	-30,572	[2]
Crude oil	'		'
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts	'		'
Derivative cash settlement (loss) gain	-6,758		-277
Derivative (gain) loss	25,192		3,789
Natural Gas	'		'
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts	'		'
Derivative cash settlement (loss) gain	-13,404		9,824
Derivative (gain) loss	46,057		40,069
Natural Gas Liquids	'		'
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts	'		'
Derivative cash settlement (loss) gain	-8,778		2,245
Derivative (gain) loss	($2,527)		($1,494)
[1]	(1)B Total derivative cash settlement loss (gain) is reported in the derivative cash settlement (loss) gain line item on the condensed consolidated statements of cash flows within net cash provided by operating activities.
[2]	(2)B Total derivative loss is reported in the derivative loss line item on the condensed consolidated statements of cash flows within cash provided by operating activities.

Derivative_Financial_Instrumen5

Derivative Financial Instruments Offsetting of Derivative Assets and Liabilities (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Offsetting of Derivative Assets and Liabilities [Abstract]	'	'
Derivative Asset, Fair Value, Amount Offset Against Collateral	$21,336	$52,510
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	-21,336	-30,652
Derivative Asset, Fair Value, Amount Offset Against Collateral, Net	0	21,858
Derivative Liability, Fair Value, Amount Offset Against Collateral	-68,569	-31,020
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	21,336	30,652
Derivative Liability, Fair Value, Amount Offset Against Collateral, Net	($47,233)	($368)

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Apr. 23, 2014	Mar. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Assets:	'	'		'
Proved oil and gas properties	'	$5,875,541		$5,637,462
Unproved oil and gas properties	'	287,607		271,100
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	'	42,276		19,072
Liabilities:	'	'		'
Line of Credit Facility, Amount Outstanding	0	0		0
Fair Value, Measurements, Nonrecurring [Member] | Level 1	'	'		'
Assets:	'	'		'
Proved oil and gas properties	'	'		0	[1]
Unproved oil and gas properties	'	'		0	[1]
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	'	'		0	[1]
Fair Value, Measurements, Nonrecurring [Member] | Level 2	'	'		'
Assets:	'	'		'
Proved oil and gas properties	'	'		0	[1]
Unproved oil and gas properties	'	'		0	[1]
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	'	'		0	[1]
Fair Value, Measurements, Nonrecurring [Member] | Level 3	'	'		'
Assets:	'	'		'
Proved oil and gas properties	'	'		62,178	[1]
Unproved oil and gas properties	'	'		3,280	[1]
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $31,776 in 2014 and $7,390 in 2013	'	'		650	[1]
Fair Value, Measurements, Recurring [Member] | Level 1	'	'		'
Liabilities:	'	'		'
Net Profits Plan Liability	'	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Level 2	'	'		'
Liabilities:	'	'		'
Net Profits Plan Liability	'	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Level 3	'	'		'
Liabilities:	'	'		'
Net Profits Plan Liability	'	55,209	[2]	56,985	[2]
Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member] | Level 1	'	'		'
Assets:	'	'		'
Derivatives	'	0	[2]	0	[2]
Liabilities:	'	'		'
Derivatives	'	0	[2]	0	[2]
Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member] | Level 2	'	'		'
Assets:	'	'		'
Derivatives	'	21,336	[2]	52,510	[2]
Liabilities:	'	'		'
Derivatives	'	68,569	[2]	31,020	[2]
Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member] | Level 3	'	'		'
Assets:	'	'		'
Derivatives	'	0	[2]	0	[2]
Liabilities:	'	'		'
Derivatives	'	$0	[2]	$0	[2]
[1]	This represents a non-financial asset or liability that is measured at fair value on a nonrecurring basis.
[2]	This represents a financial asset or liability that is measured at fair value on a recurring basis.

Fair_Value_Measurements_Fair_V1

Fair Value Measurements Fair Value Measurement (Details 2) (USD $)

3 Months Ended

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Net Profit Plan liability [Member]

Net Profits Plan [Member]

6.625% Senior Notes Due 2019 [Member]

6.625% Senior Notes Due 2019 [Member]

6.50% Senior Notes Due 2021 [Member]

6.50% Senior Notes Due 2021 [Member]

6.50% Senior Notes Due 2023 [Member]

6.50% Senior Notes Due 2023 [Member]

5.0% Senior Notes Due 2024 [Member]

5.0% Senior Notes Due 2024 [Member]

Liabiliity measured at fair value using Level 3 inputs

'

'

'

'

'

'

'

'

'

'

'

Long-term Debt, Fair Value

'

'

'

$375,375,000

$374,290,000

$376,250,000

$373,625,000

$428,760,000

$422,000,000

$488,440,000

$475,315,000

Net Profits Plan

'

'

'

'

'

'

'

'

'

'

'

Discount Rate Used to Calculate Currently in Payout Liabilities

'

12.00%

'

'

'

'

'

'

'

'

'

Period Used for Price Assumptions of Strip Prices of Liabilities

'

1

'

'

'

'

'

'

'

'

'

Percent Change in Commodity Prices for Sensitivity Analysis

'

5.00%

'

'

'

'

'

'

'

'

'

Sensitivity Analysis Change in Liability, Due to Change in Commodity Prices

'

5,000,000

'

'

'

'

'

'

'

'

'

Percent Change in Discount Rate for Sensitivity Analysis

'

1.00%

'

'

'

'

'

'

'

'

'

Sensitivity Analysis Decrease in Liability Due to Change in Discount Rate

'

2,000,000

'

'

'

'

'

'

'

'

'

Cash Payments Made or Accrued under Profit Sharing Plan Related to Divested Property

'

'

217,000

'

'

'

'

'

'

'

'

Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]

'

'

'

'

'

'

'

'

'

'

'

Beginning balance

'

56,985,000

'

'

'

'

'

'

'

'

'

Net increase in liability

'

1,707,000

[1]

'

'

'

'

'

'

'

'

'

Net settlements

'

-3,483,000

[1],[2]

'

'

'

'

'

'

'

'

'

Transfers in (out) of Level 3

'

0

'

'

'

'

'

'

'

'

'

Ending balance

'

$55,209,000

'

'

'

'

'

'

'

'

'

Proved Oil and Gas Properties

'

'

'

'

'

'

'

'

'

'

'

Discount Rate Used for Fair Value of Oil and Gas Properties

12.00%

'

'

'

'

'

'

'

'

'

'

Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast

5

5

'

'

'

'

'

'

'

'

'

[1]

Net changes in the Companybs Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item of the accompanying statements of operations

[2]

Settlements represent cash payments made or accrued under the Net Profits Plan. The Company accrued or made cash payments under the Net Profits Plan of $217,000 relating to divestiture proceeds for the three months ended MarchB 31, 2014