SM Energy (SM) 10-K 19 Feb 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 12, 2014	Jun. 28, 2013
Document and Entity Information [Abstract]	'	'	'
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-K	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Amendment Flag	'false	'	'
Common Stock, Shares, Outstanding	'	67,056,441	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Public Float	'	'	$3,929,174,218.54

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
ASSETS	'	'
Cash and cash equivalents	$282,248	$5,926
Accounts receivable (Note 2)	318,371	254,805
Refundable income taxes	4,630	3,364
Prepaid expenses and other	9,944	30,017
Derivative asset	21,559	37,873
Deferred income taxes	10,749	8,579
Total current assets	647,501	340,564
Land	1,857	1,845
Proved oil and gas properties	5,637,462	5,401,684
Less - accumulated depletion, depreciation, and amortization	-2,583,698	-2,376,170
Unproved oil and gas properties	271,100	175,287
Wells in progress	279,654	273,928
Materials inventory, at lower of cost or market	15,950	13,444
Oil and gas properties held for sale, net of accumulated depletion, depreciation and amortization of $7,390 in 2013 and $20,676 in 2012	19,072	33,620
Other property and equipment, net of accumulated depreciation of $28,775 in 2013 and $22,442 in 2012	218,395	153,559
Total property and equipment, net	3,859,792	3,677,197
Derivative asset	30,951	16,466
Restricted cash	96,713	86,773
Other noncurrent assets	70,208	78,529
Total other noncurrent assets	197,872	181,768
Total Assets	4,705,165	4,199,529
LIABILITIES	'	'
Accounts payable and accrued expenses (note 2)	606,751	525,627
Derivative liabilities	26,380	8,999
Other current liabilities	6,000	6,920
Total current liabilities	639,131	541,546
Revolving credit facility	0	340,000
Senior Notes (note 5)	1,600,000	1,100,000
Asset retirement obligation	115,659	112,912
Asset retirement obligation associated with oil and gas properties held for sale	3,033	1,393
Net Profits Plan liability	56,985	78,827
Deferred income taxes; Net, non-current	650,125	537,383
Derivative liabilities	4,640	6,645
Other noncurrent liabilities	28,771	66,357
Total noncurrent liabilities	2,459,213	2,243,517
Commitments and contingencies (note 6)	'	'
STOCKHOLDERS' EQUITY	'	'
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 67,078,853 shares in 2013 and 66,245,816 shares in 2012; outstanding, net of treasury shares: 67,056,441 shares in 2013 and 66,195,235 shares in 2012	671	662
Additional paid-in capital	257,720	233,642
Treasury stock, at cost: 22,412 shares in 2013 and 50,581 shares in 2012	-823	-1,221
Retained earnings	1,354,669	1,190,397
Accumulated other comprehensive loss	-5,416	-9,014
Total stockholders' equity	1,606,821	1,414,466
Total Liabilities and Stockholders' Equity	$4,705,165	$4,199,529

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS Parenthetical (USD $)	Dec. 31, 2013	Dec. 31, 2012
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$2,583,698,000	$2,376,170,000
Common Stock, Par Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	67,078,853	66,245,816
Common Stock, Shares, Outstanding	67,056,441	66,195,235
Treasury Stock, Shares	22,412	50,581
Assets Held-for-sale [Member]	'	'
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	7,390,000	20,676,000
Other Capitalized Property Plant and Equipment [Member]	'	'
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$28,775,000	$22,442,000

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Operating revenues and other income:	'		'		'
Oil, gas, and NGL production revenue	$2,199,550		$1,473,868		$1,332,392
Realized hedge (loss) gain	-1,777		3,866		-20,707
Gain (loss) on divestiture activity	27,974		-27,018		220,676
Marketed gas system revenue	60,039		52,808		69,898
Other operating revenue	7,588		1,578		1,059
Total operating revenues and other income	2,293,374		1,505,102		1,603,318
Operating Expenses	'		'		'
Oil, gas, and NGL production expense	597,045		391,872		290,111
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	822,872		727,877		511,103
Exploration	74,104		90,248		53,537
Impairment of proved properties	172,641		208,923		219,037
Abandonment and impairment of unproved properties	46,105		16,342		7,367
General and administrative	149,551		119,815		118,526
Change in Net Profits Plan liability	-21,842		-28,904		-25,477
Derivative gain	-3,080	[1]	-55,630	[1]	-37,086	[1]
Marketed gas system expense	57,647		47,583		64,249
Other operating expense	30,076		6,993		17,567
Total operating expenses	1,925,119		1,525,119		1,218,934
Income (loss) from operations	368,255		-20,017		384,384
Nonoperating income (expense):	'		'		'
Interest income	67		220		466
Interest expense	-89,711		-63,720		-45,849
Income (loss) before income taxes	278,611		-83,517		339,001
Income tax (expense) benefit	-107,676		29,268		-123,585
Net income (loss)	$170,935		($54,249)		$215,416
Basic weighted-average common shares outstanding	66,615		65,138		63,755
Diluted weighted-average common shares outstanding	67,998		65,138		67,564
Basic net income (loss) per common share	$2.57		($0.83)		$3.38
Diluted net income (loss) per common share	$2.51		($0.83)		$3.19
[1]	Total derivative gain is reported in the derivative gain line item on the consolidated statements of cash flows within net cash provided by operating activities.

CONSOLIDATED_STATEMENT_OF_COMP

CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Net income (loss)	$170,935,000		($54,249,000)		$215,416,000
Reclassification to earnings	1,115,000		-2,264,000		12,997,000
Pension liability adjustment	2,483,000	[1]	-2,470,000	[1]	-1,795,000	[1]
Total other comprehensive income (loss), net of tax	3,598,000		-4,734,000		11,202,000
Total comprehensive income (loss)	174,533,000		-58,983,000		226,618,000
General and Administrative Expense [Member]	'		'		'
Pension liability adjustment	($768,000)		($487,000)		($262,000)
[1]	mounts are reclassified to General and administrative expense on the Company's consolidated statements of operations. The net of tax effect of the reclassification was approximately $768,000 in 2013. The accompan

CONSOLIDATED_STATEMENTS_OF_STO

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $)	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
In Thousands, except Share data, unless otherwise specified
Balances at Dec. 31, 2010	$1,218,526	$634	$191,674	($423)	$1,042,123	($15,482)
Balances (in shares) at Dec. 31, 2010	'	63,412,800	'	102,635	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'
Net income (loss)	215,416	'	'	'	215,416	'
Other comprehensive income (loss)	11,202	'	'	'	'	11,202
Cash dividends, $ 0.10 per share	-6,382	'	'	'	-6,382	'
Issuance of common stock under Employee Stock Purchase Plan	2,300	0	2,300	'	'	'
Issuance of common stock under Employee Stock Purchase Plan (in shares)	'	41,358	'	'	'	'
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings	-9,973	3	-9,976	'	'	'
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings (in shares)	'	278,773	'	'	'	'
Issuance of common stock upon stock option exercises	5,027	4	5,023	'	'	'
Issuance of common stock upon stock option exercises (in shares)	'	412,551	'	'	'	'
Stock-based compensation expense	26,824	'	27,945	-1,121	'	'
Stock-based compensation expense, Shares	'	0	'	21,568	'	'
Balances at Dec. 31, 2011	1,462,940	641	216,966	-1,544	1,251,157	-4,280
Balances (in shares) at Dec. 31, 2011	'	64,145,482	'	81,067	'	'
Common Stock, Dividends, Per Share, Declared	$0.10	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'
Net income (loss)	-54,249	'	'	'	-54,249	'
Other comprehensive income (loss)	-4,734	'	'	'	'	-4,734
Cash dividends, $ 0.10 per share	-6,511	'	'	'	-6,511	'
Issuance of common stock under Employee Stock Purchase Plan	2,776	1	2,775	'	'	'
Issuance of common stock under Employee Stock Purchase Plan (in shares)	'	66,485	'	'	'	'
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings	-21,622	9	-21,631	'	'	'
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings (in shares)	'	929,375	'	'	'	'
Issuance of common stock upon stock option exercises	3,040	2	3,038	'	'	'
Issuance of common stock upon stock option exercises (in shares)	'	240,368	'	'	'	'
Conversion of 3.50% Senior Convertible Notes to common stock, including income tax benefit of conversion	2,641	9	2,632	'	'	'
Conversion of 3.50% Senior Convertible Notes to common stock, including income tax benefit of conversion (in shares)	'	864,106	'	'	'	'
Stock-based compensation expense	30,185	'	29,862	323	'	'
Stock-based compensation expense, Shares	'	0	'	30,486	'	'
Balances at Dec. 31, 2012	1,414,466	662	233,642	-1,221	1,190,397	-9,014
Balances (in shares) at Dec. 31, 2012	'	66,245,816	'	50,581	'	'
Common Stock, Dividends, Per Share, Declared	$0.10	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'
Net income (loss)	170,935	'	'	'	170,935	'
Other comprehensive income (loss)	3,598	'	'	'	'	3,598
Cash dividends, $ 0.10 per share	-6,663	'	'	'	-6,663	'
Issuance of common stock under Employee Stock Purchase Plan	3,672	1	3,671	'	'	'
Issuance of common stock under Employee Stock Purchase Plan (in shares)	'	77,427	'	'	'	'
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings	-16,220	5	-16,225	'	'	'
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings (in shares)	'	526,852	'	'	'	'
Issuance of common stock upon stock option exercises	3,186	3	3,183	'	'	'
Issuance of common stock upon stock option exercises (in shares)	'	228,758	'	'	'	'
Stock-based compensation expense	32,347	'	31,949	398	'	'
Stock-based compensation expense, Shares	'	0	'	28,169	'	'
Other income tax benefit	1,500	'	1,500	'	'	'
Balances at Dec. 31, 2013	$1,606,821	$671	$257,720	($823)	$1,354,669	($5,416)
Balances (in shares) at Dec. 31, 2013	'	67,078,853	'	22,412	'	'

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Net income (loss)	$170,935,000		($54,249,000)		$215,416,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:	'		'		'
(Gain) loss on divestiture activity	-27,974,000		27,018,000		-220,676,000
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	822,872,000		727,877,000		511,103,000
Exploratory dry hole expense	5,846,000		20,861,000		277,000
Impairment of proved properties	172,641,000		208,923,000		219,037,000
Abandonment and impairment of unproved properties	46,105,000		16,342,000		7,367,000
Stock-based compensation expense	32,347,000		30,185,000		26,824,000
Change in Net Profits Plan liability	-21,842,000		-28,904,000		-25,477,000
Derivative gain	-3,080,000		-55,630,000		-37,086,000
Derivative cash settlement gain (loss)	22,062,000	[1]	44,264,000	[1]	-25,671,000	[1]
Amortization of debt discount and deferred financing costs	5,390,000		6,769,000		18,299,000
Deferred income taxes	105,555,000		-29,638,000		123,789,000
Plugging and abandonment	-9,946,000		-2,856,000		-5,849,000
Other	2,775,000		527,000		-6,027,000
Changes in current assets and liabilities:	'		'		'
Accounts receivable	-78,494,000		-21,389,000		-41,998,000
Refundable income taxes	-1,266,000		2,217,000		2,901,000
Prepaid expenses and other	1,364,000		-1,484,000		16,376,000
Accounts payable and accrued expenses	93,224,000		31,136,000		-18,073,000
Net cash provided by operating activities	1,338,514,000		921,969,000		760,532,000
Cash flows from investing activities:	'		'		'
Net proceeds from sale of oil and gas properties	424,849,000		55,375,000		364,522,000
Capital expenditures	-1,553,536,000		-1,507,828,000		-1,633,093,000
Acquisition of proved and unproved oil and gas properties	-61,603,000		-5,773,000		0
Receipts from restricted cash related to 1031 exchange	-1,754,000		0		0
Other	-859,000		893,000		3,661,000
Net cash used in investing activities	-1,192,903,000		-1,457,333,000		-1,264,910,000
Cash flows from financing activities:	'		'		'
Proceeds from credit facility	1,203,000,000		1,609,000,000		322,000,000
Repayment of credit facility	-1,543,000,000		-1,269,000,000		-370,000,000
Debt issuance costs related to credit facility	-3,444,000		0		-8,719,000
Net proceeds from Senior Notes	490,185,000		392,138,000		684,242,000
Repayment of 3.50% Senior Convertible Notes	0		-287,500,000		0
Proceeds from sale of common stock	6,858,000		5,816,000		7,327,000
Dividends paid	-6,663,000		-6,511,000		-6,382,000
Net share settlement from issuance of stock awards	-16,220,000		-21,622,000		-9,973,000
Other	-5,000		-225,000		0
Net cash provided by financing activities	130,711,000		422,096,000		618,495,000
Net change in cash and cash equivalents	276,322,000		-113,268,000		114,117,000
Cash and cash equivalents at beginning of period	5,926,000		119,194,000		5,077,000
Cash and cash equivalents at end of period	282,248,000		5,926,000		119,194,000
Supplemental schedule of additional cash flow information and noncash investing and financing activities:	'		'		'
Cash paid for interest, net of capitalized interest	-70,702,000		-51,328,000		-22,133,000
Net cash refunded for income taxes	204,000		1,389,000		4,046,000
Capital expenditures incurred but not yet paid	$217,820,000		$262,800,000		$214,800,000
[1]	Total derivative cash settlement gain (loss) is reported in the derivative cash settlement gain (loss) line item on the consolidated statements of cash flows within net cash provided by operating activities.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards	'
	Note 1 – Summary of Significant Accounting Policies
	Description of Operations
	SM Energy is an independent energy company engaged in the acquisition, exploration, development, and production of crude oil and condensate, gas, and NGLs in onshore North America, with a current focus on oil and liquids-rich resource plays.
	Basis of Presentation
	The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries and have been prepared in accordance with GAAP and the instructions to Form 10-K and Regulation S-X. Subsidiaries that the Company does not control are accounted for using the equity or cost methods as appropriate. Equity method investments are included in other noncurrent assets in the accompanying consolidated balance sheets (“accompanying balance sheets”). Intercompany accounts and transactions have been eliminated. In connection with the preparation of the consolidated financial statements, the Company evaluated subsequent events after the balance sheet date of December 31, 2013, through the filing date of this report. Certain prior period amounts have been reclassified to conform to the current period presentation on the accompanying balance sheets and accompanying consolidated statements of cash flows (“accompanying statements of cash flows”). The Company’s Senior Notes are combined and presented as a single line item within the accompanying balance sheets in the current year whereas they were individually presented in prior periods. The Company's total derivative gain is now presented on the accompanying statements of cash flows in cash flows from operating activities with an additional line item to adjust for the cash settlement portion.
	Use of Estimates in the Preparation of Financial Statements
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of proved oil and gas reserves, assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Estimates of proved oil and gas reserve quantities provide the basis for the calculation of depletion, depreciation, and amortization expense, impairment of proved properties, asset retirement obligations, and the Net Profits Interest Bonus Plan (“Net Profits Plan”) liability, each of which represents a significant component of the accompanying consolidated financial statements.
	Cash and Cash Equivalents
	The Company considers all liquid investments purchased with an initial maturity of three months or less to be cash equivalents. The carrying value of cash and cash equivalents approximates fair value due to the short-term nature of these instruments.
	Restricted Cash
	The Company’s restricted cash balance mainly consists of cash payments that are contractually restricted to be used solely for development of long-term capital assets pursuant to the Company’s Acquisition and Development Agreement with Mitsui and accordingly are classified as non-current assets. Please refer to Note 12 - Acquisition and Development Agreement for additional information.
	Accounts Receivable
	The Company’s accounts receivable consist mainly of receivables from oil, gas, and NGL purchasers and from joint interest owners on properties the Company operates. For receivables from joint interest owners, the Company typically has the ability to withhold future revenue disbursements to recover non-payment of joint interest billings. Generally, the Company’s oil and gas receivables are collected within two months, and the Company has had minimal bad debts.
	Although diversified among many companies, collectability is dependent upon the financial wherewithal of each individual company and is influenced by the general economic conditions of the industry. Receivables are not collateralized. As of December 31, 2013 and 2012, the Company had no allowance for doubtful accounts recorded.
	Concentration of Credit Risk and Major Customers
	The Company is exposed to credit risk in the event of nonpayment by counterparties, a significant portion of which are concentrated in energy related industries.  The creditworthiness of customers and other counterparties is subject to regular review.  During 2013, the Company had three major customers, Regency Gas Services LLC, Anadarko, and Plains Marketing LP, which accounted for approximately 26 percent, 16 percent, and 12 percent, respectively, of total oil, gas, and NGL production revenue. During the third quarter of 2013, the Company entered into various marketing agreements with Anadarko whereby the Company is subject to certain gathering, transportation, and processing through-put commitments for up to 10 years pursuant to each contract. While Anadarko is the first purchaser under these contracts, the Company also shares the risk of non-performance by Anadarko’s counterparty purchasers. Several of Anadarko’s counterparty purchasers under these contracts are also direct purchasers of products produced by the Company. During 2012, the Company had two major customers, Regency Gas Services LLC and Plains Marketing LP, which accounted for approximately 21 percent and 13 percent, respectively, of total production revenue. During 2011, the Company had one major customer, Regency Gas Services LLC, which accounted for approximately 18 percent of total production revenue.
	The Company currently uses 10 separate counterparties for its oil, gas, and NGL commodity derivatives, all of which are participating lenders in the Company’s credit facility. Three counterparties were downgraded during 2013, but all maintain investment grade ratings. Our lowest rated counterparty carries credit ratings of BBB- and Baa2, by Standard & Poor’s and Moody’s, respectively. Per the terms of our agreement with that counterparty, the Company requires cash collateral to be posted when its portfolio of trades with that counterparty is in an overall asset position.
	The Company has accounts in the following locations with a national bank: Denver, Colorado; Houston, Texas; Midland, Texas; and Billings, Montana. The Company has accounts with a local bank in Tulsa, Oklahoma. As a result of the Anadarko Basin divestiture closing at the end of 2013, the Company had a large cash balance at December 31, 2013, which was invested in money market funds among various financial institutions. This is in line with the Company’s policy is to invest in highly-rated instruments and to limit the amount of credit exposure at each individual institution.
	Oil and Gas Producing Activities
	The Company accounts for its oil and gas exploration and development costs using the successful efforts method. Geological and geophysical costs are expensed as incurred. Exploratory well costs are capitalized pending further evaluation of whether economically recoverable reserves have been found. If economically recoverable reserves are not found, exploratory well costs are expensed as dry holes. The application of the successful efforts method of accounting requires management’s judgment to determine the proper designation of wells as either development or exploratory, which will ultimately determine the proper accounting treatment of costs of dry holes. Once a well is drilled, the determination that economic proved reserves have been discovered may take considerable time and judgment. Exploratory dry hole costs are included in cash flows from investing activities as part of capital expenditures within the accompanying statements of cash flows. The costs of development wells are capitalized whether those wells are successful or unsuccessful.
	DD&A of capitalized costs related to proved oil and gas properties is calculated on a pool-by-pool basis using the units-of-production method based upon proved reserves. The computation of DD&A takes into consideration restoration, dismantlement, and abandonment costs as well as the anticipated proceeds from salvaging equipment. As of December 31, 2013, and 2012, the estimated salvage value of the Company's equipment was $57.5 million and $64.4 million, respectively.
	Materials Inventory
	The Company’s materials inventory is primarily comprised of tubular goods to be used in future drilling operations. Materials inventory is valued at the lower of cost or market and totaled $16.0 million and $13.4 million at December 31, 2013, and 2012, respectively. There were no materials inventory write-downs for the years ended December 31, 2013, 2012, or 2011.
	Assets Held for Sale
	Any properties held for sale as of the balance sheet date have been classified as assets held for sale and are separately presented on the accompanying balance sheets at the lower of net book value or fair value less the cost to sell. The asset retirement obligation liabilities related to such properties have been reclassified to asset retirement obligations associated with oil and gas properties held for sale in the accompanying balance sheets. For additional discussion on assets held for sale, please refer to Note 3 – Divestitures and Assets Held for Sale.
	Other Property and Equipment
	Other property and equipment such as facilities, office furniture and equipment, buildings, and computer hardware and software are recorded at cost. Costs of renewals and improvements that substantially extend the useful lives of the assets are capitalized. Maintenance and repair costs are expensed when incurred. Depreciation is calculated using either the straight-line method over the estimated useful lives of the assets, which range from three to thirty years, or the unit of output method where appropriate. When other property and equipment is sold or retired, the capitalized costs and related accumulated depreciation are removed from the accounts.
	Intangible Assets
	As of December 31, 2013, and 2012, the Company had $10.8 million of intangible assets consisting of acquired water rights, which are included as other noncurrent assets in the accompanying balance sheets. All intangible assets with indefinite lives are evaluated for impairment annually or if impairment indicators arise.
	Internal-Use Software Development Costs
	The Company capitalizes certain software costs incurred during the application development stage. The application development stage generally includes software design, configuration, testing and installation activities. Training and maintenance costs are expensed as incurred, while upgrades and enhancements are capitalized if it is probable that such expenditures will result in additional functionality. Capitalized software costs are depreciated over the estimated useful life of the underlying project on a straight-line basis upon completion of the project.  As of December 31, 2013, the Company has capitalized approximately $11.2 million related to the ongoing development and implementation of accounting and operational software.
	Derivative Financial Instruments
	The Company seeks to manage or reduce commodity price risk on production by entering into derivative contracts.  The Company seeks to minimize its basis risk and indexes its oil derivative contracts to NYMEX or Argus LLS prices, its NGL derivative contracts to OPIS prices, and the majority of its gas derivative contracts to various regional index prices associated with pipelines in proximity to the Company’s areas of gas production.  For additional discussion on derivatives, please see Note 10 – Derivative Financial Instruments.
	Net Profits Plan
	The Company records the estimated fair value of expected future payments made under the Net Profits Plan as a noncurrent liability in the accompanying balance sheets. The underlying assumptions used in the calculation of the estimated liability include estimates of production, proved reserves, recurring and workover lease operating expense, transportation, production and ad valorem tax rates, present value discount factors, pricing assumptions, and overall market conditions. The estimates used in calculating the long-term liability are adjusted from period-to-period based on the most current information attributable to the underlying assumptions. Changes in the estimated liability of future payments associated with the Net Profits Plan are recorded as increases or decreases to expense in the current period as a separate line item in the accompanying consolidated statements of operations (“accompanying statements of operations”), as these changes are considered changes in estimates.
	The distribution amounts due to participants and payable in each period under the Net Profits Plan as cash compensation related to periodic operations are recognized as compensation expense and are included within general and administrative expense and exploration expense in the accompanying statements of operations. The corresponding current liability is included in accounts payable and accrued expenses in the accompanying balance sheets. This treatment provides for a consistent matching of cash expense with net cash flows from the oil and gas properties in each respective pool of the Net Profits Plan. For additional discussion, please refer to the heading Net Profits Plan in Note 7 – Compensation Plans and Note 11 – Fair Value Measurements.
	Asset Retirement Obligations
	The Company recognizes an estimated liability for future costs associated with the abandonment of its oil and gas properties. A liability for the fair value of an asset retirement obligation and corresponding increase to the carrying value of the related long-lived asset are recorded at the time a well is completed or acquired. The increase in carrying value is included in proved oil and gas properties in the accompanying balance sheets. The Company depletes the amount added to proved oil and gas property costs and recognizes expense in connection with the accretion of the discounted liability over the remaining estimated economic lives of the respective oil and gas properties. For additional discussion, please refer to Note 9 – Asset Retirement Obligations.
	Revenue Recognition
	The Company derives revenue primarily from the sale of produced oil, gas, and NGLs. Revenue is recognized when the Company’s production is delivered to the purchaser, but payment is generally received between 30 and 90 days after the date of production. No revenue is recognized unless it is determined that title to the product has transferred to the purchaser. At the end of each month, the Company estimates the amount of production delivered to the purchaser and the price the Company will receive. The Company uses knowledge of its properties and historical performance, NYMEX, OPIS, and local spot market prices, quality and transportation differentials, and other factors as the basis for these estimates.
	The Company uses the sales method of accounting for gas revenue whereby sales revenue is recognized on all gas sold to purchasers, regardless of whether the sales are proportionate to the Company’s ownership in the property. An asset or liability is recognized to the extent that there is an imbalance in excess of the remaining gas reserves on the underlying properties.
	Impairment of Proved and Unproved Properties
	Proved oil and gas property costs are evaluated for impairment and reduced to fair value, which is based on expected future discounted cash flows, when there is an indication that the carrying costs may not be recoverable. Expected future cash flows are calculated on all developed proved reserves and risk adjusted proved undeveloped, probable, and possible reserves using a discount rate and price forecasts that management believes are representative of current market conditions. The prices for oil and gas are forecasted based on 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 pricing, adjusted for basis differentials, 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. An impairment is recorded on unproved property when the Company determines that either the property will not be developed or the carrying value is not realizable.
	The Company recorded $172.6 million, $208.9 million, and $219.0 million, of proved property impairments for the years ended December 31, 2013, 2012, and 2011, respectively. The impairments in 2013 resulted from the write-down of certain Mississippian limestone assets in the Company’s Permian region due to negative engineering revisions, write-downs related to Olmos interval, dry gas assets in the South Texas & Gulf Coast region as a result of a plugging and abandonment program, and write-downs of certain underperforming assets due to the Company’s decision to no longer pursue the development of those assets. The impairments in 2012 were a result of the Company’s write-down of Wolfberry assets in its Permian region due to negative engineering revisions and the Company’s Haynesville shale assets as a result of low natural gas prices. The impairments in 2011 were related to the Company’s James Lime, Cotton Valley, and Haynesville shale assets as a result of significantly lower natural gas prices at the end of 2011.
	For the years ended December 31, 2013, 2012, and 2011, the Company recorded expense related to the abandonment and impairment of unproved properties of $46.1 million, $16.3 million, and $7.4 million, respectively. The Company's abandonment and impairment of unproved properties in 2013 was mostly related to acreage the Company no longer intends to develop in its Permian region. The Company’s abandonment and impairment of unproved properties in 2012 related to acreage that the Company no longer intended to develop in its Rocky Mountain region.
	Sales of Proved and Unproved Properties
	The partial sale of proved properties within an existing field is accounted for as normal retirement and no gain or loss on divestiture activity is recognized as long as the treatment does not significantly affect the units-of-production depletion rate. The sale of a partial interest in an individual proved property is accounted for as a recovery of cost. A gain or loss on divestiture activity is recognized in the accompanying statements of operations for all other sales of proved properties.
	The partial sale of unproved property is accounted for as a recovery of cost when substantial uncertainty exists as to the ultimate recovery of the cost applicable to the interest retained. A gain on divestiture activity is recognized to the extent that the sales price exceeds the carrying amount of the unproved property. A gain or loss on divestiture activity is recognized in the accompanying statements of operations for all other sales of unproved property. For additional discussion, please refer to Note 3 – Divestitures and Assets Held for Sale.
	Stock-Based Compensation
	At December 31, 2013, the Company had stock-based employee compensation plans that included RSUs, PSUs, restricted stock awards, and stock options issued to employees and non-employee directors, as more fully described in Note 7 - Compensation Plans. The Company records expense associated with the fair value of stock-based compensation in accordance with authoritative accounting guidance, which is based on the estimated fair value of these awards determined at the time of grant.
	Income Taxes
	The Company accounts for deferred income taxes whereby deferred tax assets and liabilities are recognized based on the tax effects of temporary differences between the carrying amounts on the financial statements and the tax basis of assets and liabilities, as measured using current enacted tax rates. These differences will result in taxable income or deductions in future years when the reported amounts of the assets or liabilities are recorded or settled, respectively. The Company records deferred tax assets and associated valuation allowances, when appropriate, to reflect amounts more likely than not to be realized based upon Company analysis.
	Earnings per Share
	Basic net income (loss) per common share is calculated by dividing net income or loss available to common stockholders by the basic weighted-average common shares outstanding for the respective period. The earnings per share calculations reflect the impact of any repurchases of shares of common stock made by the Company.
	Diluted net income (loss) per common share is calculated by dividing adjusted net income or loss 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, contingent PSUs, and shares into which the 3.50% Senior Convertible Notes were convertible. When there is a loss from continuing operations, as was the case for the year ended December 31, 2012, all potentially dilutive shares are anti-dilutive and are consequently excluded from the calculation of diluted earnings per share.
	PSUs represent the right to receive, upon settlement of the PSUs after the completion of the three-year performance period, a number of shares of the Company’s common stock that may range from zero to two times 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, which 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 Share Units Under the Equity Incentive Compensation Plan.
	The Company called for redemption of its 3.50% Senior Convertible Notes on April 2, 2012, after which the majority of the holders of the outstanding 3.50% Senior Convertible Notes elected to convert their notes. The Company issued 864,106 common shares upon conversion, and these shares were included in the calculation of basic weighted-average common shares outstanding for the year ended December 31, 2012 and all subsequent years the shares remained outstanding. Please refer to Note 5 - Long-term Debt for additional discussion. Prior to calling the 3.50% Senior Convertible Notes for redemption, the Company’s notes had a net-share settlement right giving the Company the option to irrevocably elect, by notice to the trustee under the indenture for the notes, to settle the Company’s obligation, in the event that holders of the notes elected to convert all or a portion of their notes, by delivering cash in an amount equal to each $1,000 principal amount of notes surrendered for conversion and, if applicable, at the Company’s option, shares of common stock or cash, or any combination of common stock and cash, for the amount of conversion value in excess of the principal amount. Prior to the settlement of the Company’s 3.50% Senior Convertible Notes, potentially dilutive shares associated with the conversion feature were accounted for using the treasury stock method when shares of the Company’s common stock traded at an average closing price that exceeded the $54.42 conversion price. Shares of the Company’s common stock traded at an average closing price exceeding the conversion price and were included on an adjusted weighted basis for the portion of the year ended December 31, 2012, for which they were outstanding. Shares of the Company’s common stock traded at an average closing price exceeding the $54.42 conversion price for the year ended December 31, 2011, making the 3.50% Senior Convertible Notes dilutive for that period.
	The treasury stock method is used to measure the dilutive impact of in-the-money stock options, unvested RSUs, contingent PSUs, and the 3.50% Senior Convertible Notes.
	The following table details the weighted-average dilutive and anti-dilutive securities related to stock options, RSUs, PSUs, and the 3.50% Senior Convertible Notes for the years presented:
		For the Years Ended December 31,
		2013			2012			2011
		(in thousands)
	Dilutive	1,383			—			3,809
Anti-dilutive	—			2,102			—
The following table sets forth the calculations of basic and diluted earnings per share:
	For the Years Ended December 31,
	2013				2012			2011
	(in thousands, except per share amounts)
Net income (loss)	$	170,935			$	(54,249	)	$	215,416
Basic weighted-average common shares outstanding	66,615				65,138			63,755
Add: dilutive effect of stock options, unvested RSUs, and contingent PSUs	1,383				—			2,592
Add: dilutive effect of 3.50% Senior Convertible Notes	—				—			1,217
Diluted weighted-average common shares outstanding	67,998				65,138			67,564
Basic net income (loss) per common share	$	2.57			$	(0.83	)	$	3.38
Diluted net income (loss) per common share	$	2.51			$	(0.83	)	$	3.19
Comprehensive Income (Loss)
Comprehensive income (loss) is used to refer to net income (loss) plus other comprehensive income (loss). Other comprehensive income (loss) is comprised of revenues, expenses, gains, and losses that under GAAP are reported as separate components of stockholders’ equity instead of net income (loss). Comprehensive income (loss) is presented net of income taxes in the accompanying consolidated statements of comprehensive income (loss).
The changes in the balances of components comprising other comprehensive income (loss) are presented in the following table:
	Derivative Reclassification to Earnings				Pension Liability Adjustments
	(in thousands)
For the year ended December 31, 2011
Before tax income (loss)	$	20,707			$	(2,779	)
Tax benefit (expense)	(7,710		)		984
Income (loss), net of tax	$	12,997			$	(1,795	)
For the year ended December 31, 2012
Before tax loss	$	(3,865	)		$	(3,909	)
Tax benefit	1,601				1,439
Loss, net of tax	$	(2,264	)		$	(2,470	)
For the year ended December 31, 2013
Before tax income	$	1,777			$	4,005
Tax expense	(662		)		(1,522		)
Income, net of tax	$	1,115			$	2,483
Fair Value of Financial Instruments
The Company’s financial instruments including cash and cash equivalents, accounts receivable, and accounts payable are carried at cost, which approximates fair value due to the short-term maturity of these instruments. The recorded value of the Company’s credit facility approximates its fair value as it bears interest at a floating rate that approximates a current market rate. The Company had no borrowings outstanding under its credit facility as of December 31, 2013. The Company had $340.0 million of outstanding loans under its credit facility as of December 31, 2012. The Company’s Senior Notes are recorded at cost and the respective fair values are disclosed in Note 11 - Fair Value Measurements. The Company has derivative financial instruments that are recorded at fair value. Considerable judgment is required to develop estimates of fair value. The estimates provided are not necessarily indicative of the amounts the Company would realize upon the sale or refinancing of such instruments.
Industry Segment and Geographic Information
The Company operates exclusively in the exploration and production segment of the oil and gas industry and all of the Company’s operations are conducted entirely within the United States. The Company reports as a single industry segment. The Company’s gas marketing function provides mostly internal services and acts as the first purchaser of natural gas and natural gas liquids produced by the Company in certain cases. The Company considers its marketing function as ancillary to its oil and gas producing activities. The amount of income these operations generate from marketing gas produced by third parties is not material to the Company’s results of operations, and segmentation of such activity would not provide a better understanding of the Company’s performance. However, gross revenue and expense related to marketing activities for gas produced by third parties are presented in the marketed gas system revenue and marketed gas system expense line items in the accompanying statements of operations.
Off-Balance Sheet Arrangements
The Company has not participated in transactions that generate relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance or special purpose entities (“SPEs”), which would have been established for the purpose of facilitating off-balance sheet arrangements or other contractually narrow or limited purposes. The Company has not been involved in any unconsolidated SPE transactions.
The Company evaluates its transactions to determine if any variable interest entities exist. If it is determined that SM Energy is the primary beneficiary of a variable interest entity, that entity is consolidated into SM Energy. As of December 31, 2013, all variable interest entities have been consolidated.
Recently Issued Accounting Standards
On January 1, 2013, the Company adopted new authoritative accounting guidance issued by the Financial Accounting Standards Board (“FASB”), which enhanced disclosures by requiring an entity to disclose information about netting arrangements, including rights of offset, to enable users of its financial statements to understand the effect of those arrangements on its financial position and provided clarification as to the specific instruments that should be considered in these disclosures. These pronouncements were issued to facilitate comparison between financial statements prepared on the basis of GAAP and International Financial Reporting Standards. These disclosures are effective for annual and interim reporting periods beginning on or after January 1, 2013, and are to be applied retrospectively for all comparative periods presented. The impact of retrospectively adopting these pronouncements did not have a material impact on the Company’s consolidated financial statements, but did impact the Company’s disclosures. See Note 10 - Derivative Financial Instruments for tabular presentation of the Company’s gross and net derivative positions.
On January 1, 2013, the Company adopted the presentation requirements of new authoritative accounting guidance issued by the FASB in February 2013. The purpose of the guidance was to improve the reporting of reclassifications out of accumulated other comprehensive income (loss) (“AOCIL”) by requiring entities to report the effect of significant reclassifications out of AOCIL into current year income within the respective line items in net income. The presentation of those amounts may be on the face of the financial statements or in the notes thereto. This amendment was effective prospectively for periods beginning after December 15, 2012, and the Company's financial statements and disclosures were not significantly impacted.
In February 2013, the FASB issued new authoritative accounting guidance related to the recognition and measurement of obligations arising from joint and several liability arrangements. This authoritative accounting guidance is effective for interim and annual periods beginning after December 15, 2013 and is to be applied retrospectively.  Based on its evaluation, the Company determined this guidance does not currently impact the Company’s financial statements and disclosures.
In July 2013, the FASB issued new authoritative accounting guidance related to the reporting of unrecognized tax benefits when a net operating loss carryforward, similar tax loss, or tax credit carryforward exists. The guidance states an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carry-forward, a similar tax loss, or a tax credit carry-forward, with certain exceptions. This authoritative accounting guidance is effective for interim and annual periods beginning after December 15, 2013, and is to be applied prospectively to all unrecognized tax benefits that exist at the effective date.  The Company elected to early adopt this guidance in December 2013, which does not significantly affect the Company's financial statements and related disclosures.
There are no new significant accounting standards applicable to the Company that have been issued but not yet adopted by the Company as of December 31, 2013.

Accounts_Receivable_and_Accoun

Accounts Receivable and Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2013
Accounts Receivable and Accounts Payable and Accrued Expenses [Abstract]	'
Accounts Receivable and Accounts Payable and Accrued Expenses [Text Block]	'
	Note 2 – Accounts Receivable and Accounts Payable and Accrued Expenses
	Accounts receivable are comprised of the following:
		As of December 31,
		2013		2012
		(in thousands)
	Accrued oil, gas, and NGL production revenue	$	228,169	$	160,568
	Amounts due from joint interest owners	37,517		42,740
	Acquisition and Development Agreement receivable	—		19,931
	State severance tax refunds	29,213		17,237
	Other	23,472		14,329
	Total accounts receivable	$	318,371	$	254,805
	Accounts payable and accrued expenses are comprised of the following:
		As of December 31,
		2013		2012
		(in thousands)
	Accrued capital expenditures	$	217,820	$	243,611
	Revenue and severance tax payable	87,852		65,494
	Accrued lease operating expense	29,296		28,037
	Accrued property taxes	10,401		9,478
	Joint owner advances	96,636		69,639
	Accrued compensation	71,466		35,607
	Accrued interest	40,027		25,027
	Other	53,253		48,734
	Total accounts payable and accrued expenses	$	606,751	$	525,627

Divestitures_and_Assets_Held_f

Divestitures and Assets Held for Sale	12 Months Ended
	Dec. 31, 2013
Divestitures and Assets Held for Sale Disclosure [Abstract]	'
Divestitures and Assets Held for Sale	'
	Note 3 – Divestitures and Assets Held for Sale
	2013 Divestiture Activity
	•	Mid-Continent Divestitures. In December 2013, the Company divested of certain non-strategic assets located in its Mid-Continent region, with the largest transaction being the sale of the Company’s Anadarko Basin assets. Total cash proceeds received at closing (referred throughout this report as “divestiture proceeds”) were $370.3 million. The estimated net gain on these divestitures is $29.2 million.  These divestitures are subject to normal post-closing adjustments and are expected to be finalized during the first half of 2014. A portion of one transaction was structured to qualify as a like-kind exchange under Section 1031 of the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”).
	•	Rocky Mountain Divestitures. During 2013, the Company divested of certain non-strategic assets located in its Rocky Mountain region. Total divestiture proceeds were $56.3 million. The estimated net gain on these divestitures is $10.1 million.  These divestitures are subject to normal post-closing adjustments and are expected to be finalized during the first half of 2014.
	•	Permian Divestiture. In December 2013, the Company divested of certain non-strategic assets located in its Permian region. Total divestiture proceeds were $14.5 million. The estimated net loss on this divestiture is $6.5 million.  This divestiture is subject to normal post-closing adjustments and is expected to be finalized during the first half of 2014.
	The Company recorded an immaterial write-down to fair value less estimated costs to sale for assets that were held for sale as of December 31, 2013, which was reflected in the gain (loss) on divestiture activity line item in the accompanying statements of operations. See section Assets Held for Sale below for further discussion.
	2012 Divestiture Activity
	In 2012, the Company divested of various non-strategic properties located in its Rocky Mountain and
	Mid-Continent regions. Final divestiture proceeds, after the transactions post-closed in 2013, were $57.9 million and the final net gain on these divestitures was $7.4 million.
	During 2012, the Company reclassified a portion of the assets previously held for sale to assets held and used, as the assets were no longer being actively marketed. The assets were measured at the lower of the carrying value of the assets before being classified as held for sale, adjusted for any DD&A that would have been recognized had the assets been continuously held and used, or the fair value of the assets at the date they no longer met the criteria as held for sale. As a result of this measurement, the Company recognized $1.7 million of DD&A expense and a $33.9 million loss on unsuccessful sale of properties, which is included in gain (loss) on divestiture activity in the accompanying statements of operations.
	2011 Divestiture Activity
	•	Eagle Ford Shale Divestiture. In August 2011, the Company divested of certain operated Eagle Ford shale assets located in its South Texas & Gulf Coast region. This divestiture was comprised of the Company’s entire operated acreage in LaSalle County, Texas, as well as an immaterial adjacent block of its operated acreage in Dimmit County, Texas. Total divestiture proceeds were $230.7 million. The final gain on this divestiture was $193.8 million. Please refer to Note 12 - Acquisition and Development Agreement for information on additional Eagle Ford activity in 2011.
	•	Mid-Continent Divestiture. In June 2011, the Company divested of certain non-strategic assets located in its Mid-Continent region. Total divestiture proceeds were $35.8 million. The final gain on this divestiture was $28.5 million.
	•	Rocky Mountain Divestiture. In January 2011, the Company divested of certain non-strategic assets located in its Rocky Mountain region. Total divestiture proceeds were $45.5 million. The final gain on this divestiture was $27.2 million.
	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 costs to sell. Subsequent changes to the estimated fair value less the costs to sell will impact the measurement of assets held for sale for which fair value less costs to sell is determined to be less than the carrying value of the assets.
	As of December 31, 2013, the accompanying balance sheets present $19.1 million of assets held for sale, net of accumulated depletion, depreciation, and amortization expense. A corresponding asset retirement obligation liability of $3.0 million is separately presented. The assets held for sale include the Company’s Marcellus shale assets located in Pennsylvania and other certain non-strategic assets in exploratory areas, all of which are recorded at the lesser of their carrying values or their respective fair value less estimated costs to sell. Write-downs to fair value less estimated costs to sell are reflected in the gain (loss) on divestiture activity line item in the accompanying statements of operations.
	The Company determined that neither these planned nor executed asset sales qualify for discontinued operations accounting under financial statement presentation authoritative guidance.
	Subsequent to December 31, 2013, the Company began marketing certain non-strategic assets in its Rocky Mountain region. The Company expects the closing of these asset sales will occur in the first half of 2014. These assets were not classified as held for sale as of December 31, 2013.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Note 4 – Income Taxes
	The provision for income taxes consists of the following:
			For the Years Ended December 31,
			2013				2012				2011
			(in thousands)
	Current portion of income tax expense (benefit)
	Federal		$	—			$	—			$	(1,757	)
	State		2,121				370				1,553
	Deferred portion of income tax expense (benefit)		105,555				(29,638		)		123,789
	Total income tax expense (benefit)		$	107,676			$	(29,268	)		$	123,585
	Effective tax rate		38.6		%		35		%		36.5		%
	The Company reduces its income tax payable to reflect employee stock option exercises. There was no excess income tax benefit associated with stock awards in 2013, 2012, or 2011.
	The components of the net deferred income tax liabilities are as follows:
			As of December 31,
			2013				2012
			(in thousands)
	Deferred tax liabilities:
	Oil and gas properties		$	768,463			$	678,624
	Derivative asset		9,529				15,942
	Other		1,245				6,443
	Total deferred tax liabilities		779,237				701,009
	Deferred tax assets:
	Federal and state tax net operating loss carryovers		91,788				113,522
	Net Profits Plan liability		20,913				29,233
	Stock compensation		18,820				18,026
	Other long-term liabilities		13,341				16,739
	Total deferred tax assets		144,862				177,520
	Valuation allowance		(5,001		)		(5,315		)
	Net deferred tax assets		139,861				172,205
	Total net deferred tax liabilities		639,376				528,804
	Less: current deferred income tax liabilities		(172		)		(5,442		)
	Add: current deferred income tax assets		10,921				14,021
	Non-current net deferred tax liabilities		$	650,125			$	537,383
	Current federal income tax refundable		$	4,630			$	2,511
	Current state income tax refundable		$	—			$	853
	Current state income tax payable		$	1,460			$	—
	At December 31, 2013, the Company estimated its federal net operating loss carryforward at $376.1 million, which includes unrecognized excess income tax benefits associated with stock awards of $126.7 million. The Company expects future excess benefit utilization to be recognized using the with-and-without method. The federal net operating loss carryforward begins to expire in 2031. The Company has estimated state net operating loss carryforwards of $147.5 million that expire between 2014 and 2034. The Company has federal research and development (“R&D”) credit carryforwards of $5.0 million that expire between 2028 and 2031. The Company’s valuation allowance relates to charitable contribution carryfowards, state net operating loss carryforwards, state tax credits, and state and federal income tax benefit amounts, which the Company anticipates will expire before they can be utilized. The change in the valuation allowance from 2012 to 2013 primarily reflects utilization of Oklahoma net operating losses resulting from the 2013 Anadarko Basin asset divestiture gain offset in part by a change in the Company’s position regarding anticipated utilization of cumulative net operating losses attributed to other states.
	Federal income tax expense differs from the amount 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, R&D credits, and other permanent differences, as follows:
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Federal statutory tax expense (benefit)	$	97,514			$	(29,231	)		$	118,652
	Increase (decrease) in tax resulting from:
	State tax expense (benefit) (net of federal benefit)	9,400				(992		)		6,458
	Research and development credit	—				(970		)		(4,516		)
	Change in valuation allowance	(314		)		1,524				1,627
	Statutory depletion	(154		)		(210		)		(341		)
	Other	1,230				611				1,705
	Income tax expense (benefit)	$	107,676			$	(29,268	)		$	123,585
	Acquisitions, divestitures, drilling activity, and basis differentials impacting the prices received for oil, gas, and NGLs affect apportionment of taxable income to the states where the Company owns oil and gas properties. As its apportionment factors change, the Company’s blended state income tax rate changes. This change, when applied to the Company’s total temporary differences, impacts the total income tax reported in the current year and is reflected in state taxes in the table above. Items affecting state apportionment factors are evaluated at the beginning of each year, after completion of the prior year income tax return, and when significant acquisition, divestiture or changes in drilling activity occurs during the year. Significant divestiture activity impacting the Company’s blended state rate occurred during the fourth quarter of 2013.
	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 these tax authorities for years before 2007. Federal tax law allowing for the calculation of an R&D credit was enacted in 2013, but the Company has not yet commissioned a study to calculate the credit for the 2012 or 2013 tax years. The table above excludes the impact for any credit that would be allowed under the new law in either period. 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 was notified during December 2013 the case has been received by the IRS Appeals office, but a conference had not been scheduled as of the filing date of this report. In the fourth quarter of 2013, the Company filed a federal net operating loss carryback claim along with other audit adjustments not processed during the 2013 audit, amounting to a $4.0 million refund.
	On September 13, 2013 the United States Department of the Treasury and IRS issued 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 as of December 31, 2013.
	The Company complies with authoritative accounting guidance regarding uncertain tax provisions. The entire amount of unrecognized tax benefit reported by the Company would affect its effective tax rate if recognized. Interest expense in the accompanying statements of operations includes a negligible amount associated with income taxes. In 2011, the Company also recorded a negligible amount of penalty expense associated with income taxes as a general and administrative expense. At December 31, 2013, the Company estimates the range of reasonably possible change in 2014 to the table below could be from zero to $1.4 million.
	The total amount recorded for unrecognized tax benefits is presented below:
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Beginning balance	$	2,278			$	1,961			$	807
	Additions based on tax positions related to current year	—				—				1,172
	Additions for tax positions of prior years	80				317				183
	Reductions for lapse of statute of limitations	—				—				(201		)
	Ending balance	$	2,358			$	2,278			$	1,961

LongTerm_Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Long-Term Debt	'
	Note 5 – Long-term Debt
	Revolving Credit Facility
	The Company and its lenders entered into a Fifth Amended and Restated Credit Agreement on April 12, 2013, which replaced the Company's previous credit facility. The Company incurred approximately $3.4 million in deferred financing costs associated with the amendment and extension of this credit facility. The credit facility has 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 initial borrowing base under the credit facility was $1.9 billion. On May 20, 2013, the Company's borrowing base under the credit facility was automatically reduced, by 25 percent of the aggregate principal amount of the newly-issued 2024 Notes, to $1.775 billion. The borrowing base is subject to regular semi-annual redeterminations.  On September 6, 2013, the lending group redetermined the Company's borrowing base under the credit facility and increased it to $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 bank group. The next scheduled redetermination date is April 1, 2014. Borrowings under the facility are secured by a large majority 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 limitations on dividend payments and requirements to maintain certain financial ratios, which include debt to EBITDAX, as defined by our credit agreement as the ratio of debt to 12-month trailing EBITDAX, of less than 4.0 and an adjusted current ratio, as defined by our credit agreement, of no less than 1.0.  The Company was in compliance with all financial and non-financial covenants under the credit facility as of December 31, 2013, and through the filing date of this report.
	Interest and commitment fees are accrued based on the borrowing base utilization grid below.  Eurodollar loans accrue interest at the London Interbank Offered Rate plus the applicable margin from the utilization table below, and Alternate Base Rate (“ABR”) and swingline loans accrue interest at Prime plus the applicable margin from the utilization table below.  Commitment fees are accrued on the unused portion of the aggregate commitment amount and are included in interest expense in the accompanying statements of operations.
	Borrowing Base Utilization Grid
	Borrowing Base Utilization Percentage		<25%		≥25% <50%		≥50% <75%			≥75% <90%		≥90%
	Eurodollar Loans		1.5	%	1.75	%	2	%		2.25	%	2.5	%
	ABR Loans or Swingline Loans		0.5	%	0.75	%	1	%		1.25	%	1.5	%
	Commitment Fee Rate		0.375	%	0.375	%	0.5	%		0.5	%	0.5	%
	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 February 12, 2014, December 31, 2013, and December 31, 2012:
		As of February 12, 2014			As of December 31, 2013			As of December 31, 2012
		(in millions)
	Credit facility balance	$	—		$	—		$	340
	Letters of credit (1)	$	0.8		$	0.8		$	0.8
	Available borrowing capacity	$	1,299.20		$	1,299.20		$	659.2
	(1) Letters of credit reduce the amount available under the credit facility on a dollar-for-dollar basis.
	Senior Notes
	The Senior Notes line on the accompanying balance sheets, as of December 31, 2013, and 2012, consisted of the following:
		As of December 31,
		2013			2012
		(in thousands)
	6.625% Senior Notes due 2019	$	350,000		$	350,000
	6.50% Senior Notes due 2021	350,000			350,000
	6.50% Senior Notes due 2023	400,000			400,000
	5.0% Senior Notes due 2024	500,000			—
	Total long-term debt	$	1,600,000		$	1,100,000
	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 indenture 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 the restricted payment covenant. The Company was in compliance with all covenants under its Senior Notes as of December 31, 2013, and through the filing date of this report.
	2024 Notes
	On May 20, 2013, the Company issued $500.0 million in aggregate principal amount of 5.0% Senior Notes due 2024. The 2024 Notes were issued at par and mature on January 15, 2024. The Company received net proceeds of $490.2 million after deducting fees of $9.8 million, which are being amortized as deferred financing costs over the life of the 2024 Notes. The net proceeds were used to reduce the Company’s outstanding credit facility balance.
	Prior to July 15, 2016, the Company may redeem, on one or more occasions, up to 35 percent of the aggregate principal amount of the 2024 Notes with the net cash proceeds of certain equity offerings at a redemption price of 105% of the principal amount thereof, plus accrued and unpaid interest. The Company may also redeem the 2024 Notes, in whole or in part, at any time prior to July 15, 2018, at a redemption price equal to 100 percent of the principal amount of the 2024 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date.
	On or after July 15, 2018, the Company may also redeem all or, from time to time, a portion of the 2024 Notes at the redemption prices set forth below, during the twelve-month period beginning on July 15 of each applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2018	102.5	%
	2019	101.677	%
	2020	100.833	%
	2021 and thereafter	100	%
	Additionally, 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. Pursuant to the registration rights agreement, the Company is required to file an exchange offer registration statement with the SEC with respect to its offer to exchange the 2024 Notes for substantially identical notes that are registered under the Securities Act. Under certain circumstances, the Company has agreed to file a shelf registration statement relating to the resale of the 2024 Notes in lieu of a registered exchange offer. If the registration statement related to the exchange offer is not declared effective 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.
	2023 Notes
	On June 29, 2012, the Company issued $400.0 million in aggregate principal amount of 6.50% Senior Notes due 2023. The 2023 Notes were issued at par and mature on January 1, 2023. The Company received net proceeds of $392.1 million after deducting fees of $7.9 million, which are being amortized as deferred financing costs over the life of the 2023 Notes. The net proceeds were used to reduce the Company’s outstanding credit facility balance.
	Prior to July 1, 2015, the Company may redeem, on one or more occasions, up to 35 percent of the aggregate principal amount of the 2023 Notes with the net cash proceeds of certain equity offerings at a redemption price of 106.5% of the principal amount thereof, plus accrued and unpaid interest. The Company may also redeem the 2023 Notes, in whole or in part, at any time prior to July 1, 2017, at a redemption price equal to 100 percent of the principal amount of the 2023 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date.
	On or after July 1, 2017, the Company may also redeem all or, from time to time, a portion of the 2023 Notes at the redemption prices set forth below, during the twelve-month period beginning on July 1 of each applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2017	103.25	%
	2018	102.167	%
	2019	101.083	%
	2020 and thereafter	100	%
	Additionally, on June 29, 2012, the Company entered into a registration rights agreement that provides holders of the 2023 Notes certain registration rights under the Securities Act. The Company satisfied its obligations to exchange its outstanding $400.0 million of its 2023 Notes for notes registered under the Securities Act on October 30, 2012.
	2021 Notes
	On November 8, 2011, the Company issued $350.0 million in aggregate principal amount of 6.50% Senior Notes due 2021. The 2021 Notes were issued at par and mature on November 15, 2021. The Company received net proceeds of $343.1 million after deducting fees of $6.9 million, which are being amortized as deferred financing costs over the life of the 2021 Notes. The net proceeds were used for general corporate purposes and to reduce the Company’s outstanding credit facility balance.
	Prior to November 15, 2014, the Company may redeem up to 35 percent of the aggregate principal amount of the 2021 Notes with the net cash proceeds of one or more equity offerings at a redemption price of 106.5% of the principal amount thereof, plus accrued and unpaid interest. The Company may also redeem the 2021 Notes, in whole or in part, at any time prior to November 15, 2016, at a redemption price equal to 100% of the principal amount, plus a specified make-whole premium and accrued and unpaid interest.
	The Company may also redeem all or, from time to time, a portion of the 2021 Notes on or after November 15, 2016, at the prices set forth below, during the twelve-month period beginning on November 15 of the applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2016	103.25	%
	2017	102.167	%
	2018	101.083	%
	2019 and thereafter	100	%
	Additionally, on November 8, 2011, the Company entered into a registration rights agreement that provides holders of the 2021 Notes certain registration rights for the 2021 Notes under the Securities Act. The Company satisfied its obligations to exchange its outstanding $350.0 million of its 2021 Notes for notes registered under the Securities Act on March 7, 2012.
	2019 Notes
	On February 7, 2011, the Company issued $350.0 million in aggregate principal amount of 6.625% Senior Notes due 2019. The 2019 Notes were issued at par and mature on February 15, 2019. The Company received net proceeds of $341.1 million after deducting fees of $8.9 million, which are being amortized as deferred financing costs over the life of the 2019 Notes. The net proceeds were used to repay borrowings under the Company’s credit facility, to fund the Company’s ongoing capital expenditure program, and for general corporate purposes.
	The Company may redeem the 2019 Notes, in whole or in part, at any time prior to February 15, 2015, at a redemption price equal to 100% of the principal amount, plus a specified make-whole premium and accrued and unpaid interest.
	The Company may also redeem all or, from time to time, a portion of the 2019 Notes on or after February 15, 2015, at the prices set forth below, during the twelve-month period beginning on February 15 of the applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2015	103.313	%
	2016	101.656	%
	2017 and thereafter	100	%
	Additionally, on February 7, 2011, the Company entered into a registration rights agreement that provides holders of the 2019 Notes certain registration rights for the 2019 Notes under the Securities Act. The Company satisfied its obligations to exchange its outstanding $350.0 million of its 2019 Notes for notes registered under the Securities Act on January 11, 2012.
3.50% Senior Convertible Notes
On April 2, 2012, the Company called for redemption all of its outstanding 3.50% Senior Convertible Notes. The call for redemption resulted in holders of $281.3 million aggregate principal amount electing to convert their notes. The Company settled the principal amount of all converted 3.50% Senior Convertible Notes in cash and settled the excess conversion value by issuing 864,106 shares of its common stock. The Company redeemed the remaining $6.2 million of aggregate principal amount of notes that were not converted on the redemption date at par plus accrued interest in cash. The Company used funds borrowed under its credit facility to pay the cash portion of the settlement.
Capitalized Interest
Capitalized interest costs for the Company for the years ended December 31, 2013, 2012, and 2011, were $11.0 million, $12.1 million, and $10.8 million, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Note 6 – Commitments and Contingencies
	Commitments
	The Company has entered into various agreements, which include drilling rig contracts of $65.7 million, gathering, processing, and transportation through-put commitments of $1.1 billion, office leases, including maintenance, of $69.4 million, and other miscellaneous contracts and leases of $7.6 million. The annual minimum payments for the next five years and total minimum lease payments thereafter are presented below:
	Years Ending December 31,	(in thousands)
	2014	$	179,118
	2015	147,119
	2016	144,438
	2017	132,559
	2018	128,418
	Thereafter	481,947
	Total	$	1,213,599
	The Company has gathering, processing, and transportation through-put commitments with various parties that require delivery of a fixed determinable quantity of product. The aggregate minimum commitment to deliver is 1,807 Bcf of natural gas and 53 MMBbl of oil. These contracts expire at various dates through 2023 and the total amount of the commitment is approximately $1.1 billion. The Company will be required to make periodic deficiency payments for any shortfalls in delivering the minimum volume commitments. As of the filing date of this report, the Company does not expect to incur any material shortfalls.
	The Company leases office space under various operating leases with terms extending as far as May 31, 2024. During the third quarter of 2013, the Company entered into an office lease with an initial term of 12 years and minimum lease payments of $12.9 million over the term beginning on the commencement date, which is anticipated to be in the second quarter of 2014. Rent expense for 2013, 2012, and 2011, was $5.7 million, $5.4 million, and $3.7 million, respectively. The Company also leases office equipment under various operating leases.
	In addition to the amounts in the above table, the Company has committed to pay its portion of the development of infrastructure in its outside operated Eagle Ford shale play. The system owners unanimously approved budgeted costs for 2014, of which the Company is committed to pay approximately $33.0 million for the upcoming year.
	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 January 27, 2011, 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 issues 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 substantive discovery yet to be conducted, 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 its assets that were subject to this matter, and the buyer assumed any such liabilities related to such properties.
	In an unrelated matter, as of and for the year ended December 31, 2013, other operating expenses includes $23.1 million related to an agreed clarification concerning royalty payment provisions of various leases on certain South Texas & Gulf Coast acreage. As of December 31, 2013, $9.6 million is included in accounts payable and accrued expenses as $13.5 million was paid in 2013.

Compensation_Plans

Compensation Plans	12 Months Ended
	Dec. 31, 2013
Compensation Related Costs [Abstract]	'
Compensation Plans	'
	Note 7 – Compensation Plans
	Cash Bonus Plan
	The Company has a cash bonus plan based on a performance measurement framework whereby selected eligible employee participants may be awarded an annual cash bonus. The plan document provides that no participant may receive an annual bonus under the plan of more than 200 percent of his or her base salary. As the plan is currently administered, any awards under the plan are based on Company and regional performance and are then further refined by individual performance. The Company accrues cash bonus expense based upon the Company’s current year performance. Included in general and administrative expense, lease operating expense, and exploration expense in the accompanying statements of operations are $41.8 million, $16.3 million, and $23.9 million of cash bonus expense related to the specific performance years ended December 31, 2013, 2012, and 2011, respectively.
	Equity Plan
	There are several components to the Company’s Equity Plan that are described in this section. Various types of equity awards have been granted by the Company in different periods.
	As of December 31, 2013, 3.8 million shares of common stock remained available for grant under the Equity Plan. The issuance of a direct share benefit such as a share of common stock, a stock option, a restricted share, a RSU, or a PSU counts as one share against the number of shares available to be granted under the Equity Plan. Each PSU has the potential to count as two shares against the number of shares available to be granted under the Equity Plan based on the final performance multiplier. Stock options were issued out of the St. Mary Land & Exploration Company Stock Option Plan and the St. Mary Land & Exploration Company Incentive Stock Option Plan, both predecessors to the Equity Plan.
	Performance Share Units Under the Equity Incentive Compensation Plan
	The Company grants PSUs to eligible employees as a part of its equity compensation program. The PSU factor is based on the Company’s performance after completion of a three-year performance period. The performance criteria for the PSUs are based on a combination of the Company’s annualized Total Shareholder Return (“TSR”) for the performance period and the relative performance of the Company’s TSR compared with the annualized TSR of certain peer companies for the performance period. PSUs are recognized as general and administrative and exploration expense over the vesting period of the award.
	The fair value of PSUs was measured at the grant date with a stochastic process method using the Geometric Brownian Motion Model (“GBM Model”). A stochastic process is a mathematically defined equation that can create a series of outcomes over time. These outcomes are not deterministic in nature, which means that by iterating the equations multiple times, different results will be obtained for those iterations. In the case of the Company’s PSUs, the Company cannot predict with certainty the path its stock price or the stock prices of its peers will take over the three-year performance period. By using a stochastic simulation, the Company can create multiple prospective stock pathways, statistically analyze these simulations, and ultimately make inferences regarding the most likely path the stock price will take. As such, because future stock prices are stochastic, or probabilistic with some direction in nature, the stochastic method, specifically the GBM Model, is deemed an appropriate method by which to determine the fair value of the PSUs. Significant assumptions used in this simulation include the Company’s expected volatility, dividend yield, and risk-free interest rate based on U.S. Treasury yield curve rates with maturities consistent with a three-year vesting period, as well as the volatilities and dividend yields for each of the Company’s peers.
	Total expense recorded for PSUs was $16.8 million, $18.2 million, and $19.7 million for the years ended December 31, 2013, 2012, and 2011, respectively. As of December 31, 2013, there was $18.8 million of total unrecognized expense related to PSUs, which is being amortized through 2016.
	A summary of the status and activity of non-vested PSUs is presented in the following table:
		For the Years Ended December 31,
		2013						2012					2011
		PSUs		Weighted-Average Grant-Date Fair Value				PSUs			Weighted-Average Grant-Date Fair Value		PSUs		Weighted-Average Grant-Date Fair Value
	Non-vested at beginning of year(1)	669,308		$	63.91			885,894			$	57.52	1,110,666		$	39.48
	Granted(1)	274,831		$	64.13			314,853			$	51.98	266,282		$	91.45
	Vested(1)	(345,005	)	$	60.06			(493,679	)		$	44.72	(364,172	)	$	35.74
	Forfeited(1)	(26,665	)	$	69.74			(37,760	)		$	65.35	(126,882	)	$	33.32
	Non-vested at end of year(1)	572,469		$	66.07			669,308			$	63.91	885,894		$	57.52
	-1	The number of awards assumes a one multiplier. The final number of shares of common stock issued may vary depending on the ending three-year performance multiplier, which ranges from zero to two.
	The fair value of the PSUs granted in 2013, 2012, and 2011 was $17.6 million, $16.4 million, and $24.3 million for the 2013, 2012, and 2011 grants, respectively. The PSUs granted in 2013 will remain unvested until the third anniversary date of their issuance, at which time they will fully vest. The PSUs granted in 2012 will vest 1/3 on each of the first three anniversary dates of their issuance. PSUs granted prior to 2012 vest 1/7th, 2/7ths, and 4/7ths, respectively, on the first three anniversary dates of their issuances.
	The total fair value of PSUs that vested during the years ended December 31, 2013, 2012, and 2011 was $20.7 million, $22.1 million, and $13.0 million, respectively.
	During the year ended December 31, 2013, the Company settled PSUs that were granted in 2010, and which had earned a 1.725-times multiplier, by issuing a net 387,461 shares of the Company’s common stock in accordance with the terms of the PSU awards. The Company and the majority of grant participants mutually agreed to net share settle the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, 200,050 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those PSUs for 2013.
	During the year ended December 31, 2012, the Company settled PSUs that were granted in 2009, which earned a 2.0-times multiplier, by issuing a net 812,562 shares of the Company’s common stock in accordance with the terms of the PSU awards. The Company and the majority of grant participants mutually agreed to net share settle the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, 406,866 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those PSUs for 2012.
	During the year ended December 31, 2011, the Company settled PSUs that were granted in 2008, and which had earned a 0.8-times multiplier, by issuing a net 206,468 shares of the Company’s common stock in accordance with the terms of the PSU awards. The Company and the majority of grant participants mutually agreed to net share settle the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, 98,955 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those PSUs for 2011.
	Restricted Stock Units Under the Equity Incentive Compensation Plan
	The Company grants RSUs to eligible employees as a part of its equity incentive compensation program. Restrictions and vesting periods for the awards are determined by the Compensation Committee of the Board of Directors and are set forth in the award agreements. Each RSU represents a right for one share of the Company’s common stock to be delivered upon settlement of the award at the end of a specified period. RSUs are recognized as general and administrative and exploration expense over the vesting period of the award.
	The total expense associated with RSUs for the years ended December 31, 2013, 2012, and 2011, was $13.1 million, $9.8 million, and $5.3 million, respectively. As of December 31, 2013, there was $19.3 million of total unrecognized expense related to unvested RSU awards, which is being amortized through 2016. The Company records compensation expense associated with the issuance of RSUs based on the fair value of the awards as of the date of grant. The fair value of an RSU is equal to the closing price of the Company’s common stock on the day of grant.
	A summary of the status and activity of non-vested RSUs is presented below:
		For the Years Ended December 31,
		2013						2012					2011
		RSUs		Weighted-				RSUs			Weighted-		RSUs		Weighted-
				Average							Average				Average
				Grant-Date							Grant-Date				Grant-Date
				Fair Value							Fair Value				Fair Value
	Non-vested at beginning of year	496,244		$	51.81			308,877			$	44.33	333,359		$	31.16
	Granted	329,939		$	60.01			379,332			$	49.47	98,952		$	72.69
	Vested	(207,376	)	$	49.73			(166,672	)		$	32.72	(105,820	)	$	30.61
	Forfeited	(38,376	)	$	54.37			(25,293	)		$	51.06	(17,614	)	$	36.8
	Non-vested at end of year	580,431		$	57.05			496,244			$	51.81	308,877		$	44.33
	The fair value of RSUs granted in 2013, 2012, and 2011 was $19.8 million, $18.8 million, and $7.2 million, respectively. The RSUs granted in 2013 and 2012 will vest 1/3 on each of the first three anniversary dates of the awards. RSUs granted prior to 2012 vest 1/7th, 2/7ths, and 4/7ths, respectively, on the first three anniversary dates of their issuances.
	The total fair value of RSUs that vested during the years ended December 31, 2013, 2012, and 2011, was $10.3 million, $5.4 million, and $3.2 million, respectively.
	During the years ended December 31, 2013, 2012, and 2011, the Company settled 207,378, 166,670, and 105,820 RSUs, respectively. The Company and the majority of grant participants mutually agreed to net share settle the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, the Company issued net shares of common stock of 139,391, 116,813, and 72,305 for 2013, 2012, and 2011, respectively. The remaining 67,987, 49,857, and 33,515 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon the delivery of the shares underlying those RSUs for 2013, 2012, and 2011, respectively.
	Stock Option Grants Under the Equity Incentive Compensation Plan
	The Company has previously granted stock options under the St. Mary Land & Exploration Company Stock Option Plan and the St. Mary Land & Exploration Company Incentive Stock Option Plan. The last issuance of stock options occurred on December 31, 2004. Stock options to purchase shares of the Company’s common stock had been granted to eligible employees and members of the Board of Directors. All options granted under the option plans were granted at exercise prices equal to the respective closing market price of the Company’s underlying common stock on the grant dates. All stock options granted under the option plans are exercisable for a period of up to ten years from the date of grant. As of December 31, 2013, there was no unrecognized compensation expense related to stock option awards.
	A summary of activity associated with the Company’s Stock Option Plans during the last three years is presented in the following table:
				Weighted -
				Average				Aggregate
				Exercise				Intrinsic
		Shares		Price				Value
	For the year ended December 31, 2011
	Outstanding, start of year	920,765		$	13.11
	Exercised	(412,551	)	$	12.19			$	24,359,240
	Forfeited	—		$	—
	Outstanding, end of year	508,214		$	13.86			$	30,109,110
	Vested and exercisable at end of year	508,214		$	13.86			$	30,109,110
	For the year ended December 31, 2012
	Outstanding, start of year	508,214		$	13.86
	Exercised	(240,368	)	$	12.65			$	11,842,575
	Forfeited	—		$	—
	Outstanding, end of year	267,846		$	14.95			$	9,983,177
	Vested and exercisable at end of year	267,846		$	14.95			$	9,983,177
	For the year ended December 31, 2013
Outstanding, start of year	267,846		$	14.95
Exercised	(228,758	)	$	13.92			$	12,326,994
Forfeited	—		$	—
Outstanding, end of year	39,088		$	20.87			$	2,432,837
Vested and exercisable at end of year	39,088		$	20.87			$	2,432,837
A summary of additional information related to options outstanding as of December 31, 2013, follows:
			Options Outstanding and Exercisable
			Number			Weighted-
			Of Options			Average
			Outstanding			Remaining
Exercise			and			Contractual
Price(1)			Exercisable			Life (in years)
$	20.87		39,088			1
Total			39,088
(1) Exercise price is equal to the weighted average exercise price.
The fair value of options was measured at the date of grant using the Black-Scholes-Merton option-pricing model.
Cash flows resulting from excess tax benefits are classified as part of cash flows from financing activities. Excess tax benefits are realized tax benefits from tax deductions for vested RSUs, settled PSUs, and exercised options in excess of the deferred tax asset attributable to stock compensation costs for such equity awards. The Company recorded no excess tax benefits for the years ended December 31, 2013, 2012, and 2011. Cash received from exercises under all share-based payment arrangements for the years ended December 31, 2013, 2012, and 2011, was $3.2 million, $3.0 million, and $5.0 million, respectively.
Director Shares
In 2013, 2012, and 2011, the Company issued 28,169, 30,486, and 21,568 shares, respectively, of the Company’s common stock held as treasury shares to its non-employee directors pursuant to the Company’s Equity Plan. The Company recorded compensation expense related to these issuances of $1.4 million, $1.3 million, and $1.2 million for the years ended December 31, 2013, 2012, and 2011, respectively.
Employee Stock Purchase Plan
Under the Company’s Employee Stock Purchase Plan (“ESPP”), eligible employees may purchase shares of the Company’s common stock through payroll deductions of up to 15 percent of eligible compensation, without accruing in excess of $25,000 in fair market value from purchases for each calendar year. The purchase price of the stock is 85 percent of the lower of the fair market value of the stock on the first or last day of the purchase period. All shares issued under the ESPP on or after December 31, 2011, have no minimum restriction period. The ESPP is intended to qualify under Section 423 of the IRC. The Company has 1.2 million shares available under the ESPP for issuance as of December 31, 2013. Shares issued under the ESPP totaled 77,427 in 2013, 66,485 in 2012, and 41,358 in 2011. Total proceeds to the Company for the issuance of these shares were $3.7 million in 2013, $2.8 million in 2012, and $2.3 million in 2011.
The fair value of ESPP shares was measured at the date of grant using the Black-Scholes-Merton option-pricing model. Expected volatility was calculated based on the Company’s historical daily common stock price, and the risk-free interest rate is based on U.S. Treasury yield curve rates with maturities consistent with a six month vesting period.
The fair value of ESPP shares issued during the periods reported were estimated using the following weighted-average assumptions:
	For the Years Ended December 31,
	2013		2012			2011
Risk free interest rate	0.1	%	0.1	%		0.2	%
Dividend yield	0.2	%	0.2	%		0.2	%
Volatility factor of the expected market
price of the Company’s common stock	41.1	%	47.8	%		36.3	%
Expected life (in years)	0.5		0.5			0.5
The Company expensed $1.1 million, $948,000, and $682,000 for the years ended December 31, 2013, 2012, and 2011, respectively, based on the estimated fair value of grants.
401(k) Plan
The Company has a defined contribution pension plan (the “401(k) Plan”) that is subject to the Employee Retirement Income Security Act of 1974. The 401(k) Plan allows eligible employees to contribute a maximum of 60 percent of their base salaries up to the contribution limits established under the IRC. The Company matches each employee’s contribution up to six percent of the employee’s base salary and may make additional contributions at its discretion. Beginning in 2014, the Company will also match employee contributions up to six percent of the employee's bonus paid pursuant to the Company's cash bonus plan. The Company’s matching contributions to the 401(k) Plan were $4.2 million, $3.5 million, and $2.9 million for the years ended December 31, 2013, 2012, and 2011, respectively. No discretionary contributions were made by the Company to the 401(k) Plan for any of these years.
Net Profits Plan
Under the Company’s Net Profits Plan, all oil and gas wells that were completed or acquired during each year were designated within a specific pool. Key employees recommended by senior management and designated as participants by the Compensation Committee of the Company’s Board of Directors and employed by the Company on the last day of that year became entitled to payments under the Net Profits Plan after the Company has received net cash flows returning 100 percent of all costs associated with that pool. Thereafter, 10 percent of future net cash flows generated by the pool are allocated among the participants and distributed at least annually. The portion of net cash flows from the pool to be allocated among the participants increases to 20 percent after the Company has recovered 200 percent of the total costs for the pool, including payments made under the Net Profits Plan at the 10 percent level. In December 2007, the Board of Directors discontinued the creation of new pools under the Net Profits Plan. As a result, the 2007 pool was the last Net Profits Plan pool established by the Company.
Cash payments made or accrued under the Net Profits Plan that have been recorded as either general and administrative expense or exploration expense are detailed in the table below:
	For the Years Ended December 31,
	2013			2012				2011
	(in thousands)
General and administrative expense	$	13,734		$	15,565			$	19,326
Exploration expense	1,310			1,751				2,091
Total	$	15,044		$	17,316			$	21,417
Additionally, the Company made or accrued cash payments under the Net Profits Plan of $10.3 million, $2.3 million, and $6.3 million for the years ended December 31, 2013, 2012, and 2011, respectively, as a result of divestiture proceeds. The cash payments are accounted for as a reduction in the gain (loss) on divestiture activity line item in the accompanying statements of operations.
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. The amount recorded as an expense or benefit associated with the change in the estimated liability is not allocated to general and administrative 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 general and administrative expense. The amount that would be allocated to exploration expense is minimal in comparison. 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	12 Months Ended
	Dec. 31, 2013
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]	'
Pension Benefits	'
	Note 8 – Pension Benefits
	The Company has a non-contributory defined benefit 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”).
	Obligations and Funded Status for Both Pension Plans
	The Company recognizes the funded status, (i.e. the difference between the fair value of plan assets and the projected benefit obligation) of the Company’s Pension Plans in the accompanying balance sheets as either an asset or a liability and recognizes a corresponding adjustment to accumulated other comprehensive income, net of tax. The projected benefit obligation is the actuarial present value of the benefits earned to date by plan participants based on employee service and compensation including the effect of assumed future salary increases. The accumulated benefit obligation uses the same factors as the projected benefit obligation but excludes the effects of assumed future salary increases. The Company’s measurement date for plan assets and obligations is December 31.
		For the Years Ended December 31,
		2013				2012
		(in thousands)
	Change in benefit obligation:
	Projected benefit obligation at beginning of year	$	40,237			$	29,480
	Service cost	6,291				4,934
	Interest cost	1,627				1,374
	Plan amendments	—				—
	Actuarial loss (gain)	(1,577		)		5,467
	Benefits paid	(3,293		)		(1,018		)
	Projected benefit obligation at end of year	43,285				40,237
	Change in plan assets:
	Fair value of plan assets at beginning of year	20,254				13,940
	Actual return on plan assets	2,726				1,952
	Employer contribution	4,971				5,380
	Benefits paid	(3,293		)		(1,018		)
	Fair value of plan assets at end of year	24,658				20,254
	Funded status at end of year	$	(18,627	)		$	(19,983	)
	The Company’s underfunded status for the Pension Plans for the years ended December 31, 2013 and 2012, is $18.6 million and $20.0 million, respectively, and is recognized in the accompanying balance sheets as a portion of other noncurrent liabilities. No plan assets of the Qualified Pension Plan were returned to the Company during the fiscal year ended December 31, 2013. There are no plan assets in the Nonqualified Pension Plan. The plan was amended in 2011 to increase the vesting percent to 40 percent after attaining two years of service and increasing by 20 percent per year until fully vested.
	Information for Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets for Both Plans
		As of December 31,
		2013				2012
		(in thousands)
	Projected benefit obligation	$	43,285			$	40,237
	Accumulated benefit obligation	$	32,396			$	29,437
	Less: Fair value of plan assets	(24,658		)		(20,254		)
	Underfunded accumulated benefit obligation	$	7,738			$	9,183
	Pension expense is determined based upon the annual service cost of benefits (the actuarial cost of benefits earned during a period) and the interest cost on those liabilities, less the expected return on plan assets. The expected long-term rate of return on plan assets is applied to a calculated value of plan assets that recognizes changes in fair value over a five-year period. This practice is intended to reduce year-to-year volatility in pension expense, but it can have the effect of delaying recognition of differences between actual returns on assets and expected returns based on long-term rate of return assumptions. Amortization of unrecognized net gain or loss resulting from actual experience different from that assumed and from changes in assumptions (excluding asset gains and losses not yet reflected in market-related value) is included as a component of net periodic benefit cost for a year. If, as of the beginning of the year, the unrecognized net gain or loss exceeds 10 percent of the greater of the projected benefit obligation and the market-related value of plan assets, then the amortization is the excess divided by the average remaining service period of participating employees expected to receive benefits under the plan.
	Pre-tax amounts not yet recognized in net periodic pension costs, but rather recognized in accumulated other comprehensive loss as of December 31, 2013 and 2012, consist of:
		As of December 31,
		2013				2012
		(in thousands)
	Unrecognized actuarial losses	$	8,439			$	12,427
	Unrecognized prior service costs	136				153
	Unrecognized transition obligation	—				—
	Accumulated other comprehensive loss	$	8,575			$	12,580
	The estimated net loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year is $436,000.
	Pre-tax changes recognized in other comprehensive income (loss) during 2013, 2012, and 2011, were as follows:
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Net actuarial gain (loss)	$	2,766			$	(4,680	)		$	(3,014	)
	Prior service cost	—				—				(170		)
	Less: Amortization of:
	Prior service cost	(17		)		(17		)		—
	Actuarial loss	(1,222		)		(754		)		(405		)
	Total other comprehensive income (loss)	$	4,005			$	(3,909	)		$	(2,779	)
	Components of Net Periodic Benefit Cost for Both Pension Plans
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Components of net periodic benefit cost:
	Service cost	$	6,291			$	4,934			$	3,800
	Interest cost	1,627				1,374				1,184
	Expected return on plan assets that reduces periodic pension cost	(1,538		)		(1,165		)		(880		)
	Amortization of prior service cost	17				17				—
	Amortization of net actuarial loss	1,222				754				405
	Net periodic benefit cost	$	7,619			$	5,914			$	4,509
	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.
Pension Plan Assumptions
Weighted-average assumptions to measure the Company’s projected benefit obligation and net periodic benefit cost are as follows:
	As of December 31,
	2013		2012		2011
Projected benefit obligation
Discount rate	5.00%		3.90%		4.70%
Rate of compensation increase	6.20%		6.20%		6.20%
Net periodic benefit cost
Discount rate	3.90%		4.70%		5.30%
Expected return on plan assets	7.50%		7.50%		7.50%
Rate of compensation increase	6.20%		6.20%		6.20%
The Company’s pension investment policy includes various guidelines and procedures designed to ensure that assets are prudently invested in a manner necessary to meet the future benefit obligation of the Pension Plans. The policy does not permit the direct investment of plan assets in the Company’s securities. The Qualified Pension Plan's investment horizon is long-term and accordingly the target asset allocations encompass a strategic, long-term perspective of capital markets, expected risk and return behavior and perceived future economic conditions. The key investment principles of diversification, assessment of risk, and targeting the optimal expected returns for given levels of risk are applied.
The Qualified Pension Plan's investment portfolio contains a diversified blend of investments, which may reflect varying rates of return. The investments are further diversified within each asset classification. This portfolio diversification provides protection against a single security or class of securities having a disproportionate impact on aggregate investment performance. The actual asset allocations are reviewed and rebalanced on a periodic basis to maintain the target allocations. The weighted-average asset allocation of the Qualified Pension Plan is as follows:
	Target			As of December 31,
Asset Category	2014			2013			2012
Equity securities	44	%		43.6	%		42.7	%
Debt securities	33	%		32.2	%		32.8	%
Other	23	%		24.2	%		24.5	%
Total	100	%		100	%		100	%
There is no asset allocation of the Nonqualified Pension Plan since there are no plan assets in that plan. An expected return on plan assets of 7.5 percent was used to calculate the Company’s obligation under the Qualified Pension Plan for 2013 and 2012. Factors considered in determining the expected rate of return include the long-term historical rate of return provided by the equity and debt securities markets and input from the investment consultants and trustees managing the plan assets. The difference in investment income using the projected rate of return compared to the actual rates of return for the past two years was not material and is not expected to have a material effect on the accompanying statements of operations or cash flows from operating activities in future years.
Fair Value Assumptions
The fair value of the Company’s Qualified Pension Plan assets as of December 31, 2013, utilizing the fair value hierarchy discussed in Note 11 – Fair Value Measurements is as follows:
								Fair Value Measurements Using:
	Actual Asset Allocation			Total				Level 1 Inputs				Level 2 Inputs		Level 3 Inputs
				(in thousands)
Cash	—	%		$	—			$	—			$	—	$	—
Equity Securities
Domestic (1)	29.9	%		7,371				4,888				2,483		—
International (2)	13.7	%		3,373				3,373				—		—
Total Equity Securities	43.6	%		10,744				8,261				2,483		—
Fixed Income Securities
High-Yield Bonds (3)	5.9	%		1,448				1,448				—		—
Core Fixed Income (4)	20.3	%		5,006				5,006				—		—
Floating Rate Corp Loans (5)	6	%		1,483				1,483				—		—
Total Fixed Income Securities	32.2	%		7,937				7,937				—		—
Other Securities:
Commodities (6)	3.8	%		945				945				—		—
Real Estate (7)	3.5	%		859				—				—		859
Hedge Fund (8)	14.3	%		3,517				955				—		2,562
Collective Investment Trusts (9)	2.6	%		656				—				656		—
Total Other Securities	24.2	%		5,977				1,900				656		3,421
Total Investments	100	%		$	24,658			$	18,098			$	3,139	$	3,421
-1	Level 1 equity securities consist of United States large and small capitalization companies, which are actively traded securities that can be sold upon demand. Level 2 equity securities are investments in a collective investment fund that is valued at net asset value based on the value of the underlying investments and total units outstanding on a daily basis. The objective of this fund is to approximate the S&P 500 by investing in one or more collective investment funds.
-2	International equity securities consists of a well-diversified portfolio of holdings of mostly large issuers organized in developed countries with liquid markets, commingled with investments in equity securities of issuers located in emerging markets and believed to have strong sustainable financial productivity at attractive valuations.
-3	High-yield bonds consist of non-investment grade fixed income securities. The investment objective is to obtain high current income. Due to the increased level of default risk, security selection focuses on credit-risk analysis.
-4	The objective is to achieve value added from sector or issue selection by constructing a portfolio to approximate the investment results of the Barclay's Capital Aggregate Bond Index with a modest amount of variability in duration around the index.
-5	Investments consist of floating rate bank loans. The interest rates on these loans are typically reset on a periodic basis to account for changes in the level of interest rates.
-6	Investments with exposure to commodity price movements, primarily through the use of futures, swaps and other commodity-linked securities.
-7	The investment objective of direct real estate is to provide current income with the potential for long-term capital appreciation. Ownership in real estate entails a long-term time horizon, periodic valuations, and potentially low liquidity.
-8	The hedge fund portfolio includes an investment in an actively traded global mutual fund that focuses on alternative investments and a hedge fund of funds that invests both long and short using a variety of investment strategies.
-9	Collective investment trusts invest in short-term investments and are valued at the net asset value of the collective investment trust. The net asset value, as provided by the trustee, is used as a practical expedient to estimate fair value. The net asset value is based on the fair value of the underlying investments held by the fund less its liabilities.
Included below is a summary of the changes in Level 3 plan assets (in thousands):
31-Dec-12	$	2,384
Purchases	742
Realized gain on assets	161
Unrealized gain on assets	134
31-Dec-13	$	3,421
The fair value of the Company’s pension plan assets as of December 31, 2012, is as follows:
								Fair Value Measurements Using:
	Actual Asset Allocation			Total				Level 1 Inputs				Level 2 Inputs		Level 3 Inputs
				(in thousands)
Cash and Money Market Funds	3.8	%		$	778			$	778			$	—	$	—
Equity Securities
Domestic (1)	29.2	%		5,920				5,920				—		—
International (2)	13.5	%		2,740				2,740				—		—
Total Equity Securities	42.7	%		8,660				8,660				—		—
Fixed Income Securities
High-Yield Bonds (3)	6.1	%		1,240				1,240				—		—
Core Fixed Income (4)	20.8	%		4,204				4,204				—		—
Floating Rate Corp Loans (5)	5.9	%		1,186				1,186				—		—
Total Fixed Income Securities	32.8	%		6,630				6,630				—		—
Other Securities:
Commodities (6)	3.3	%		669				669				—		—
Real Estate (7)	3.9	%		783				—				—		783
Hedge Fund (8)	13.5	%		2,734				1,133				—		1,601
Total Other Securities	20.7	%		4,186				1,802				—		2,384
Total Investments	100	%		$	20,254			$	17,870			$	—	$	2,384
-1	Equity securities of United States large and small capitalization companies, which are actively traded securities that can be sold upon demand.
-2	International equity securities consists of a well-diversified portfolio of holdings of mostly large issuers organized in developed countries with liquid markets, commingled with investments in equity securities of issuers located in emerging markets and believed to have strong sustainable financial productivity at attractive valuations.
-3	High-yield bonds consist of non-investment grade fixed income securities. The investment objective is to obtain high current income. Due to the increased level of default risk, security selection focuses on credit-risk analysis.
-4	The objective is to achieve value added from sector or issue selection by constructing a portfolio to approximate the investment results of the Barclay's Capital Aggregate Bond Index with a modest amount of variability in duration around the index.
-5	Investments consist of floating rate bank loans. The interest rates on these loans are typically reset on a periodic basis to account for changes in the level of interest rates.
-6	Investments with exposure to commodity price movements, primarily through the use of futures, swaps and other commodity-linked securities.
-7	The investment objective of direct real estate is to provide current income with the potential for long-term capital appreciation. Ownership in real estate entails a long-term time horizon, periodic valuations, and potentially low liquidity.
-8	The hedge fund portfolio includes an investment in an actively traded global mutual fund that focuses on alternative investments and a hedge fund of funds that invests both long and short using a variety of investment strategies.
Included below is a summary of the changes in Level 3 plan assets (in thousands):
31-Dec-11	$	—
Purchases	2,329
Investment Returns	55
31-Dec-12	$	2,384
Contributions
The Company contributed $5.0 million, $5.4 million, and $5.3 million, to the Pension Plans in the years ended December 31, 2013, 2012, and 2011, respectively. The Company is expected to make a $4.3 million contribution to the Pension Plans in 2014.
Benefit Payments
The Pension Plans made actual benefit payments of $3.3 million, $1.0 million, and $1.5 million in the years ended December 31, 2013, 2012, and 2011, respectively. Expected benefit payments over the next 10 years are as follows:
Years Ending December 31,		(in thousands)
2014		$	2,120
2015		$	2,837
2016		$	3,287
2017		$	3,993
2018		$	4,407
2019 through 2023		$	33,031

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Asset Retirement Obligations	'
	Note 9 – Asset Retirement Obligations
	The Company recognizes an estimated liability for future costs associated with the abandonment of its oil and gas properties. A liability for the fair value of an asset retirement obligation and a corresponding increase to the carrying value of the related long-lived asset are recorded at the time a well is completed or acquired. The increase in carrying value is included in proved oil and gas properties in the accompanying balance sheets. The Company depletes the amount added to proved oil and gas property costs and recognizes expense in connection with the accretion of the discounted liability over the remaining estimated economic lives of the respective oil and gas properties. Cash paid to settle asset retirement obligations is included in the operating section of the Company’s accompanying statements of cash flows.
	The Company’s estimated asset retirement obligation liability is based on historical experience in abandoning wells, estimated economic lives, estimates as to the cost to abandon the wells in the future, and federal and state regulatory requirements. The liability is discounted using the credit-adjusted risk-free rate estimated at the time the liability is incurred or revised. The credit-adjusted risk-free rates used to discount the Company’s abandonment liabilities range from 5.5 percent to 12 percent. Revisions to the liability could occur due to changes in estimated abandonment costs or well economic lives or if federal or state regulators enact new requirements regarding the abandonment of wells.
	A reconciliation of the Company’s asset retirement obligation liability is as follows:
		As of December 31,
		2013			2012
		(in thousands)
	Beginning asset retirement obligation	$	120,518		$	95,906
	Liabilities incurred	18,682			13,050
	Liabilities settled	(33,129		)	(8,101		)
	Accretion expense	5,997			4,679
	Revision to estimated cash flows	9,118			14,984
	Ending asset retirement obligation	$	121,186		$	120,518
	As of December 31, 2013 and 2012, the Company had $3.0 million and $1.4 million, respectively, of asset retirement obligation associated with the oil and gas properties held for sale included in a separate line item on the Company’s accompanying balance sheets. Additionally, as of December 31, 2013 and 2012, accounts payable and accrued expenses contain $2.5 million and $6.2 million, respectively, related to the Company’s current asset retirement obligation liability for estimated plugging and abandonment costs associated with platforms that are being relinquished or retired.

Derivative_Financial_Instrumen

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2013
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 the exposure to potentially adverse market changes in commodity prices and the associated impact on cash flows. The Company’s derivative contracts in place include swap and collar arrangements for oil, gas, and NGLs.
	As of December 31, 2013, the Company has commodity derivative contracts outstanding through the second quarter of 2018 for a total of 18.8 million Bbls of oil production, 265.9 million MMBtu of gas production, and 2.5 million Bbls of NGL production. As of February 12, 2014, the Company had commodity derivative contracts in place through the second quarter of 2018 for a total of 17.5 million Bbls of oil, 237.9 million MMBtu of gas, and 4.0 million Bbls of NGLs. These volumes are net of scheduled January 2014 settlements, as well as the early settlement of 18.0 million MMBtu of gas swaps and collars in January 2014 due to the divestiture of assets in our Mid-Continent region at the end of 2013.
	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 December 31, 2013:
	Oil Contracts
	Oil Swaps
	Contract Period		Volumes			Weighted-
						Average
						Contract
						Price
			(Bbls)			(per Bbl)
	First quarter 2014		2,600,000			$	96.92
	Second quarter 2014		2,373,000			$	94.95
	Third quarter 2014		973,000			$	95.25
	Fourth quarter 2014		891,000			$	95.16
	2015		2,911,000			$	89.06
	2016		2,704,000			$	85.19
	All oil swaps*		12,452,000
	*Oil swaps are comprised of NYMEX WTI (97%) and Argus LLS (3%).
	Oil Collars
	Contract Period		NYMEX WTI			Weighted-				Weighted-
			Volumes			Average				Average
						Floor				Ceiling
						Price				Price
			(Bbls)			(per Bbl)				(per Bbl)
	First quarter 2014		694,000			$	80.97			$	115.07
	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		6,387,000
	Natural Gas Contracts
	Gas Swaps
	Contract Period		Volumes			Weighted-
						Average
						Contract
						Price
			(MMBtu)			(per MMBtu)
	First quarter 2014		33,651,000			$	4.25
	Second quarter 2014		25,729,000			$	3.96
	Third quarter 2014		26,398,000			$	4.01
	Fourth quarter 2014		23,965,000			$	4.01
	2015		63,317,000			$	4.03
	2016		39,014,000			$	4.18
	2017		23,430,000			$	4.21
	2018		10,200,000			$	4.31
	All gas swaps*		245,704,000
	*Natural gas swaps are comprised of IF El Paso Permian (3%), IF HSC (77%), IF NGPL TXOK (3%), IF NNG Ventura (2%), IF PEPL (6%), IF Reliant N/S (8%), and IF NGPL MidCon (1%).
	Gas Collars
	Contract Period		Volumes			Weighted-				Weighted-
						Average				Average
						Floor				Ceiling
						Price				Price
			(MMBtu)			(per MMBtu)				(per MMBtu)
	First quarter 2014		1,540,000			$	4.39			$	5.58
	Second quarter 2014		4,194,000			$	4.38			$	5.29
	2015		14,480,000			$	3.96			$	4.3
	All gas collars*		20,214,000
	*Natural gas collars are comprised of IF El Paso Permian (2%), IF HSC (57%), IF NGPL TXOK (3%), IF NNG Ventura (5%), IF PEPL (7%), IF Reliant N/S (14%), and IF TETCO STX (12%).
	NGL Contracts
	NGL Swaps
Contract Period		Volumes			Weighted-
					Average
					Contract
					Price
		(Bbls)			(per Bbl)
First quarter 2014		913,000			$	59.72
Second quarter 2014		565,000			$	63.22
Third quarter 2014		544,000			$	62.34
Fourth quarter 2014		527,000			$	61.57
All NGL swaps*		2,549,000
*NGL swaps are comprised of OPIS IsoButane Mt Belv Non TET (2%), OPIS Natural Gasoline Mt Belv Non TET (34%), OPIS NButane Mt Belv Non TET (3%), and OPIS Propane Mt Belv TET (61%).
Commodity Derivative Contracts Entered into After December 31, 2013
The following tables summarize all commodity derivative contracts entered between January 1, 2014 and February 12, 2014:
Gas Contracts
Gas Swaps
Contract Period		Volumes			Weighted-
					Average
					Contract
					Price
		(MMBtu)			(per MMBtu)
First quarter 2014		261,000			$	4.39
Second quarter 2014		365,000			$	3.84
Third quarter 2014		341,000			$	3.89
Fourth quarter 2014		321,000			$	3.97
2015		1,133,000			$	3.72
2016		69,000			$	4.12
All gas swaps*		2,490,000
*Natural gas swaps are comprised of IF NNG Ventura (30%) and IF CIG N System (70%).
NGL Contracts
NGL Swaps
Contract Period		Volumes			Weighted-
					Average
					Contract
					Price
		(Bbls)			(per Bbl)
First quarter 2014		516,000			$	54.85
Second quarter 2014		531,000			$	52.53
Third quarter 2014		416,000			$	52.47
Fourth quarter 2014		334,000			$	52.52
All NGL swaps*		1,797,000
*NGL swaps are comprised of OPIS Natural Gasoline Mt Belv Non TET (17%) and OPIS Propane Mt Belv TET (83%).
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 asset of $21.5 million and $38.7 million at December 31, 2013 and 2012, respectively.
The following tables detail the fair value of derivatives recorded in the accompanying balance sheets, by category:
	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
	As of December 31, 2012
	Derivative Assets						Derivative Liabilities
	Balance Sheet		Fair Value				Balance Sheet		Fair Value
	Classification						Classification
	(in thousands)
Commodity Contracts	Current assets		$	37,873			Current liabilities		$	8,999
Commodity Contracts	Noncurrent assets		16,466				Noncurrent liabilities		6,645
Derivatives not designated as hedging instruments			$	54,339					$	15,644
Offsetting of Derivative Assets and Liabilities
As of December 31, 2013 and 2012, 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 transactions 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 December 31,								As of December 31,
Offsetting of Derivative Assets and Liabilities		2013				2012				2013				2012
		(in thousands)
Gross amounts presented in the accompanying balance sheets		$	52,510			$	54,339			$	(31,020	)		$	(15,644	)
Amounts not offset in the accompanying balance sheets		(30,652		)		(13,400		)		30,652				13,400
Net amounts		$	21,858			$	40,939			$	(368	)		$	(2,244	)
Discontinuance of Cash Flow Hedge Accounting
Prior to January 1, 2011, the Company designated its commodity derivative contracts as cash flow hedges, for which unrealized changes in fair value were recorded to AOCIL, to the extent the hedges were effective.  As of January 1, 2011, the Company elected to de-designate all of its commodity derivative contracts that had been previously designated as cash flow hedges at December 31, 2010. As a result, subsequent to December 31, 2010, the Company recognizes all gains and losses from changes in commodity derivative fair values immediately in earnings rather than deferring any such amounts in AOCIL. The Company had no derivatives designated as cash flow hedges for the years ended December 31, 2013, and 2012.
As a result of discontinuing hedge accounting on January 1, 2011, fair values at December 31, 2010, were frozen in AOCIL as of the de-designation date and were reclassified into earnings as the original derivative transactions settled.  As of December 31, 2013, all commodity derivative contracts that had been previously designated as cash flow hedges have settled and have been reclassified into earnings from AOCIL. Please refer to Note 11 - Fair Value Measurements for more information regarding the Company’s derivative instruments, including its valuation techniques.
The following table summarizes the components of derivative (gain) loss presented in the accompanying statements of operations:
	For the Years Ended December 31,
	2013				2012				2011
	(in thousands)
Derivative cash settlement (gain) loss:
Oil contracts	$	15,161			$	11,893			$	22,633
Gas contracts	(30,338		)		(47,270		)		(10,711		)
NGL contracts	(6,885		)		(8,887		)		13,749
Total derivative cash settlement (gain) loss (1)	(22,062		)		(44,264		)		25,671
Derivative (gain) loss:
Oil contracts	(496		)		(31,981		)		(3,391		)
Gas contracts	16,285				31,777				(64,310		)
NGL contracts	3,193				(11,162		)		4,944
Total derivative gain (2)	$	(3,080	)		$	(55,630	)		$	(37,086	)
(1)	Total derivative cash settlement gain (loss) is reported in the derivative cash settlement gain (loss) line item on the consolidated statements of cash flows within net cash provided by operating activities.
(2)	Total derivative gain is reported in the derivative gain line item on the consolidated statements of cash flows within net cash provided by operating activities.
The following table details the effect of derivative instruments on AOCIL and the accompanying statements of operations (net of income tax):
			Location on		For the Years Ended December 31,
			Accompanying
			Statements of
	Derivatives		Operations		2013				2012				2011
					(in thousands)
Amount reclassified from AOCIL	Commodity Contracts		Realized hedge gain (loss)		$	1,115			$	(2,264	)		$	12,997
The realized net hedge loss for the year ended December 31, 2013, net hedge gain for the year ended December 31, 2012, and net hedge loss for the year ended December 31, 2011, shown net of income tax in the table above, are comprised of realized cash settlements on commodity derivative contracts that were previously designated as cash flow hedges. Realized hedge gains or losses from the settlement of commodity derivatives previously designated as cash flow hedges are reported in the total operating revenues and other income section of the accompanying statements of operations.  The Company realized a pre-tax net loss of $1.8 million, a pre-tax net gain of $3.9 million, and a pre-tax net loss of $20.7 million from its commodity derivative contracts for the years ended December 31, 2013, 2012, and 2011, respectively.
As noted above, effective January 1, 2011, the Company elected to de-designate all of its commodity derivative contracts that had been previously designated as cash flow hedges. No new gains or losses are deferred in AOCIL at December 31, 2013, and 2012, respectively.
Credit Related Contingent Features
As of December 31, 2013, and through the filing date of this report, all of the Company’s derivative counterparties were members of the Company’s credit facility syndicate. The Company’s obligations under its credit facility and derivative contracts are secured by liens on substantially all of the Company’s proved oil and gas properties.
Convertible Note Derivative Instrument
The contingent interest provision of the 3.50% Senior Convertible Notes was an embedded derivative instrument. The 3.50% Senior Convertible Notes were settled during the second quarter of 2012. Please refer to Note 5 - Long-term Debt for additional discussion.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Disclosures [Text Block]	'
	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 table is a listing of the Company’s assets and liabilities that are measured at fair value and where they were classified 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 that is measured at fair value on a nonrecurring basis.
	The following table is a listing of the Company’s assets and liabilities that are measured at fair value and where they were classified within the hierarchy as of December 31, 2012:
		Level 1			Level 2			Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	54,339		$	—
	Proved oil and gas properties (2)	$	—		$	—		$	209,959
	Unproved oil and gas properties (2)	$	—		$	—		$	42,765
	Liabilities:
	Derivatives (1)	$	—		$	15,644		$	—
	Net Profits Plan (1)	$	—		$	—		$	78,827
	(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 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 forward commodity price curves, 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. The considered 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. Currently, one counterparty posts collateral when requested by the Company. 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 derivative liability position. 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 and takes 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 bank syndicate.
	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 accounting authoritative 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 valuation technique, 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, which 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 December 31, 2013, would differ by approximately $5 million. A one percent increase in the discount rate would decrease the liability by approximately $2 million, whereas a one percent decrease in the discount rate would increase the liability by approximately $2 million. Actual cash payments to be made to participants in future periods are dependent on realized actual production, realized commodity prices, and actual 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 of 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 Years Ended December 31,
		2013			2012			2011
		(in thousands)
	Beginning balance	$	78,827		$	107,731		$	135,850
	Net increase (decrease) in liability (1)	3,527			(9,251		)	2,269
	Net settlements (1) (2) (3)	(25,369		)	(19,653		)	(30,388		)
	Transfers in (out) of Level 3	—			—			—
	Ending balance	$	56,985		$	78,827		$	107,731
	-1	Net changes in the 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 amounts in the table include cash payments made or accrued under the Net Profits Plan of $10.3 million, $2.3 million, and $6.3 million relating to divestiture proceeds for the years ended December 31, 2013, 2012, and 2011, respectively.
	-3	During 2011, the Company elected to cash out several Net Profits Plan pools with a $2.6 million direct payment. As a result, the Company reduced its Net Profits Plan liability by that amount.  There was no impact on the accompanying statements of operations for the period ended December 31, 2011, related to these settlements.
	Long-term Debt
	The following table reflects the fair value of the Senior Notes measured at fair value 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 December 31, 2013 or 2012, as they are recorded at historical value.
		As of December 31,
		2013			2012
		(in thousands)
	2019 Notes	$	374,290		$	371,875
	2021 Notes	$	373,625		$	371,070
	2023 Notes	$	422,000		$	424,200
2024 Notes (1)	$	475,315		$	—
(1) The 2024 Notes were issued on May 20, 2013.
The carrying value of the Company’s credit facility approximates its fair value, as the applicable interest rates are floating, based on prevailing market rates.
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 December 31, 2013, and 2012. 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 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 pricing, adjusted for basis differentials, 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.
As a result of asset write-downs, the proved oil and gas properties measured at fair value within the accompanying balance sheets totaled $62.2 million and $210.0 million as of December 31, 2013, and 2012, respectively.
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 utilizes a market approach, which 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.
As a result of asset write-downs, unproved oil and gas properties measured at fair value within the accompanying balance sheets totaled $3.3 million as of December 31, 2013 and $42.8 million at December 31, 2012.
Acquisitions of proved and unproved properties are measured at fair value as of the acquisition date using a discounted cash flow model similar to the Company’s approach in measuring the fair value of proved and unproved properties, as discussed in the paragraphs above. Due to the unobservable characteristics of the inputs, the fair value of acquired properties are considered Level 3 within the fair value hierarchy.
Materials Inventory
Materials inventory is valued at the lower of cost or market. The Company uses Level 2 inputs to measure the fair value of materials inventory, which is primarily comprised of tubular goods. The Company uses third party market quotes and compares the quotes to the book value of the materials inventory. If the book value exceeds the quoted market price, the Company reduces the book value to the market price. The considered factors result in an estimated exit-price. Management believes this approach provides a reasonable and consistent methodology for valuing materials inventory. There were no materials inventory measured at fair value within the accompanying balance sheets at December 31, 2013 and 2012.
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 measured at fair value within the accompanying balance sheets at December 31, 2013 and 2012.

Acquisition_and_Development_Ag

Acquisition and Development Agreement and Carry and Earning Agreement	12 Months Ended
	Dec. 31, 2013
Acquisition and Development Agreement and Carry and Earning Agreement [Abstract]	'
Acquisition and Development Agreement and Carry and Earning Agreement	'
	Note 12 - Acquisition and Development Agreement
	In June 2011, the Company entered into an Acquisition and Development Agreement with Mitsui. Pursuant to the Acquisition and Development Agreement, the Company agreed to transfer to Mitsui a 12.5 percent working interest in certain non-operated oil and gas assets representing approximately 39,000 net acres in Dimmit, LaSalle, Maverick, and Webb Counties, Texas. As consideration for the oil and gas interests transferred, Mitsui agreed to pay, or carry, 90 percent of certain drilling and completion costs attributable to the Company’s remaining interest in these assets until Mitsui has expended an aggregate $680.0 million on behalf of the Company. Based on the Company’s forecast of the operator’s drilling plans, the carry will be fully utilized in early 2014. The Acquisition and Development Agreement also provided for reimbursement of capital expenditures and other costs, net of revenues, paid by the Company that were attributable to the transferred interest during the period between the effective date and the closing date, which the parties agreed would be applied over the carry period to cover the Company’s remaining 10 percent of drilling and completion costs for the affected acreage.
	As of December 31, 2013, the Company held $95.0 million in cash that is contractually restricted for use in the development of assets covered by the Acquisition and Development Agreement. This cash relates to the reimbursement of net costs for the period between the effective date and closing date, as discussed above, as well as an estimate of 90 percent of two months of activity of the Company’s proportionate share of estimated drilling and completion costs. This restricted cash is classified as a noncurrent asset in the accompanying balance sheets. The Company has recorded a corresponding liability equal to the restricted cash balance. The portion of the liability related to development operations expected to occur within the next year is recorded in accounts payable and accrued expenses within the accompanying balance sheets. The portion of the liability related to development operations expected to occur more than one year in the future is recorded in other noncurrent liabilities within the accompanying balance sheets. As the remaining development operations are expected to be completed within the next year, the entire amount is recorded in accounts payable and accrued expenses within the accompanying balance sheets as of December 31, 2013. There was no net impact on the accompanying statements of cash flows as restricted cash was offset against the corresponding liability in investing activities. There is no direct impact to the accompanying statements of operations as a result of the Acquisition and Development Agreement, with the exception of legal and commission costs associated with the execution of the arrangement which were expensed in 2011. Of the original $680.0 million carry amount, $573.8 million had been spent as of December 31, 2013.

Suspended_Well_Costs

Suspended Well Costs	12 Months Ended
	Dec. 31, 2013
Suspended Well Costs [Abstract]	'
Suspended Well Costs Disclosure [Text Block]	'
	Note 13 - Suspended Well Costs
	The following table reflects the net changes in capitalized exploratory well costs during 2013, 2012, and 2011. The table does not include amounts that were capitalized and either subsequently expensed or reclassified to producing well costs in the same year:
		For the Years Ended December 31,
		2013			2012			2011
		(in thousands)
	Beginning balance on January 1,	$	9,100		$	18,600		$	35,862
	Additions to capitalized exploratory well costs pending the determination of proved reserves	34,527			9,100			15,618
	Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	(9,100		)	(5,865		)	(32,880		)
	Capitalized exploratory well costs charged to expense	—			(12,735		)	—
	Ending balance at December 31,	$	34,527		$	9,100		$	18,600
	The following table provides an aging of capitalized exploratory well costs based on the date the drilling was completed and the number of projects for which exploratory well costs have been capitalized for more than one year since the completion of drilling:
		As of December 31,
		2013			2012			2011
		(in thousands)
	Exploratory well costs capitalized for one year or less	$	34,527		$	9,100		$	15,618
	Exploratory well costs capitalized for more than one year	—			—			2,982
	Ending balance at December 31,	$	34,527		$	9,100		$	18,600
	Number of projects with exploratory well costs that have been capitalized more than a year	—			—			2
	In the third quarter of 2012, the Company expensed $3.6 million of costs related to two exploratory wells that had been disclosed at December 31, 2011, as suspended well costs being capitalized for more than one year.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Consolidation, Policy [Policy Text Block]	'
	Basis of Presentation
	The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries and have been prepared in accordance with GAAP and the instructions to Form 10-K and Regulation S-X. Subsidiaries that the Company does not control are accounted for using the equity or cost methods as appropriate. Equity method investments are included in other noncurrent assets in the accompanying consolidated balance sheets (“accompanying balance sheets”). Intercompany accounts and transactions have been eliminated. In connection with the preparation of the consolidated financial statements, the Company evaluated subsequent events after the balance sheet date of December 31, 2013, through the filing date of this report. Certain prior period amounts have been reclassified to conform to the current period presentation
Use of Estimates, Policy [Policy Text Block]	'
	Use of Estimates in the Preparation of Financial Statements
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of proved oil and gas reserves, assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Estimates of proved oil and gas reserve quantities provide the basis for the calculation of depletion, depreciation, and amortization expense, impairment of proved properties, asset retirement obligations, and the Net Profits Interest Bonus Plan (“Net Profits Plan”) liability, each of which represents a significant component of the accompanying consolidated financial statements.
Cash and Cash Equivalents, Policy [Policy Text Block]	'
	Cash and Cash Equivalents
	The Company considers all liquid investments purchased with an initial maturity of three months or less to be cash equivalents. The carrying value of cash and cash equivalents approximates fair value due to the short-term nature of these instruments.
Restricted cash [Policy Text Block]	'
	Restricted Cash
	The Company’s restricted cash balance mainly consists of cash payments that are contractually restricted to be used solely for development of long-term capital assets pursuant to the Company’s Acquisition and Development Agreement with Mitsui and accordingly are classified as non-current assets. Please refer to Note 12 - Acquisition and Development Agreement for additional information.
Receivables, Policy [Policy Text Block]	'
	Accounts Receivable
	The Company’s accounts receivable consist mainly of receivables from oil, gas, and NGL purchasers and from joint interest owners on properties the Company operates. For receivables from joint interest owners, the Company typically has the ability to withhold future revenue disbursements to recover non-payment of joint interest billings. Generally, the Company’s oil and gas receivables are collected within two months, and the Company has had minimal bad debts.
	Although diversified among many companies, collectability is dependent upon the financial wherewithal of each individual company and is influenced by the general economic conditions of the industry. Receivables are not collateralized. As of December 31, 2013 and 2012, the Company had no allowance for doubtful accounts recorded.
Full Cost or Successful Efforts, Policy [Policy Text Block]	'
	Oil and Gas Producing Activities
	The Company accounts for its oil and gas exploration and development costs using the successful efforts method. Geological and geophysical costs are expensed as incurred. Exploratory well costs are capitalized pending further evaluation of whether economically recoverable reserves have been found. If economically recoverable reserves are not found, exploratory well costs are expensed as dry holes. The application of the successful efforts method of accounting requires management’s judgment to determine the proper designation of wells as either development or exploratory, which will ultimately determine the proper accounting treatment of costs of dry holes. Once a well is drilled, the determination that economic proved reserves have been discovered may take considerable time and judgment. Exploratory dry hole costs are included in cash flows from investing activities as part of capital expenditures within the accompanying statements of cash flows. The costs of development wells are capitalized whether those wells are successful or unsuccessful.
	DD&A of capitalized costs related to proved oil and gas properties is calculated on a pool-by-pool basis using the units-of-production method based upon proved reserves. The computation of DD&A takes into consideration restoration, dismantlement, and abandonment costs as well as the anticipated proceeds from salvaging equipment. As of December 31, 2013, and 2012, the estimated salvage value of the Company's equipment was $57.5 million and $64.4 million, respectively.
Net Profits Plan [Policy Text Block]	'
	Net Profits Plan
	The Company records the estimated fair value of expected future payments made under the Net Profits Plan as a noncurrent liability in the accompanying balance sheets. The underlying assumptions used in the calculation of the estimated liability include estimates of production, proved reserves, recurring and workover lease operating expense, transportation, production and ad valorem tax rates, present value discount factors, pricing assumptions, and overall market conditions. The estimates used in calculating the long-term liability are adjusted from period-to-period based on the most current information attributable to the underlying assumptions. Changes in the estimated liability of future payments associated with the Net Profits Plan are recorded as increases or decreases to expense in the current period as a separate line item in the accompanying consolidated statements of operations (“accompanying statements of operations”), as these changes are considered changes in estimates.
	The distribution amounts due to participants and payable in each period under the Net Profits Plan as cash compensation related to periodic operations are recognized as compensation expense and are included within general and administrative expense and exploration expense in the accompanying statements of operations. The corresponding current liability is included in accounts payable and accrued expenses in the accompanying balance sheets. This treatment provides for a consistent matching of cash expense with net cash flows from the oil and gas properties in each respective pool of the Net Profits Plan. For additional discussion, please refer to the heading Net Profits Plan in Note 7 – Compensation Plans and Note 11 – Fair Value Measurements.
Asset Retirement Obligations, Policy [Policy Text Block]	'
	Asset Retirement Obligations
	The Company recognizes an estimated liability for future costs associated with the abandonment of its oil and gas properties. A liability for the fair value of an asset retirement obligation and corresponding increase to the carrying value of the related long-lived asset are recorded at the time a well is completed or acquired. The increase in carrying value is included in proved oil and gas properties in the accompanying balance sheets. The Company depletes the amount added to proved oil and gas property costs and recognizes expense in connection with the accretion of the discounted liability over the remaining estimated economic lives of the respective oil and gas properties. For additional discussion, please refer to Note 9 – Asset Retirement Obligations.
Revenue Recognition, Policy [Policy Text Block]	'
	Revenue Recognition
	The Company derives revenue primarily from the sale of produced oil, gas, and NGLs. Revenue is recognized when the Company’s production is delivered to the purchaser, but payment is generally received between 30 and 90 days after the date of production. No revenue is recognized unless it is determined that title to the product has transferred to the purchaser. At the end of each month, the Company estimates the amount of production delivered to the purchaser and the price the Company will receive. The Company uses knowledge of its properties and historical performance, NYMEX, OPIS, and local spot market prices, quality and transportation differentials, and other factors as the basis for these estimates.
	The Company uses the sales method of accounting for gas revenue whereby sales revenue is recognized on all gas sold to purchasers, regardless of whether the sales are proportionate to the Company’s ownership in the property. An asset or liability is recognized to the extent that there is an imbalance in excess of the remaining gas reserves on the underlying properties.
Property, Plant and Equipment, Impairment [Policy Text Block]	'
	Impairment of Proved and Unproved Properties
	Proved oil and gas property costs are evaluated for impairment and reduced to fair value, which is based on expected future discounted cash flows, when there is an indication that the carrying costs may not be recoverable. Expected future cash flows are calculated on all developed proved reserves and risk adjusted proved undeveloped, probable, and possible reserves using a discount rate and price forecasts that management believes are representative of current market conditions. The prices for oil and gas are forecasted based on 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 pricing, adjusted for basis differentials, 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. An impairment is recorded on unproved property when the Company determines that either the property will not be developed or the carrying value is not realizable.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	'
	Stock-Based Compensation
	At December 31, 2013, the Company had stock-based employee compensation plans that included RSUs, PSUs, restricted stock awards, and stock options issued to employees and non-employee directors, as more fully described in Note 7 - Compensation Plans. The Company records expense associated with the fair value of stock-based compensation in accordance with authoritative accounting guidance, which is based on the estimated fair value of these awards determined at the time of grant
Income Tax, Policy [Policy Text Block]	'
	Income Taxes
	The Company accounts for deferred income taxes whereby deferred tax assets and liabilities are recognized based on the tax effects of temporary differences between the carrying amounts on the financial statements and the tax basis of assets and liabilities, as measured using current enacted tax rates. These differences will result in taxable income or deductions in future years when the reported amounts of the assets or liabilities are recorded or settled, respectively. The Company records deferred tax assets and associated valuation allowances, when appropriate, to reflect amounts more likely than not to be realized based upon Company analysis.
Earnings Per Share, Policy [Policy Text Block]	'
	Earnings per Share
	Basic net income (loss) per common share is calculated by dividing net income or loss available to common stockholders by the basic weighted-average common shares outstanding for the respective period. The earnings per share calculations reflect the impact of any repurchases of shares of common stock made by the Company.
	Diluted net income (loss) per common share is calculated by dividing adjusted net income or loss 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, contingent PSUs, and shares into which the 3.50% Senior Convertible Notes were convertible. When there is a loss from continuing operations, as was the case for the year ended December 31, 2012, all potentially dilutive shares are anti-dilutive and are consequently excluded from the calculation of diluted earnings per share.
	PSUs represent the right to receive, upon settlement of the PSUs after the completion of the three-year performance period, a number of shares of the Company’s common stock that may range from zero to two times 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, which 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 Share Units Under the Equity Incentive Compensation Plan.
Segment Reporting, Policy [Policy Text Block]	'
	Industry Segment and Geographic Information
	The Company operates exclusively in the exploration and production segment of the oil and gas industry and all of the Company’s operations are conducted entirely within the United States. The Company reports as a single industry segment. The Company’s gas marketing function provides mostly internal services and acts as the first purchaser of natural gas and natural gas liquids produced by the Company in certain cases. The Company considers its marketing function as ancillary to its oil and gas producing activities. The amount of income these operations generate from marketing gas produced by third parties is not material to the Company’s results of operations, and segmentation of such activity would not provide a better understanding of the Company’s performance. However, gross revenue and expense related to marketing activities for gas produced by third parties are presented in the marketed gas system revenue and marketed gas system expense line items in the accompanying statements of operations.
Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block]	'
	Off-Balance Sheet Arrangements
	The Company has not participated in transactions that generate relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance or special purpose entities (“SPEs”), which would have been established for the purpose of facilitating off-balance sheet arrangements or other contractually narrow or limited purposes. The Company has not been involved in any unconsolidated SPE transactions.
	The Company evaluates its transactions to determine if any variable interest entities exist. If it is determined that SM Energy is the primary beneficiary of a variable interest entity, that entity is consolidated into SM Energy. As of December 31, 2013, all variable interest entities have been consolidated.
Pension Benefits Policy	'
	The Company recognizes the funded status, (i.e. the difference between the fair value of plan assets and the projected benefit obligation) of the Company’s Pension Plans in the accompanying balance sheets as either an asset or a liability and recognizes a corresponding adjustment to accumulated other comprehensive income, net of tax. The projected benefit obligation is the actuarial present value of the benefits earned to date by plan participants based on employee service and compensation including the effect of assumed future salary increases. The accumulated benefit obligation uses the same factors as the projected benefit obligation but excludes the effects of assumed future salary increases. The Company’s measurement date for plan assets and obligations is December 31.
Fair Value Measurement Policy Surrounding Derivatives	'
	The Company’s commodity derivatives are measured at fair value and are included in the accompanying balance sheets as derivative assets and liabilities.
Fair Value of Financial Instruments, Policy [Policy Text Block]	'
	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 forward commodity price curves, 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. The considered 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.

Pension_Benefits_Pension_and_O

Pension Benefits Pension and Other Post-retirement Plans (Policies)	12 Months Ended
	Dec. 31, 2013
Pension and Other Post-Retirement Accounting Policies [Abstract]	'
Pension Benefits Policy	'
	The Company recognizes the funded status, (i.e. the difference between the fair value of plan assets and the projected benefit obligation) of the Company’s Pension Plans in the accompanying balance sheets as either an asset or a liability and recognizes a corresponding adjustment to accumulated other comprehensive income, net of tax. The projected benefit obligation is the actuarial present value of the benefits earned to date by plan participants based on employee service and compensation including the effect of assumed future salary increases. The accumulated benefit obligation uses the same factors as the projected benefit obligation but excludes the effects of assumed future salary increases. The Company’s measurement date for plan assets and obligations is December 31.

Derivative_Financial_Instrumen1

Derivative Financial Instruments Derivatives Policy (Policies)	12 Months Ended
	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Fair Value Measurement Policy Surrounding Derivatives	'
	The Company’s commodity derivatives are measured at fair value and are included in the accompanying balance sheets as derivative assets and liabilities.

Fair_Value_Measurements_Fair_V

Fair Value Measurements Fair Value of Financial Instruments (Policies)	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments, Policy [Policy Text Block]	'
	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 forward commodity price curves, 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. The considered 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.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Dilutive and Anti-Dilutive Shares for Earnings per Share [Table Text Block]	'
	The following table details the weighted-average dilutive and anti-dilutive securities related to stock options, RSUs, PSUs, and the 3.50% Senior Convertible Notes for the years presented:
		For the Years Ended December 31,
		2013			2012			2011
		(in thousands)
	Dilutive	1,383			—			3,809
	Anti-dilutive	—			2,102			—
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	'
	The following table sets forth the calculations of basic and diluted earnings per share:
		For the Years Ended December 31,
		2013				2012			2011
		(in thousands, except per share amounts)
	Net income (loss)	$	170,935			$	(54,249	)	$	215,416
	Basic weighted-average common shares outstanding	66,615				65,138			63,755
	Add: dilutive effect of stock options, unvested RSUs, and contingent PSUs	1,383				—			2,592
	Add: dilutive effect of 3.50% Senior Convertible Notes	—				—			1,217
	Diluted weighted-average common shares outstanding	67,998				65,138			67,564
	Basic net income (loss) per common share	$	2.57			$	(0.83	)	$	3.38
	Diluted net income (loss) per common share	$	2.51			$	(0.83	)	$	3.19
Schedule of Comprehensive Income (Loss) [Table Text Block]	'
	The changes in the balances of components comprising other comprehensive income (loss) are presented in the following table:
		Derivative Reclassification to Earnings				Pension Liability Adjustments
		(in thousands)
	For the year ended December 31, 2011
	Before tax income (loss)	$	20,707			$	(2,779	)
	Tax benefit (expense)	(7,710		)		984
	Income (loss), net of tax	$	12,997			$	(1,795	)
	For the year ended December 31, 2012
	Before tax loss	$	(3,865	)		$	(3,909	)
	Tax benefit	1,601				1,439
	Loss, net of tax	$	(2,264	)		$	(2,470	)
	For the year ended December 31, 2013
	Before tax income	$	1,777			$	4,005
	Tax expense	(662		)		(1,522		)
	Income, net of tax	$	1,115			$	2,483

Accounts_Receivable_and_Accoun1

Accounts Receivable and Accounts Payable and Accrued Expenses Accounts Receivable and Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2013
Accounts Receivable and Accounts Payable and Accrued Expenses [Abstract]	'
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]	'
	Accounts receivable are comprised of the following:
		As of December 31,
		2013		2012
		(in thousands)
	Accrued oil, gas, and NGL production revenue	$	228,169	$	160,568
	Amounts due from joint interest owners	37,517		42,740
	Acquisition and Development Agreement receivable	—		19,931
	State severance tax refunds	29,213		17,237
	Other	23,472		14,329
	Total accounts receivable	$	318,371	$	254,805
Schedule of Accounts Payable and Accrued Liabilities [Table Text Block]	'
	Accounts payable and accrued expenses are comprised of the following:
		As of December 31,
		2013		2012
		(in thousands)
	Accrued capital expenditures	$	217,820	$	243,611
	Revenue and severance tax payable	87,852		65,494
	Accrued lease operating expense	29,296		28,037
	Accrued property taxes	10,401		9,478
	Joint owner advances	96,636		69,639
	Accrued compensation	71,466		35,607
	Accrued interest	40,027		25,027
	Other	53,253		48,734
	Total accounts payable and accrued expenses	$	606,751	$	525,627

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Schedule of componenets of provision for income taxes	'
	The provision for income taxes consists of the following:
			For the Years Ended December 31,
			2013				2012				2011
			(in thousands)
	Current portion of income tax expense (benefit)
	Federal		$	—			$	—			$	(1,757	)
	State		2,121				370				1,553
	Deferred portion of income tax expense (benefit)		105,555				(29,638		)		123,789
	Total income tax expense (benefit)		$	107,676			$	(29,268	)		$	123,585
	Effective tax rate		38.6		%		35		%		36.5		%
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	'
	The components of the net deferred income tax liabilities are as follows:
			As of December 31,
			2013				2012
			(in thousands)
	Deferred tax liabilities:
	Oil and gas properties		$	768,463			$	678,624
	Derivative asset		9,529				15,942
	Other		1,245				6,443
	Total deferred tax liabilities		779,237				701,009
	Deferred tax assets:
	Federal and state tax net operating loss carryovers		91,788				113,522
	Net Profits Plan liability		20,913				29,233
	Stock compensation		18,820				18,026
	Other long-term liabilities		13,341				16,739
	Total deferred tax assets		144,862				177,520
	Valuation allowance		(5,001		)		(5,315		)
	Net deferred tax assets		139,861				172,205
	Total net deferred tax liabilities		639,376				528,804
	Less: current deferred income tax liabilities		(172		)		(5,442		)
	Add: current deferred income tax assets		10,921				14,021
	Non-current net deferred tax liabilities		$	650,125			$	537,383
	Current federal income tax refundable		$	4,630			$	2,511
	Current state income tax refundable		$	—			$	853
	Current state income tax payable		$	1,460			$	—
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	'
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Federal statutory tax expense (benefit)	$	97,514			$	(29,231	)		$	118,652
	Increase (decrease) in tax resulting from:
	State tax expense (benefit) (net of federal benefit)	9,400				(992		)		6,458
	Research and development credit	—				(970		)		(4,516		)
	Change in valuation allowance	(314		)		1,524				1,627
	Statutory depletion	(154		)		(210		)		(341		)
	Other	1,230				611				1,705
	Income tax expense (benefit)	$	107,676			$	(29,268	)		$	123,585
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]	'
	The total amount recorded for unrecognized tax benefits is presented below:
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Beginning balance	$	2,278			$	1,961			$	807
	Additions based on tax positions related to current year	—				—				1,172
	Additions for tax positions of prior years	80				317				183
	Reductions for lapse of statute of limitations	—				—				(201		)
	Ending balance	$	2,358			$	2,278			$	1,961

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Schedule of Borrowing Base Utilization, Credit Facility [Table Text Block]	'
	Interest and commitment fees are accrued based on the borrowing base utilization grid below.  Eurodollar loans accrue interest at the London Interbank Offered Rate plus the applicable margin from the utilization table below, and Alternate Base Rate (“ABR”) and swingline loans accrue interest at Prime plus the applicable margin from the utilization table below.  Commitment fees are accrued on the unused portion of the aggregate commitment amount and are included in interest expense in the accompanying statements of operations.
	Borrowing Base Utilization Grid
	Borrowing Base Utilization Percentage		<25%		≥25% <50%		≥50% <75%			≥75% <90%		≥90%
	Eurodollar Loans		1.5	%	1.75	%	2	%		2.25	%	2.5	%
	ABR Loans or Swingline Loans		0.5	%	0.75	%	1	%		1.25	%	1.5	%
	Commitment Fee Rate		0.375	%	0.375	%	0.5	%		0.5	%	0.5	%
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 February 12, 2014, December 31, 2013, and December 31, 2012:
		As of February 12, 2014			As of December 31, 2013			As of December 31, 2012
		(in millions)
	Credit facility balance	$	—		$	—		$	340
	Letters of credit (1)	$	0.8		$	0.8		$	0.8
	Available borrowing capacity	$	1,299.20		$	1,299.20		$	659.2
	(1) Letters of credit reduce the amount available under the credit facility on a dollar-for-dollar basis.
Schedule of Long-Term Debt [Table Text Block]	'
	The Senior Notes line on the accompanying balance sheets, as of December 31, 2013, and 2012, consisted of the following:
		As of December 31,
		2013			2012
		(in thousands)
	6.625% Senior Notes due 2019	$	350,000		$	350,000
	6.50% Senior Notes due 2021	350,000			350,000
	6.50% Senior Notes due 2023	400,000			400,000
	5.0% Senior Notes due 2024	500,000			—
	Total long-term debt	$	1,600,000		$	1,100,000
Schedule of Debt Instrument Redemption Price, 5% Senior Notes Due 2024 [Table Text Block]	'
	On or after July 15, 2018, the Company may also redeem all or, from time to time, a portion of the 2024 Notes at the redemption prices set forth below, during the twelve-month period beginning on July 15 of each applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2018	102.5	%
	2019	101.677	%
	2020	100.833	%
	2021 and thereafter	100	%
Schedule of Debt Instrument Redemption Price, 6.50% Senior Notes Due 2023 [Table Text Block]	'
	On or after July 1, 2017, the Company may also redeem all or, from time to time, a portion of the 2023 Notes at the redemption prices set forth below, during the twelve-month period beginning on July 1 of each applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2017	103.25	%
	2018	102.167	%
	2019	101.083	%
	2020 and thereafter	100	%
Schedule of Debt Instrument, Redemption Price, 6.50% Senior Notes Due 2021 [Table Text Block]	'
	The Company may also redeem all or, from time to time, a portion of the 2021 Notes on or after November 15, 2016, at the prices set forth below, during the twelve-month period beginning on November 15 of the applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2016	103.25	%
	2017	102.167	%
	2018	101.083	%
	2019 and thereafter	100	%
Schedule of Debt Instrument, Redemption Price, 6.625% Senior Notes Due 2019 [Table Text Block]	'
	The Company may also redeem all or, from time to time, a portion of the 2019 Notes on or after February 15, 2015, at the prices set forth below, during the twelve-month period beginning on February 15 of the applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:
	2015	103.313	%
	2016	101.656	%
	2017 and thereafter	100	%

Commitments_and_Contingencies_

Commitments and Contingencies Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Long-term Purchase Commitment [Table Text Block]	'
	The annual minimum payments for the next five years and total minimum lease payments thereafter are presented below:
	Years Ending December 31,	(in thousands)
	2014	$	179,118
	2015	147,119
	2016	144,438
	2017	132,559
	2018	128,418
	Thereafter	481,947
	Total	$	1,213,599

Compensation_Plans_Tables

Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2013
Compensation Related Costs [Abstract]	'
Schedule of performance share awards under equity incentive compensation plan	'																[1]
	A summary of the status and activity of non-vested PSUs is presented in the following table:
		For the Years Ended December 31,
		2013						2012					2011
		PSUs		Weighted-Average Grant-Date Fair Value				PSUs			Weighted-Average Grant-Date Fair Value		PSUs		Weighted-Average Grant-Date Fair Value
	Non-vested at beginning of year(1)	669,308		$	63.91			885,894			$	57.52	1,110,666		$	39.48
	Granted(1)	274,831		$	64.13			314,853			$	51.98	266,282		$	91.45
	Vested(1)	(345,005	)	$	60.06			(493,679	)		$	44.72	(364,172	)	$	35.74
	Forfeited(1)	(26,665	)	$	69.74			(37,760	)		$	65.35	(126,882	)	$	33.32
	Non-vested at end of year(1)	572,469		$	66.07			669,308			$	63.91	885,894		$	57.52
	-1	The number of awards assumes a one multiplier. The final number of shares of common stock issued may vary depending on the ending three-year performance multiplier, which ranges from zero to two.
Schedule of restricted stock unit incentive program under equity incentive compensation plan	'
	A summary of the status and activity of non-vested RSUs is presented below:
		For the Years Ended December 31,
		2013						2012					2011
		RSUs		Weighted-				RSUs			Weighted-		RSUs		Weighted-
				Average							Average				Average
				Grant-Date							Grant-Date				Grant-Date
				Fair Value							Fair Value				Fair Value
	Non-vested at beginning of year	496,244		$	51.81			308,877			$	44.33	333,359		$	31.16
	Granted	329,939		$	60.01			379,332			$	49.47	98,952		$	72.69
	Vested	(207,376	)	$	49.73			(166,672	)		$	32.72	(105,820	)	$	30.61
	Forfeited	(38,376	)	$	54.37			(25,293	)		$	51.06	(17,614	)	$	36.8
	Non-vested at end of year	580,431		$	57.05			496,244			$	51.81	308,877		$	44.33
Schedule of stock option grants under prior stock option plans	'
	A summary of activity associated with the Company’s Stock Option Plans during the last three years is presented in the following table:
				Weighted -
				Average				Aggregate
				Exercise				Intrinsic
		Shares		Price				Value
	For the year ended December 31, 2011
	Outstanding, start of year	920,765		$	13.11
	Exercised	(412,551	)	$	12.19			$	24,359,240
	Forfeited	—		$	—
	Outstanding, end of year	508,214		$	13.86			$	30,109,110
	Vested and exercisable at end of year	508,214		$	13.86			$	30,109,110
	For the year ended December 31, 2012
	Outstanding, start of year	508,214		$	13.86
	Exercised	(240,368	)	$	12.65			$	11,842,575
	Forfeited	—		$	—
	Outstanding, end of year	267,846		$	14.95			$	9,983,177
	Vested and exercisable at end of year	267,846		$	14.95			$	9,983,177
	For the year ended December 31, 2013
	Outstanding, start of year	267,846		$	14.95
	Exercised	(228,758	)	$	13.92			$	12,326,994
	Forfeited	—		$	—
	Outstanding, end of year	39,088		$	20.87			$	2,432,837
	Vested and exercisable at end of year	39,088		$	20.87			$	2,432,837
Schedule of options, vested and expected to vest	'																[1],[2]
	A summary of additional information related to options outstanding as of December 31, 2013, follows:
				Options Outstanding and Exercisable
				Number			Weighted-
				Of Options			Average
				Outstanding			Remaining
	Exercise			and			Contractual
	Price(1)			Exercisable			Life (in years)
	$	20.87		39,088			1
	Total			39,088
	(1) Exercise price is equal to the weighted average exercise price.
Schedule of employee stock purchase plan	'
	The fair value of ESPP shares issued during the periods reported were estimated using the following weighted-average assumptions:
		For the Years Ended December 31,
		2013		2012			2011
	Risk free interest rate	0.1	%	0.1	%		0.2	%
	Dividend yield	0.2	%	0.2	%		0.2	%
	Volatility factor of the expected market
	price of the Company’s common stock	41.1	%	47.8	%		36.3	%
	Expected life (in years)	0.5		0.5			0.5
Schedule of net profits plan cash payment allocation	'
	Cash payments made or accrued under the Net Profits Plan that have been recorded as either general and administrative expense or exploration expense are detailed in the table below:
		For the Years Ended December 31,
		2013			2012				2011
		(in thousands)
	General and administrative expense	$	13,734		$	15,565			$	19,326
	Exploration expense	1,310			1,751				2,091
	Total	$	15,044		$	17,316			$	21,417
[1]	The number of awards assumes a one multiplier. The final number of shares of common stock issued may vary depending on the ending three-year performance multiplier, which ranges from zero to two.
[2]	Exercise price is equal to the weighted average exercise price.

Pension_Benefits_Tables

Pension Benefits (Tables)	12 Months Ended
	Dec. 31, 2013																Dec. 31, 2012
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]	'																'
Schedule of Net Funded Status [Table Text Block]	'																'
		For the Years Ended December 31,
		2013				2012
		(in thousands)
	Change in benefit obligation:
	Projected benefit obligation at beginning of year	$	40,237			$	29,480
	Service cost	6,291				4,934
	Interest cost	1,627				1,374
	Plan amendments	—				—
	Actuarial loss (gain)	(1,577		)		5,467
	Benefits paid	(3,293		)		(1,018		)
	Projected benefit obligation at end of year	43,285				40,237
	Change in plan assets:
	Fair value of plan assets at beginning of year	20,254				13,940
	Actual return on plan assets	2,726				1,952
	Employer contribution	4,971				5,380
	Benefits paid	(3,293		)		(1,018		)
	Fair value of plan assets at end of year	24,658				20,254
	Funded status at end of year	$	(18,627	)		$	(19,983	)
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	'																'
	Information for Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets for Both Plans
		As of December 31,
		2013				2012
		(in thousands)
	Projected benefit obligation	$	43,285			$	40,237
	Accumulated benefit obligation	$	32,396			$	29,437
	Less: Fair value of plan assets	(24,658		)		(20,254		)
	Underfunded accumulated benefit obligation	$	7,738			$	9,183
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	'																'
	Pre-tax amounts not yet recognized in net periodic pension costs, but rather recognized in accumulated other comprehensive loss as of December 31, 2013 and 2012, consist of:
		As of December 31,
		2013				2012
		(in thousands)
	Unrecognized actuarial losses	$	8,439			$	12,427
	Unrecognized prior service costs	136				153
	Unrecognized transition obligation	—				—
	Accumulated other comprehensive loss	$	8,575			$	12,580
Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	'																'
	Pre-tax changes recognized in other comprehensive income (loss) during 2013, 2012, and 2011, were as follows:
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Net actuarial gain (loss)	$	2,766			$	(4,680	)		$	(3,014	)
	Prior service cost	—				—				(170		)
	Less: Amortization of:
	Prior service cost	(17		)		(17		)		—
	Actuarial loss	(1,222		)		(754		)		(405		)
	Total other comprehensive income (loss)	$	4,005			$	(3,909	)		$	(2,779	)
Components of the net periodic benefit cost for both the Qualified and the Nonqualified Pension Plan	'																'
	Components of Net Periodic Benefit Cost for Both Pension Plans
		For the Years Ended December 31,
		2013				2012				2011
		(in thousands)
	Components of net periodic benefit cost:
	Service cost	$	6,291			$	4,934			$	3,800
	Interest cost	1,627				1,374				1,184
	Expected return on plan assets that reduces periodic pension cost	(1,538		)		(1,165		)		(880		)
	Amortization of prior service cost	17				17				—
	Amortization of net actuarial loss	1,222				754				405
	Net periodic benefit cost	$	7,619			$	5,914			$	4,509
Schedule of Assumptions Used [Table Text Block]	'																'
	Weighted-average assumptions to measure the Company’s projected benefit obligation and net periodic benefit cost are as follows:
		As of December 31,
		2013		2012		2011
	Projected benefit obligation
	Discount rate	5.00%		3.90%		4.70%
	Rate of compensation increase	6.20%		6.20%		6.20%
	Net periodic benefit cost
	Discount rate	3.90%		4.70%		5.30%
	Expected return on plan assets	7.50%		7.50%		7.50%
	Rate of compensation increase	6.20%		6.20%		6.20%
Schedule of Allocation of Plan Assets [Table Text Block]	'																'
	The weighted-average asset allocation of the Qualified Pension Plan is as follows:
		Target			As of December 31,
	Asset Category	2014			2013			2012
	Equity securities	44	%		43.6	%		42.7	%
	Debt securities	33	%		32.2	%		32.8	%
	Other	23	%		24.2	%		24.5	%
	Total	100	%		100	%		100	%
Schedule of Pension Plan Assets Measured at Fair Value, Heirarchy and Asset Allocation [Table Text Block]	'																'
																	The fair value of the Company’s pension plan assets as of December 31, 2012, is as follows:
	The fair value of the Company’s Qualified Pension Plan assets as of December 31, 2013, utilizing the fair value hierarchy discussed in Note 11 – Fair Value Measurements is as follows:
																						Fair Value Measurements Using:
									Fair Value Measurements Using:									Actual Asset Allocation		Total		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
		Actual Asset Allocation			Total				Level 1 Inputs				Level 2 Inputs		Level 3 Inputs
																				(in thousands)
					(in thousands)												Cash and Money Market Funds	3.8	%	$	778	$	778	$	—	$	—
	Cash	—	%		$	—			$	—			$	—	$	—
																	Equity Securities
	Equity Securities
																	Domestic (1)	29.2	%	5,920		5,920		—		—
	Domestic (1)	29.9	%		7,371				4,888				2,483		—
																	International (2)	13.5	%	2,740		2,740		—		—
	International (2)	13.7	%		3,373				3,373				—		—
																	Total Equity Securities	42.7	%	8,660		8,660		—		—
	Total Equity Securities	43.6	%		10,744				8,261				2,483		—
																	Fixed Income Securities
	Fixed Income Securities
																	High-Yield Bonds (3)	6.1	%	1,240		1,240		—		—
	High-Yield Bonds (3)	5.9	%		1,448				1,448				—		—
																	Core Fixed Income (4)	20.8	%	4,204		4,204		—		—
	Core Fixed Income (4)	20.3	%		5,006				5,006				—		—
																	Floating Rate Corp Loans (5)	5.9	%	1,186		1,186		—		—
	Floating Rate Corp Loans (5)	6	%		1,483				1,483				—		—
																	Total Fixed Income Securities	32.8	%	6,630		6,630		—		—
	Total Fixed Income Securities	32.2	%		7,937				7,937				—		—
																	Other Securities:
	Other Securities:																Commodities (6)	3.3	%	669		669		—		—
	Commodities (6)	3.8	%		945				945				—		—		Real Estate (7)	3.9	%	783		—		—		783
	Real Estate (7)	3.5	%		859				—				—		859		Hedge Fund (8)	13.5	%	2,734		1,133		—		1,601
	Hedge Fund (8)	14.3	%		3,517				955				—		2,562		Total Other Securities	20.7	%	4,186		1,802		—		2,384
	Collective Investment Trusts (9)	2.6	%		656				—				656		—		Total Investments	100	%	$	20,254	$	17,870	$	—	$	2,384
	Total Other Securities	24.2	%		5,977				1,900				656		3,421
																	-1	Equity securities of United States large and small capitalization companies, which are actively traded securities that can be sold upon demand.
	Total Investments	100	%		$	24,658			$	18,098			$	3,139	$	3,421
																	-2	International equity securities consists of a well-diversified portfolio of holdings of mostly large issuers organized in developed countries with liquid markets, commingled with investments in equity securities of issuers located in emerging markets and believed to have strong sustainable financial productivity at attractive valuations.
	-1	Level 1 equity securities consist of United States large and small capitalization companies, which are actively traded securities that can be sold upon demand. Level 2 equity securities are investments in a collective investment fund that is valued at net asset value based on the value of the underlying investments and total units outstanding on a daily basis. The objective of this fund is to approximate the S&P 500 by investing in one or more collective investment funds.															-3	High-yield bonds consist of non-investment grade fixed income securities. The investment objective is to obtain high current income. Due to the increased level of default risk, security selection focuses on credit-risk analysis.
	-2	International equity securities consists of a well-diversified portfolio of holdings of mostly large issuers organized in developed countries with liquid markets, commingled with investments in equity securities of issuers located in emerging markets and believed to have strong sustainable financial productivity at attractive valuations.															-4	The objective is to achieve value added from sector or issue selection by constructing a portfolio to approximate the investment results of the Barclay's Capital Aggregate Bond Index with a modest amount of variability in duration around the index.
	-3	High-yield bonds consist of non-investment grade fixed income securities. The investment objective is to obtain high current income. Due to the increased level of default risk, security selection focuses on credit-risk analysis.															-5	Investments consist of floating rate bank loans. The interest rates on these loans are typically reset on a periodic basis to account for changes in the level of interest rates.
	-4	The objective is to achieve value added from sector or issue selection by constructing a portfolio to approximate the investment results of the Barclay's Capital Aggregate Bond Index with a modest amount of variability in duration around the index.															-6	Investments with exposure to commodity price movements, primarily through the use of futures, swaps and other commodity-linked securities.
	-5	Investments consist of floating rate bank loans. The interest rates on these loans are typically reset on a periodic basis to account for changes in the level of interest rates.															-7	The investment objective of direct real estate is to provide current income with the potential for long-term capital appreciation. Ownership in real estate entails a long-term time horizon, periodic valuations, and potentially low liquidity.
	-6	Investments with exposure to commodity price movements, primarily through the use of futures, swaps and other commodity-linked securities.															-8	The hedge fund portfolio includes an investment in an actively traded global mutual fund that focuses on alternative investments and a hedge fund of funds that invests both long and short using a variety of investment strategies.
	-7	The investment objective of direct real estate is to provide current income with the potential for long-term capital appreciation. Ownership in real estate entails a long-term time horizon, periodic valuations, and potentially low liquidity.
	-8	The hedge fund portfolio includes an investment in an actively traded global mutual fund that focuses on alternative investments and a hedge fund of funds that invests both long and short using a variety of investment strategies.
	-9	Collective investment trusts invest in short-term investments and are valued at the net asset value of the collective investment trust. The net asset value, as provided by the trustee, is used as a practical expedient to estimate fair value. The net asset value is based on the fair value of the underlying investments held by the fund less its liabilities.
Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block]	'																'
	Included below is a summary of the changes in Level 3 plan assets (in thousands):																Included below is a summary of the changes in Level 3 plan assets (in thousands):
	31-Dec-12	$	2,384														31-Dec-11	$	—
	Purchases	742															Purchases	2,329
	Realized gain on assets	161															Investment Returns	55
	Unrealized gain on assets	134															31-Dec-12	$	2,384
	31-Dec-13	$	3,421
Schedule of Expected Benefit Payments [Table Text Block]	'																'
	Expected benefit payments over the next 10 years are as follows:
	Years Ending December 31,		(in thousands)
	2014		$	2,120
	2015		$	2,837
	2016		$	3,287
	2017		$	3,993
	2018		$	4,407
	2019 through 2023		$	33,031

Asset_Retirement_Obligations_R

Asset Retirement Obligations Reconciliation of Asset Retirement Obligation Liability (Tables)	12 Months Ended
	Dec. 31, 2013
Asset Retirement Obligation [Abstract]	'
Schedule of Change in Asset Retirement Obligation [Table Text Block]	'
	A reconciliation of the Company’s asset retirement obligation liability is as follows:
		As of December 31,
		2013			2012
		(in thousands)
	Beginning asset retirement obligation	$	120,518		$	95,906
	Liabilities incurred	18,682			13,050
	Liabilities settled	(33,129		)	(8,101		)
	Accretion expense	5,997			4,679
	Revision to estimated cash flows	9,118			14,984
	Ending asset retirement obligation	$	121,186		$	120,518

Derivative_Financial_Instrumen2

Derivative Financial Instruments (Tables)	1 Months Ended				12 Months Ended
	Feb. 12, 2014				Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'				'
Schedule of Notional Amounts of Outstanding Derivative Positions	'				'
	Commodity Derivative Contracts Entered into After December 31, 2013				The following tables summarize the approximate volumes and average contract prices of contracts the Company had in place as of December 31, 2013:
					Oil Contracts
	The following tables summarize all commodity derivative contracts entered between January 1, 2014 and February 12, 2014:				Oil Swaps
	Gas Contracts
	Gas Swaps				Contract Period		Volumes			Weighted-
										Average
										Contract
	Contract Period	Volumes	Weighted-							Price
			Average				(Bbls)			(per Bbl)
			Contract		First quarter 2014		2,600,000			$	96.92
			Price
		(MMBtu)	(per MMBtu)		Second quarter 2014		2,373,000			$	94.95
	First quarter 2014	261,000	$	4.39
					Third quarter 2014		973,000			$	95.25
	Second quarter 2014	365,000	$	3.84
					Fourth quarter 2014		891,000			$	95.16
	Third quarter 2014	341,000	$	3.89
					2015		2,911,000			$	89.06
	Fourth quarter 2014	321,000	$	3.97
					2016		2,704,000			$	85.19
	2015	1,133,000	$	3.72
					All oil swaps*		12,452,000
	2016	69,000	$	4.12
					*Oil swaps are comprised of NYMEX WTI (97%) and Argus LLS (3%).
	All gas swaps*	2,490,000
					Oil Collars
	*Natural gas swaps are comprised of IF NNG Ventura (30%) and IF CIG N System (70%).
	NGL Contracts
	NGL Swaps				Contract Period		NYMEX WTI			Weighted-				Weighted-
							Volumes			Average				Average
										Floor				Ceiling
	Contract Period	Volumes	Weighted-							Price				Price
			Average				(Bbls)			(per Bbl)				(per Bbl)
			Contract		First quarter 2014		694,000			$	80.97			$	115.07
			Price
		(Bbls)	(per Bbl)		Second quarter 2014		431,000			$	85			$	102.5
	First quarter 2014	516,000	$	54.85
					Third quarter 2014		973,000			$	85			$	102.58
	Second quarter 2014	531,000	$	52.53
					Fourth quarter 2014		923,000			$	85			$	102.63
	Third quarter 2014	416,000	$	52.47
					2015		3,366,000			$	85			$	94.25
	Fourth quarter 2014	334,000	$	52.52
					All oil collars		6,387,000
	All NGL swaps*	1,797,000
					Natural Gas Contracts
	*NGL swaps are comprised of OPIS Natural Gasoline Mt Belv Non TET (17%) and OPIS Propane Mt Belv TET (83%).
					Gas Swaps
					Contract Period		Volumes			Weighted-
										Average
										Contract
										Price
							(MMBtu)			(per MMBtu)
					First quarter 2014		33,651,000			$	4.25
					Second quarter 2014		25,729,000			$	3.96
					Third quarter 2014		26,398,000			$	4.01
					Fourth quarter 2014		23,965,000			$	4.01
					2015		63,317,000			$	4.03
					2016		39,014,000			$	4.18
					2017		23,430,000			$	4.21
					2018		10,200,000			$	4.31
					All gas swaps*		245,704,000
					*Natural gas swaps are comprised of IF El Paso Permian (3%), IF HSC (77%), IF NGPL TXOK (3%), IF NNG Ventura (2%), IF PEPL (6%), IF Reliant N/S (8%), and IF NGPL MidCon (1%).
				Gas Collars
				Contract Period		Volumes			Weighted-				Weighted-
									Average				Average
									Floor				Ceiling
									Price				Price
						(MMBtu)			(per MMBtu)				(per MMBtu)
				First quarter 2014		1,540,000			$	4.39			$	5.58
				Second quarter 2014		4,194,000			$	4.38			$	5.29
				2015		14,480,000			$	3.96			$	4.3
				All gas collars*		20,214,000
				*Natural gas collars are comprised of IF El Paso Permian (2%), IF HSC (57%), IF NGPL TXOK (3%), IF NNG Ventura (5%), IF PEPL (7%), IF Reliant N/S (14%), and IF TETCO STX (12%).
				NGL Contracts
				NGL Swaps
				Contract Period		Volumes			Weighted-
									Average
									Contract
									Price
						(Bbls)			(per Bbl)
				First quarter 2014		913,000			$	59.72
				Second quarter 2014		565,000			$	63.22
				Third quarter 2014		544,000			$	62.34
				Fourth quarter 2014		527,000			$	61.57
				All NGL swaps*		2,549,000
				*NGL swaps are comprised of OPIS IsoButane Mt Belv Non TET (2%), OPIS Natural Gasoline Mt Belv Non TET (34%), OPIS NButane Mt Belv Non TET (3%), and OPIS Propane Mt Belv TET (61%).
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 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
						As of December 31, 2012
						Derivative Assets						Derivative Liabilities
						Balance Sheet		Fair Value				Balance Sheet		Fair Value
						Classification						Classification
						(in thousands)
					Commodity Contracts	Current assets		$	37,873			Current liabilities		$	8,999
					Commodity Contracts	Noncurrent assets		16,466				Noncurrent liabilities		6,645
					Derivatives not designated as hedging instruments			$	54,339					$	15,644
Schedule of the potential effects of master netting arrangements	'				'
					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 December 31,								As of December 31,
					Offsetting of Derivative Assets and Liabilities		2013				2012				2013				2012
							(in thousands)
					Gross amounts presented in the accompanying balance sheets		$	52,510			$	54,339			$	(31,020	)		$	(15,644	)
					Amounts not offset in the accompanying balance sheets		(30,652		)		(13,400		)		30,652				13,400
					Net amounts		$	21,858			$	40,939			$	(368	)		$	(2,244	)
Schedule of unrealized and realized gains and losses on derivative instruments in the statement of operations	'				'
					The following table summarizes the components of derivative (gain) loss presented in the accompanying statements of operations:
						For the Years Ended December 31,
						2013				2012				2011
						(in thousands)
					Derivative cash settlement (gain) loss:
					Oil contracts	$	15,161			$	11,893			$	22,633
					Gas contracts	(30,338		)		(47,270		)		(10,711		)
					NGL contracts	(6,885		)		(8,887		)		13,749
					Total derivative cash settlement (gain) loss (1)	(22,062		)		(44,264		)		25,671
					Derivative (gain) loss:
					Oil contracts	(496		)		(31,981		)		(3,391		)
					Gas contracts	16,285				31,777				(64,310		)
					NGL contracts	3,193				(11,162		)		4,944
					Total derivative gain (2)	$	(3,080	)		$	(55,630	)		$	(37,086	)
					(1)	Total derivative cash settlement gain (loss) is reported in the derivative cash settlement gain (loss) line item on the consolidated statements of cash flows within net cash provided by operating activities.
					(2)	Total derivative gain is reported in the derivative gain line item on the consolidated statements of cash flows within net cash provided by operating activities.
Detail of the effect of derivative instruments reclassified from AOCI to the statement of operations (net of income tax)	'				'
					The following table details the effect of derivative instruments on AOCIL and the accompanying statements of operations (net of income tax):
								Location on		For the Years Ended December 31,
								Accompanying
								Statements of
						Derivatives		Operations		2013				2012				2011
										(in thousands)
					Amount reclassified from AOCIL	Commodity Contracts		Realized hedge gain (loss)		$	1,115			$	(2,264	)		$	12,997

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	'										[1],[2]
	The following table is a listing of the Company’s assets and liabilities that are measured at fair value and where they were classified 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 that is measured at fair value on a nonrecurring basis.
	The following table is a listing of the Company’s assets and liabilities that are measured at fair value and where they were classified within the hierarchy as of December 31, 2012:
		Level 1			Level 2			Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	54,339		$	—
	Proved oil and gas properties (2)	$	—		$	—		$	209,959
	Unproved oil and gas properties (2)	$	—		$	—		$	42,765
	Liabilities:
	Derivatives (1)	$	—		$	15,644		$	—
	Net Profits Plan (1)	$	—		$	—		$	78,827
	(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 that is measured at fair value on a nonrecurring basis.
Schedule of reconciliation of fair value measurements using Level 3 inputs	'
	The following table reflects the activity for the Company’s Net Profits Plan liability measured at fair value using Level 3 inputs:
		For the Years Ended December 31,
		2013			2012			2011
		(in thousands)
	Beginning balance	$	78,827		$	107,731		$	135,850
	Net increase (decrease) in liability (1)	3,527			(9,251		)	2,269
	Net settlements (1) (2) (3)	(25,369		)	(19,653		)	(30,388		)
	Transfers in (out) of Level 3	—			—			—
	Ending balance	$	56,985		$	78,827		$	107,731
	-1	Net changes in the 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 amounts in the table include cash payments made or accrued under the Net Profits Plan of $10.3 million, $2.3 million, and $6.3 million relating to divestiture proceeds for the years ended December 31, 2013, 2012, and 2011, respectively.
	-3	During 2011, the Company elected to cash out several Net Profits Plan pools with a $2.6 million direct payment. As a result, the Company reduced its Net Profits Plan liability by that amount.  There was no impact on the accompanying statements of operations for the period ended December 31, 2011, related to these settlements.
Schedule of Long-term Debt Instruments [Table Text Block]	'
	The following table reflects the fair value of the Senior Notes measured at fair value 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 December 31, 2013 or 2012, as they are recorded at historical value.
		As of December 31,
		2013			2012
		(in thousands)
	2019 Notes	$	374,290		$	371,875
	2021 Notes	$	373,625		$	371,070
	2023 Notes	$	422,000		$	424,200
	2024 Notes (1)	$	475,315		$	—
	(1) The 2024 Notes were issued on May 20, 2013.
[1]	This represents a non-financial asset 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.

Suspended_Well_Costs_Tables

Suspended Well Costs (Tables)	12 Months Ended
	Dec. 31, 2013
Suspended Well Costs [Abstract]	'
Capitalized Exploratory Well Costs, Roll Forward [Table Text Block]	'
	The following table reflects the net changes in capitalized exploratory well costs during 2013, 2012, and 2011. The table does not include amounts that were capitalized and either subsequently expensed or reclassified to producing well costs in the same year:
		For the Years Ended December 31,
		2013			2012			2011
		(in thousands)
	Beginning balance on January 1,	$	9,100		$	18,600		$	35,862
	Additions to capitalized exploratory well costs pending the determination of proved reserves	34,527			9,100			15,618
	Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	(9,100		)	(5,865		)	(32,880		)
	Capitalized exploratory well costs charged to expense	—			(12,735		)	—
	Ending balance at December 31,	$	34,527		$	9,100		$	18,600
Schedule of Aging of Capitalized Exploratory Well Costs [Table Text Block]	'
	The following table provides an aging of capitalized exploratory well costs based on the date the drilling was completed and the number of projects for which exploratory well costs have been capitalized for more than one year since the completion of drilling:
		As of December 31,
		2013			2012			2011
		(in thousands)
	Exploratory well costs capitalized for one year or less	$	34,527		$	9,100		$	15,618
	Exploratory well costs capitalized for more than one year	—			—			2,982
	Ending balance at December 31,	$	34,527		$	9,100		$	18,600
	Number of projects with exploratory well costs that have been capitalized more than a year	—			—			2

Summary_of_Significant_Account3

Summary of Significant Accounting Policies Other (Details) (USD $)

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2012

Regency Gas Services, LLC [Member]

Regency Gas Services, LLC [Member]

Regency Gas Services, LLC [Member]

Anadarko Petroleum Company [Member]

Plains Marketing, LP [Member]

Plains Marketing, LP [Member]

Convertible Debt [Member]

Convertible Debt [Member]

Convertible Debt [Member]

Line of Credit [Member]

Line of Credit [Member]

Basis of Presentation and Significant Accounting Policies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revolving credit facility

$0

$340,000,000

'

'

'

'

'

'

'

'

'

'

$0

$340,000,000

Concentration of Credit Risk and Major Customers [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Major Customers

3

2

1

'

'

'

'

'

'

'

'

'

'

'

Entity-Wide Revenue, Major Customer, Percentage

'

'

'

26.00%

21.00%

18.00%

16.00%

12.00%

13.00%

'

'

'

'

'

Number of Counterparties Downgraded

3

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Derivative Counterparties

10

'

'

'

'

'

'

'

'

'

'

'

'

'

Property, Plant and Equipment [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property, Plant, and Equipment, Salvage Value

57,500,000

64,400,000

'

'

'

'

'

'

'

'

'

'

'

'

Inventory, Net [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Raw Materials Inventory

16,000,000

13,400,000

'

'

'

'

'

'

'

'

'

'

'

'

Property, Plant and Equipment, Estimated Useful Lives

'three to thirty years

'

'

'

'

'

'

'

'

'

'

'

'

'

Goodwill and Intangible Assets Disclosure [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Intangible Assets, Net (Excluding Goodwill)

10,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenues [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenue Receipt, Days After Sale, Low End of Range

30

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenue Receipt, Days After Sale, High End of Range

90

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment of Proved Properties [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

5

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment of proved properties

172,641,000

208,923,000

219,037,000

'

'

'

'

'

'

'

'

'

'

'

Abandonment and impairment of unproved properties

46,105,000

16,342,000

7,367,000

'

'

'

'

'

'

'

'

'

'

'

Debt Instruments [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Interest Rate, Stated Percentage

'

'

'

'

'

'

'

'

'

3.50%

3.50%

3.50%

'

'

Debt Instrument, Convertible, Conversion Price

'

'

'

'

'

'

'

'

'

$54.42

'

'

'

'

Debt Instrument, Principal Amount Denominator for Conversion into Common Stock

'

'

'

'

'

'

'

'

'

1,000

'

'

'

'

Debt instrument convertible conversion rate

'

'

'

'

'

'

'

'

'

864,106

'

'

'

'

Capitalization of Development and Implementation of Internal Use Software

$11,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies Earnings Per Share (Details) (USD $)	12 Months Ended						12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2010	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
				Convertible Debt [Member]	Convertible Debt [Member]	Convertible Debt [Member]	Retained Earnings	Retained Earnings	Retained Earnings
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]	'	'	'	'	'	'	'	'	'
Debt Instrument, Interest Rate, Stated Percentage	'	'	'	3.50%	3.50%	3.50%	'	'	'
Debt instrument convertible conversion rate	'	'	'	864,106	'	'	'	'	'
Debt Instrument, Principal Amount Denominator for Conversion into Common Stock	'	'	'	$1,000	'	'	'	'	'
Debt Instrument, Convertible, Conversion Price	'	'	'	$54.42	'	'	'	'	'
Weighted Average Number Diluted Shares Outstanding Adjustment	1,383,000	0	3,809,000	'	'	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	2,102,000	0	'	'	'	'	'	'
Earnings Per Share Reconciliation [Abstract]	'	'	'	'	'	'	'	'	'
Net Income (loss)	$170,935,000	($54,249,000)	$215,416,000	'	'	'	$170,935,000	($54,249,000)	$215,416,000
Weighted Average Number of Shares Outstanding, Basic	66,615,000	65,138,000	63,755,000	'	'	'	'	'	'
Incremental Common Shares Attributable to Share-based Payment Arrangements	1,383,000	0	2,592,000	'	'	'	'	'	'
Incremental Common Shares Attributable to Conversion of Debt Securities	0	0	1,217,000	'	'	'	'	'	'
Weighted Average Number of Shares Outstanding, Diluted	67,998,000	65,138,000	67,564,000	'	'	'	'	'	'
Basic net income (loss) per common share	$2.57	($0.83)	$3.38	'	'	'	'	'	'
Diluted net income (loss) per common share	$2.51	($0.83)	$3.19	'	'	'	'	'	'

Summary_of_Significant_Account5

Summary of Significant Accounting Policies Other Comprehensive Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Other comprehensive income [Abstract]	'		'		'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Reclassification to Earnings, before Tax	$1,777		($3,865)		$20,707
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Reclassification to Earnings, Tax	-662		1,601		-7,710
Reclassification to earnings	1,115		-2,264		12,997
Other Comprehensive Income (Loss), Minimum Pension Liability Net Adjustment, before Tax	4,005		-3,909		-2,779
Other Comprehensive Income (Loss), Minimum Pension Liability, Tax	1,522		-1,439		-984
Pension liability adjustment	$2,483	[1]	($2,470)	[1]	($1,795)	[1]
[1]	mounts are reclassified to General and administrative expense on the Company's consolidated statements of operations. The net of tax effect of the reclassification was approximately $768,000 in 2013. The accompan

Accounts_Receivable_and_Accoun2

Accounts Receivable and Accounts Payable and Accrued Expenses Accounts Receivable (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable	'	'
Accounts Receivable, Net, Current	$318,371	$254,805
Accrued oil, gas, and NGL production revenue	'	'
Accounts, Notes, Loans and Financing Receivable	'	'
Accounts Receivable, Net, Current	228,169	160,568
Amounts due From Joint Interest Owner	'	'
Accounts, Notes, Loans and Financing Receivable	'	'
Accounts Receivable, Net, Current	37,517	42,740
Acquisition and Development Agreement receivable	'	'
Accounts, Notes, Loans and Financing Receivable	'	'
Accounts Receivable, Net, Current	0	19,931
State severance tax refunds	'	'
Accounts, Notes, Loans and Financing Receivable	'	'
Accounts Receivable, Net, Current	29,213	17,237
Other	'	'
Accounts, Notes, Loans and Financing Receivable	'	'
Accounts Receivable, Net, Current	$23,472	$14,329

Accounts_Receivable_and_Accoun3

Accounts Receivable and Accounts Payable and Accrued Expenses Accounts Payable and Accrued Expenses (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts Payable and Accrued Expenses	'	'	'
Capital Expenditures Incurred but Not yet Paid	$217,820	$262,800	$214,800
Accounts payable and accrued expenses	606,751	525,627	'
Accrued Drilling Costs	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	'	243,611	'
Revenue and Severence Taxes Payable	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	87,852	65,494	'
Accrued Lease Operating Expense	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	29,296	28,037	'
Accrued property taxes	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	10,401	9,478	'
Joint Owner Advances	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	96,636	69,639	'
Accrued Compensation Costs	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	71,466	35,607	'
Accrued interest	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	40,027	25,027	'
Other	'	'	'
Accounts Payable and Accrued Expenses	'	'	'
Accounts payable and accrued expenses	$53,253	$48,734	'

Divestitures_and_Assets_Held_f1

Divestitures and Assets Held for Sale (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]	'	'	'
Cash received on divestiture of non-strategic assets	($424,849,000)	($55,375,000)	($364,522,000)
Assets Held-for-sale, Current	'	'	'
Reasonably certain period within which sale will take place (in years)	1	'	'
Oil and gas properties held for sale, net of accumulated depletion, depreciation and amortization of $7,390 in 2013 and $20,676 in 2012	19,072,000	33,620,000	'
Asset Retirement Obligations Assets Held-for-sale Noncurrent	3,033,000	1,393,000	'
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	822,872,000	727,877,000	511,103,000
Gain (Loss) on Sale of Proved Property	-27,974,000	27,018,000	-220,676,000
Mid Continent and Rocky Mountain Region	'	'	'
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]	'	'	'
Cash received on divestiture of non-strategic assets	'	-57,900,000	'
Estimated gain on divestiture of assets	'	-7,400,000	'
South Texas and Gulf Coast Region	'	'	'
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]	'	'	'
Cash received on divestiture of non-strategic assets	'	'	-230,700,000
Estimated gain on divestiture of assets	'	'	-193,800,000
Mid-Continent Divestiture	'	'	'
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]	'	'	'
Cash received on divestiture of non-strategic assets	-370,300,000	'	-35,800,000
Estimated gain on divestiture of assets	-29,200,000	'	-28,500,000
Rocky Mountain Divestiture	'	'	'
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]	'	'	'
Cash received on divestiture of non-strategic assets	-56,300,000	'	-45,500,000
Estimated gain on divestiture of assets	10,100,000	'	-27,200,000
Permian Divestiture	'	'	'
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]	'	'	'
Cash received on divestiture of non-strategic assets	-14,500,000	'	'
Estimated gain on divestiture of assets	-6,500,000	'	'
Oil and Gas Properties	'	'	'
Assets Held-for-sale, Current	'	'	'
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	'	1,700,000	'
Gain (Loss) on Sale of Proved Property	'	$33,900,000	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
IRS Proposed R&D Tax Adjustment	$4,600,000	'	'
Excess tax benefit	0	0	0
Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority	4,000,000	'	'
Current portion of income tax expense (benefit):	'	'	'
Federal	0	0	-1,757,000
State	2,121,000	370,000	1,553,000
Deferred portion of income tax expense (benefit)	-105,555,000	29,638,000	-123,789,000
Income tax (expense) benefit	107,676,000	-29,268,000	123,585,000
Effective tax rate (as a percent)	38.60%	35.00%	36.50%
Excess income tax benefit from the exercise of stock awards	0	'	'
Deferred Income Taxes [Abstract]	'	'	'
Deferred Tax Liabilities, Oil and Gas Properties	768,463,000	678,624,000	'
Deferred Tax Liabilities, Derivative asset	9,529,000	15,942,000	'
Deferred Tax Liabilities, Other	1,245,000	6,443,000	'
Deferred Tax Liabilities	779,237,000	701,009,000	'
Deferred Tax Assets, Federal and state tax net operating loss carryovers	91,788,000	113,522,000	'
Deferred Tax Assets, Net Profits Plan Liability	20,913,000	29,233,000	'
Deferred Tax Assets, Stock compensation	18,820,000	18,026,000	'
Deferred Tax Assets, Other Long-term Liabilities	13,341,000	16,739,000	'
Deferred Tax Assets, Gross	144,862,000	177,520,000	'
Deferred Tax Assets, Valuation Allowance	-5,001,000	-5,315,000	'
Deferred Tax Assets, Net	139,861,000	172,205,000	'
Deferred Tax Liabilities, Net	639,376,000	528,804,000	'
Less: current deferred income tax liabilities	-172,000	-5,442,000	'
Add: current deferred income tax assets	10,921,000	14,021,000	'
Deferred income taxes; Net, non-current	650,125,000	537,383,000	'
Income Taxes Receivable, Current	4,630,000	3,364,000	'
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	376,100,000	'	'
Unrecognized Tax Benefits, Exercise of Stock Awards	126,700,000	'	'
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	147,500,000	'	'
Deferred Tax Assets, Tax Credit Carryforwards, Research	5,000,000	'	'
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]	'	'	'
Federal statutory tax expense (benefit)	97,514,000	-29,231,000	118,652,000
State tax expense (benefit) (net of federal benefit)	9,400,000	-992,000	6,458,000
Research and development credit	0	-970,000	-4,516,000
Change in valuation allowance	-314,000	1,524,000	1,627,000
Statutory depletion	-154,000	-210,000	-341,000
Other	1,230,000	611,000	1,705,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]	'	'	'
Unrecognized Tax Benefits, Beginning Balance	2,278,000	1,961,000	807,000
Unrecognized Tax Benefits, Additions based on tax positions related to current year	0	0	1,172,000
Unrecognized Tax Benefits, Additions For Tax Positions Of Prior Years	80,000	317,000	183,000
Unrecognized Tax Benefits,Reductions For Lapse Of Statute Of Limitations	0	0	-201,000
Unrecognized Tax Benefits, Ending Balance	2,358,000	2,278,000	1,961,000
Internal Revenue Service (IRS) [Member]	'	'	'
Deferred Income Taxes [Abstract]	'	'	'
Income Taxes Receivable, Current	4,630,000	2,511,000	'
State and Local Jurisdiction [Member]	'	'	'
Deferred Income Taxes [Abstract]	'	'	'
Income Taxes Receivable, Current	0	853,000	'
Taxes Payable, Current	1,460,000	0	'
Unrecognized Tax Benefit Possible Change, Minimum [Member]	'	'	'
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]	'	'	'
Unrecognized Tax Benefits, Ending Balance	0	'	'
Unrecognized Tax Benefit Possible Change, Maximum [Member]	'	'	'
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]	'	'	'
Unrecognized Tax Benefits, Ending Balance	$1,400,000	'	'

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Sep. 06, 2013

20-May-13

Apr. 12, 2013

Dec. 31, 2012

Dec. 31, 2013

20-May-13

Dec. 31, 2013

Jun. 28, 2012

Dec. 31, 2013

Dec. 31, 2012

Nov. 09, 2011

Dec. 31, 2013

Dec. 31, 2012

Feb. 07, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Feb. 12, 2014

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

5% Senior Notes Due 2024 [Member]

5% Senior Notes Due 2024 [Member]

6.50% Senior Notes Due 2023 [Member]

6.50% Senior Notes Due 2023 [Member]

6.50% Senior Notes Due 2021 [Member]

6.50% Senior Notes Due 2021 [Member]

6.50% Senior Notes Due 2021 [Member]

6.625% Senior Notes Due 2019 [Member]

6.625% Senior Notes Due 2019 [Member]

6.625% Senior Notes Due 2019 [Member]

3.50% Senior Convertible Notes

3.50% Senior Convertible Notes

3.50% Senior Convertible Notes

Less than 25%

More than 25% Less than 50%

More than 50% Less than 75%

More than 75% Less than 90%

More than 90%

Eurodollar Loans

Eurodollar Loans

Eurodollar Loans

Eurodollar Loans

Eurodollar Loans

Eurodollar Loans

ABR Loans or Swingline Loans

ABR Loans or Swingline Loans

ABR Loans or Swingline Loans

ABR Loans or Swingline Loans

ABR Loans or Swingline Loans

ABR Loans or Swingline Loans

2015 [Member]

2016 [Member]

2016 [Member]

2017 [Member]

2017 [Member]

2018 [Member]

2018 [Member]

2018 [Member]

2019 [Member]

2019 [Member]

2020 [Member]

2020 and Thereafter [Member]

2019 and Thereafter [Member]

2017 and Thereafter [Member]

2021 and Thereafter [Member]

Subsequent Event [Member]

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Less than 25%

More than 25% Less than 50%

More than 50% Less than 75%

More than 75% Less than 90%

More than 90%

Revolving Credit Facility

Less than 25%

More than 25% Less than 50%

More than 50% Less than 75%

More than 75% Less than 90%

More than 90%

6.625% Senior Notes Due 2019 [Member]

6.50% Senior Notes Due 2021 [Member]

6.625% Senior Notes Due 2019 [Member]

6.50% Senior Notes Due 2023 [Member]

6.50% Senior Notes Due 2021 [Member]

5% Senior Notes Due 2024 [Member]

6.50% Senior Notes Due 2023 [Member]

6.50% Senior Notes Due 2021 [Member]

5% Senior Notes Due 2024 [Member]

6.50% Senior Notes Due 2023 [Member]

5% Senior Notes Due 2024 [Member]

6.50% Senior Notes Due 2023 [Member]

6.50% Senior Notes Due 2021 [Member]

6.625% Senior Notes Due 2019 [Member]

5% Senior Notes Due 2024 [Member]

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Deferred financing fees

'

'

'

($3,400,000)

'

'

'

'

'

$9,800,000

'

$7,900,000

'

'

$6,900,000

'

'

$8,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum loan amount

'

'

'

2,500,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Current borrowing base

'

'

'

1,300,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Borrowing Base, Line of Credit

'

'

'

'

2,200,000,000

1,775,000,000

1,900,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reduction in Borrowing Base as a Percent of Senior Debt Prinicipal

'

'

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Interest Rate Description

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'London Interbank Offered Rate plus the applicable margin from the utilization table

'

'

'

'

'

'Prime plus the applicable margin from the utilization table

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.50%

1.75%

2.00%

2.25%

2.50%

'

0.50%

0.75%

1.00%

1.25%

1.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Commitment Fee Rate (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.38%

0.38%

0.50%

0.50%

0.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revolving credit facility

0

340,000,000

'

0

'

'

'

340,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

Letters of credit outstanding

'

'

'

800,000

[1]

'

'

'

800,000

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

800,000

[1]

Available Borrowing Capacity Under Credit Facility

'

'

'

1,299,200,000

'

'

'

659,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,299,200,000

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

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Long-term Debt

1,600,000,000

1,100,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum amount of dividend payments in any given calendar year under the covenants of the debt instrument

'

'

'

'

'

'

'

'

'

'

6,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Face Amount

'

'

'

'

'

'

'

'

'

500,000,000

'

400,000,000

'

'

350,000,000

'

'

350,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Interest Rate, Stated Percentage

'

'

'

'

'

'

'

'

'

5.00%

'

6.50%

'

'

6.50%

'

'

6.63%

3.50%

3.50%

3.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from Debt Issuance, Net of Issuance Costs, 5% Senior Notes

'

'

'

'

'

'

'

'

490,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net Proceeds from 6.50% Senior Notes due 2023

'

'

'

'

'

'

'

'

'

'

392,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net proceeds from debt issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

343,100,000

'

'

341,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum percentage of the principal amount of the debt instrument which the entity may redeem with proceeds from equity offerings in the first through third year following the issuance year (as a percent)

'

'

'

'

'

'

'

'

35.00%

'

35.00%

'

35.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Redemption price of debt instrument if redeemed with proceeds from qualified equity offerings in the first through third year following the issuance year (as a percent)

'

'

'

'

'

'

'

'

105.00%

'

106.50%

'

106.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Call Feature

'

'

'

'

'

'

'

'

'at a redemption price equal to 100 percent of the principal amount of the 2024 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date.B

'

'redemption price equal to 100 percent of the principal amount of the 2023 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date.

'

'redemption price equal to 100% of the principal amount, plus a specified make-whole premium and accrued and unpaid interest

'

'

'redemption price equal to 100% of the principal amount, plus a specified make-whole premium and accrued and unpaid interest

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Early Debt Redemption, Redemption Price as a Percent of Face Amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

103.31%

103.25%

101.66%

103.25%

102.17%

102.50%

102.17%

101.08%

101.68%

101.08%

100.83%

100.00%

100.00%

100.00%

100.00%

'

Debt Conversion, Converted Instrument, Amount

'

2,641,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

281,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt instrument convertible conversion rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

864,106

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Repayments of Convertible Debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest Costs, Capitalized During Period

$11,000,000

$12,100,000

$10,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

Letters of credit reduce the amount available under the credit facility on a dollar-for-dollar basis.

Commitments_Details

Commitments (Details) (USD $)

12 Months Ended

9 Months Ended

12 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Drilling Rig Leasing Contracts

Gas gathering through-put commitments

Office Space Leases

Office Space Leases

Other miscellaneous contracts and leases

Natural Gas [Member]

Crude Oil [Member]

Shares Issued to the Board of Directors [Member]

Shares Issued to the Board of Directors [Member]

Shares Issued to the Board of Directors [Member]

Pending Litigation [Member]

MMcf

MMBbls

Commitments and Contingencies

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock-based compensation expense

$32,347,000

$30,185,000

$26,824,000

'

'

'

'

'

'

'

$1,400,000

$1,300,000

$1,200,000

'

Long-term Purchase Commitment, Amount

'

'

'

65,700,000

1,100,000,000

12,900,000

69,400,000

7,600,000

'

'

'

'

'

'

Long-term Purchase Commitment, Time Period

'12 years

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Obligation, Due in Next Twelve Months

179,118,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Obligation, Due in Second Year

147,119,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Obligation, Due in Third Year

144,438,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Obligation, Due in Fourth Year

132,559,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Obligation, Due in Fifth Year

128,418,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Obligation, Due after Fifth Year

481,947,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Commitment amount

1,213,599,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume

'

'

'

'

'

'

'

'

1,807,000,000,000

53,000,000

'

'

'

'

Operating Leases, Rent Expense

5,700,000

5,400,000

3,700,000

'

'

'

'

'

'

'

'

'

'

'

Other Commitment

33,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimated Litigation Liability

23,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Accounts Payable and Other Accrued Liabilities

'

'

'

'

'

'

'

'

'

'

'

'

'

9,600,000

Amount paid (related to litigation)

'

'

'

'

'

'

'

'

'

'

'

'

'

$13,500,000

Compensation_Plans_Stock_Based

Compensation Plans: Stock Based (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Equity Plan	'		'		'
Number of shares available for grant	3,800,000		'		'
Impact outright issuance of one share has on number of available shares	1		'		'
Impact of issuance of one performance share award on available shares under the equity incentive plan	2		'		'
Director Shares	'		'		'
Stock-based compensation expense	$32,347,000		$30,185,000		$26,824,000
Shares Issued to the Board of Directors [Member]	'		'		'
Director Shares	'		'		'
Stock issued from treasury to non-employee directors (in shares)	28,169		30,486		21,568
Stock-based compensation expense	1,400,000		1,300,000		1,200,000
Performance Shares [Member]	'		'		'
Equity Plan	'		'		'
Unrecognized stock based compensation expense	18,800,000		'		'
RSUs	'		'		'
Non-vested at the beginning of the period (in shares)	669,308	[1]	885,894	[1]	1,110,666	[1]
Granted (in shares)	274,831	[1]	314,853	[1]	266,282	[1]
Vested (in shares)	-345,005	[1]	-493,679	[1]	-364,172	[1]
Forfeited (in shares)	-26,665	[1]	-37,760	[1]	-126,882	[1]
Non-vested at the end of the period (in shares)	572,469	[1]	669,308	[1]	885,894	[1]
Weighted Average Grant Date Fair Value	'		'		'
Non-vested outstanding at the beginning of the period (in dollars per share)	$63.91	[1]	$57.52	[1]	$39.48	[1]
Granted (in dollars per share)	$64.13	[1]	$51.98	[1]	$91.45	[1]
Vested (in dollars per share)	$60.06	[1]	$44.72	[1]	$35.74	[1]
Forfeited (in dollars per share)	$69.74	[1]	$65.35	[1]	$33.32	[1]
Non-vested outstanding at the end of the period (in dollars per share)	$66.07	[1]	$63.91	[1]	$57.52	[1]
Multiplier assumed	1		'		'
Performance measurement period	3		'		'
Common stock awards vesting multiplier, low end of range	0		'		'
Common stock awards vesting multiplier, high end of range	2		'		'
Fair value of PSUs/RSUs Granted in Period	17,600,000		16,400,000		24,300,000
PSU/RSU Vesting Increment	0.33		'		'
Fair value of PSUs/RSUs Vested in Period	20,700,000		22,100,000		13,000,000
Multiplier Applied to PSU Awards at Settlement	1.725		2		0.8
Stock issued for settlement, PSU, net of tax (in shares)	387,461		812,562		206,468
Shares held for settlement of income and payroll tax obligations (in shares)	200,050		406,866		98,955
Director Shares	'		'		'
Stock-based compensation expense	16,800,000		18,200,000		19,700,000
First Anniversary [Member] | Performance Shares [Member]	'		'		'
Weighted Average Grant Date Fair Value	'		'		'
PSU/RSU Vesting Increment	'		0.14		'
Second Anniversary [Member] | Performance Shares [Member]	'		'		'
Weighted Average Grant Date Fair Value	'		'		'
PSU/RSU Vesting Increment	'		0.29		'
Third Anniversary [Member] | Performance Shares [Member]	'		'		'
Weighted Average Grant Date Fair Value	'		'		'
PSU/RSU Vesting Increment	'		0.57		'
Cash Bonus Plan [Member]	'		'		'
Cash Bonus Plan	'		'		'
Percent of base compensation	200.00%		'		'
Accrued cash bonus plan expense	$41,800,000		$16,300,000		$23,900,000
[1]	The number of awards assumes a one multiplier. The final number of shares of common stock issued may vary depending on the ending three-year performance multiplier, which ranges from zero to two.

Compensation_Plans_Restricted_

Compensation Plans Restricted Stock Units Under the Equity Incentive Compensation Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation plans	'	'	'
Stock-based compensation expense	$32,347,000	$30,185,000	$26,824,000
Restricted Stock Units (RSUs) [Member]	'	'	'
Compensation plans	'	'	'
Stock-based compensation expense	13,100,000	9,800,000	5,300,000
Unrecognized stock based compensation expense	19,300,000	'	'
Fair value of PSUs/RSUs Granted in Period	19,800,000	18,800,000	7,200,000
RSUs	'	'	'
Non-vested at the beginning of the period (in shares)	496,244	308,877	333,359
Granted (in shares)	329,939	379,332	98,952
Vested (in shares)	-207,376	-166,672	-105,820
Forfeited (in shares)	-38,376	-25,293	-17,614
Non-vested at the end of the period (in shares)	580,431	496,244	308,877
Weighted- Average Grant-Date Fair Value	'	'	'
Non-vested outstanding at the beginning of the period (in dollars per share)	$51.81	$44.33	$31.16
Granted (in dollars per share)	$60.01	$49.47	$72.69
Vested (in dollars per share)	$49.73	$32.72	$30.61
Forfeited (in dollars per share)	$54.37	$51.06	$36.80
Non-vested outstanding at the end of the period (in dollars per share)	$57.05	$51.81	$44.33
RSU Vesting Increment	0.33	'	'
Fair value of PSUs/RSUs Vested in Period	$10,300,000	$5,400,000	$3,200,000
Shares issued in period	207,378	166,670	105,820
Stock issued for settlement, PSU, net of tax (in shares)	139,391	116,813	72,305
Shares held for settlement of income and payroll tax obligations (in shares)	67,987	49,857	33,515
First Anniversary [Member] | Restricted Stock Units (RSUs) [Member]	'	'	'
Weighted- Average Grant-Date Fair Value	'	'	'
RSU Vesting Increment	'	0.14	'
Second Anniversary [Member] | Restricted Stock Units (RSUs) [Member]	'	'	'
Weighted- Average Grant-Date Fair Value	'	'	'
RSU Vesting Increment	'	0.29	'
Third Anniversary [Member] | Restricted Stock Units (RSUs) [Member]	'	'	'
Weighted- Average Grant-Date Fair Value	'	'	'
RSU Vesting Increment	'	0.57	'

Compensation_Plans_Stock_Optio

Compensation Plans Stock Option Grants Under the Equity Incentive Compensation Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Aggregate Intrinsic Value	'		'	'
Excess tax benefit	$0		$0	$0
Cash received from exercise	3,200,000		3,000,000	5,000,000
Employee Stock Option [Member]	'		'	'
Shares	'		'	'
Outstanding, start of year	267,846		508,214	920,765
Exercised	-228,758		-240,368	-412,551
Forfeited	0		0	0
Outstanding, end of year	39,088		267,846	508,214
Vested and exercisable at end of year	39,088		267,846	508,214
Weighted Average Exercise Price	'		'	'
Outstanding, start of year (in dollars per share)	$14.95		$13.86	$13.11
Exercised (in dollars per share)	$13.92		$12.65	$12.19
Forfeited (in dollars per share)	$0		$0	$0
Outstanding, end of year (in dollars per share)	$20.87		$14.95	$13.86
Vested and exercisable at end of year (in dollars per share)	$20.87		$14.95	$13.86
Aggregate Intrinsic Value	'		'	'
Exercised	12,326,994		11,842,575	24,359,240
Outstanding	2,432,837		9,983,177	30,109,110
Vested and exercisable at end of year	$2,432,837		$9,983,177	$30,109,110
Exercise Price Range 1 [Member] | Employee Stock Option [Member]	'		'	'
Aggregate Intrinsic Value	'		'	'
Exercise Price	$20.87	[1]	'	'
Number of options outstanding and exercisable	39,088		'	'
Weighted average remaining contractual life	'1 year		'	'
[1]	Exercise price is equal to the weighted average exercise price.

Compensation_Plans_Employee_St

Compensation Plans Employee Stock Purchase Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation plans	'	'	'
Number of shares available for grant	3,800,000	'	'
Proceeds from sale of common stock	$6,858,000	$5,816,000	$7,327,000
Stock-based compensation expense	32,347,000	30,185,000	26,824,000
Employee Stock [Member]	'	'	'
Compensation plans	'	'	'
Maximum employee subscription rate	15.00%	'	'
Maximum employee subscription	25,000	'	'
Percent of offering date price paid	85.00%	'	'
Number of shares available for grant	1,200,000	'	'
Issuance of common stock under Employee Stock Purchase Plan (in shares)	77,427	66,485	41,358
Proceeds from sale of common stock	3,700,000	2,800,000	2,300,000
Risk free interest rate	0.10%	0.10%	0.20%
Dividend yield	0.20%	0.20%	0.20%
Volatility factor of the expected market price of the Company's common stock	41.10%	47.80%	36.30%
Expected life (in years)	'6 months	'6 months	'6 months
Stock-based compensation expense	$1,100,000	$948,000	$682,000

Compensation_Plans_401k_Plan_D

Compensation Plans 401(k) Plan (Details) (401 (k) Plan[Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
401 (k) Plan[Member]	'	'	'
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]	'	'	'
Maximum employee deferral percentage	60.00%	'	'
Employer match, maximum percentage	6.00%	'	'
Employer contribution	$4.20	$3.50	$2.90

Compensation_Plans_Net_Profits

Compensation Plans Net Profits Plan (Details) (Net Profits Plan [Member], USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net Profits Plan [Member]	'	'	'	'
Costs recovered for payment to employees from net profit plan	100.00%	'	'	'
Percentage of future net cash flow received by participants from net profit plan	10.00%	'	'	'
Percentage Of future net cash flow received by participants from net profit plan increased yo	20.00%	'	'	'
Additional payment employees from net profit plan	200.00%	'	'	'
General and administrative expense	$13,734,000	$15,565,000	'	$19,326,000
Exploration expense	1,310,000	1,751,000	'	2,091,000
Total	15,044,000	17,316,000	'	21,417,000
Amount of cash payments related to divested properties	$10,300,000	$2,300,000	$6,300,000	'

Pension_Benefits_Details

Pension Benefits (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]	'	'	'
Defined Benefit Plan, Benefit Obligation Beginning of Year	$40,237,000	$29,480,000	'
Defined Benefit Plan, Service Cost	6,291,000	4,934,000	3,800,000
Defined Benefit Plan, Interest Cost	1,627,000	1,374,000	1,184,000
Defined Benefit Plan, Amendments	0	0	'
Defined Benefit Plan, Actuarial Loss	-1,577,000	5,467,000	'
Defined Benefit Plan, Benefits Paid	-3,293,000	-1,018,000	'
Defined Benefit Plan, Benefit Obligation End of Year	43,285,000	40,237,000	29,480,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]	'	'	'
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	20,254,000	13,940,000	'
Defined Benefit Plan, Actual Return on Plan Assets	2,726,000	1,952,000	'
Defined Benefit Plan, Employer Contribution	4,971,000	5,380,000	5,300,000
Defined Benefit Plan, Benefits Paid, Qualified Pension Plan	-3,293,000	-1,018,000	-1,500,000
Defined Benefit Plan, Fair Value of Plan Assets End of Year	24,658,000	20,254,000	13,940,000
Defined Benefit Plan, Funded Status of Plan	-18,627,000	-19,983,000	'
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]	'	'	'
Defined Benefit Plan, Benefit Obligation End of Year	43,285,000	40,237,000	29,480,000
Defined Benefit Plan, Accumulated Benefit Obligation	32,396,000	29,437,000	'
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	-24,658,000	-20,254,000	-13,940,000
Defined Benefit Plan, Accumulated Unfunded Benefit Obligation	7,738,000	9,183,000	'
Pre-tax Amounts Recognized in Accumulated Other Comprehensive Income	'	'	'
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Gains (Losses), before Tax	8,439,000	12,427,000	'
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	136,000	153,000	'
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Transition Assets (Obligations), before Tax	0	0	'
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	8,575,000	12,580,000	'
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]	'	'	'
Defined Benefit Plan, Amounts Recognized In Other Comprehensive Income, Actuarial Losses, Before Tax	2,766,000	-4,680,000	-3,014,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Arising During Period, before Tax	0	0	-170,000
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Benefit Cost, before Tax	-17,000	-17,000	0
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net (Gain) Loss Recognized in Net Periodic Benefit Cost, Net of Tax	-1,222,000	-754,000	-405,000
Total Other Comprehensive Income (Loss)	4,005,000	-3,909,000	-2,779,000
Components of Net Periodic Benefit Costs for Both Pension Plans	'	'	'
Defined Benefit Plan, Service Cost	6,291,000	4,934,000	3,800,000
Defined Benefit Plan, Interest Cost	1,627,000	1,374,000	1,184,000
Defined Benefit Plan, Expected Return on Plan Assets	-1,538,000	-1,165,000	-880,000
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	17,000	17,000	0
Defined Benefit Plan, Amortization of Gains (Losses)	1,222,000	754,000	405,000
Defined Benefit Plan, Net Periodic Benefit Cost	7,619,000	5,914,000	4,509,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost [Abstract]	'	'	'
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	5.00%	3.90%	4.70%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	6.20%	6.20%	6.20%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.90%	4.70%	5.30%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	7.50%	7.50%	7.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	6.20%	6.20%	6.20%
Defined Benefit Plan, Assets, Target Allocations [Abstract]	'	'	'
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	100.00%	'	'
Defined Benefit Plan, Asset Allocation	100.00%	100.00%	'
Future Benefit Payments	'	'	'
Defined Benefit Plan, Expected Future Benefit Payments in Year One	2,120,000	'	'
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	2,837,000	'	'
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	3,287,000	'	'
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	3,993,000	'	'
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	4,407,000	'	'
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	33,031,000	'	'
Defined Benefit Plan, Percent Vested After Two Years of Service	40.00%	'	'
Defined Benefit Plan, Years of Service Required for Initial Vesting	2	'	'
Defined Benefit Plan, Annual Vesting Increment	20.00%	'	'
Pension And Other Post-retirement Benefit Plans, Gain (Loss) Amortization Threshold	10.00%	'	'
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year	436,000	'	'
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	4,300,000	'	'
Equity Securities [Member]	'	'	'
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]	'	'	'
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	8,660,000	'	'
Defined Benefit Plan, Fair Value of Plan Assets End of Year	10,744,000	'	'
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]	'	'	'
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	-10,744,000	'	'
Defined Benefit Plan, Assets, Target Allocations [Abstract]	'	'	'
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	44.00%	'	'
Defined Benefit Plan, Asset Allocation	43.60%	42.70%	'
Other than Securities Investment [Member]	'	'	'
Defined Benefit Plan, Assets, Target Allocations [Abstract]	'	'	'
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	23.00%	'	'
Defined Benefit Plan, Asset Allocation	24.20%	24.50%	'
Debt Securities [Member]	'	'	'
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]	'	'	'
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	6,630,000	'	'
Defined Benefit Plan, Fair Value of Plan Assets End of Year	7,937,000	'	'
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]	'	'	'
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	($7,937,000)	'	'
Defined Benefit Plan, Assets, Target Allocations [Abstract]	'	'	'
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	33.00%	'	'
Defined Benefit Plan, Asset Allocation	32.20%	32.80%	'

Pension_Benefits_Fair_Value_of

Pension Benefits Fair Value of Plan Assets in Heirarchy (Details) (USD $)

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In Thousands, unless otherwise specified

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

investment Purchases [Member]

investment Purchases [Member]

Investment Income [Member]

Investment Income [Member]

Unrealized Investment Gain [Member]

Cash And Money Market Funds [Member]

Cash And Money Market Funds [Member]

Cash And Money Market Funds [Member]

Cash And Money Market Funds [Member]

Cash And Money Market Funds [Member]

Cash And Money Market Funds [Member]

Cash And Money Market Funds [Member]

Cash And Money Market Funds [Member]

Domestic Equity Securities [Member]

Domestic Equity Securities [Member]

Domestic Equity Securities [Member]

Domestic Equity Securities [Member]

Domestic Equity Securities [Member]

Domestic Equity Securities [Member]

Domestic Equity Securities [Member]

Domestic Equity Securities [Member]

International Equity Securities [Member]

International Equity Securities [Member]

International Equity Securities [Member]

International Equity Securities [Member]

International Equity Securities [Member]

International Equity Securities [Member]

International Equity Securities [Member]

International Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

High-yield Bonds [Member]

High-yield Bonds [Member]

High-yield Bonds [Member]

High-yield Bonds [Member]

High-yield Bonds [Member]

High-yield Bonds [Member]

High-yield Bonds [Member]

High-yield Bonds [Member]

Fixed Income Funds [Member]

Fixed Income Funds [Member]

Fixed Income Funds [Member]

Fixed Income Funds [Member]

Fixed Income Funds [Member]

Fixed Income Funds [Member]

Fixed Income Funds [Member]

Fixed Income Funds [Member]

Floating Rate Corporate Debt [Member]

Floating Rate Corporate Debt [Member]

Floating Rate Corporate Debt [Member]

Floating Rate Corporate Debt [Member]

Floating Rate Corporate Debt [Member]

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Debt Securities [Member]

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Commodities Investment [Member]

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Commodities Investment [Member]

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Commodities Investment [Member]

Commodities Investment [Member]

Real Estate Investment [Member]

Real Estate Investment [Member]

Real Estate Investment [Member]

Real Estate Investment [Member]

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Real Estate Investment [Member]

Real Estate Investment [Member]

Real Estate Investment [Member]

Hedge Funds [Member]

Hedge Funds [Member]

Hedge Funds [Member]

Hedge Funds [Member]

Hedge Funds [Member]

Hedge Funds [Member]

Hedge Funds [Member]

Hedge Funds [Member]

Collective Investment Trust [Member]

Collective Investment Trust [Member]

Collective Investment Trust [Member]

Collective Investment Trust [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Fair Value, Inputs, Level 1 [Member]

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Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value

$3,421

$2,384

$0

'

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3

'

'

'

'

'

'

'

'

'

742

2,329

161

55

134

'

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'

Defined Benefit Plan, Fair Value of Plan Assets

$24,658

$20,254

$13,940

$18,098

$17,870

$3,139

$0

$3,421

$2,384

'

'

'

'

'

$0

$778

$0

$778

$0

$0

$0

$0

$7,371

[1]

$5,920

$4,888

[1]

$5,920

$2,483

[1]

$0

$0

[1]

$0

$3,373

[2]

$2,740

$3,373

[2]

$2,740

$0

[2]

$0

$0

[2]

$0

$10,744

$8,660

$8,261

$8,660

$2,483

$0

$0

$0

$1,448

[3]

$1,240

$1,448

[3]

$1,240

$0

[3]

$0

$0

[3]

$0

$5,006

[4]

$4,204

[4]

$5,006

[4]

$4,204

[4]

$0

[4]

$0

[4]

$0

[4]

$0

[4]

$1,483

[5]

$1,186

[5]

$1,483

[4]

$1,186

[5]

$0

[4]

$0

[5]

$0

[4]

$0

[5]

$7,937

$6,630

$7,937

$6,630

$0

$0

$0

$0

$945

[6]

$669

[6]

$945

[6]

$669

[6]

$0

[6]

$0

[6]

$0

[6]

$0

[6]

$859

[7]

$783

[7]

$0

[7]

$0

[7]

$0

[7]

$0

[7]

$859

[7]

$783

[7]

$3,517

[8]

$2,734

[8]

$955

[8]

$1,133

[8]

$0

[8]

$0

[8]

$2,562

[8]

$1,601

[8]

$656

[9]

$0

[9]

$656

[9]

$0

[9]

$5,977

$4,186

$1,900

$1,802

$656

$0

$3,421

$2,384

Defined Benefit Plan, Asset Allocation

100.00%

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

0.00%

3.80%

'

'

'

'

'

'

29.90%

[1]

29.20%

'

'

'

'

'

'

13.70%

[2]

13.50%

'

'

'

'

'

'

43.60%

42.70%

'

'

'

'

'

'

5.90%

[3]

6.10%

[3]

'

'

'

'

'

'

20.30%

[4]

20.80%

[4]

'

'

'

'

'

'

6.00%

[5]

5.90%

[5]

'

'

'

'

'

'

32.20%

32.80%

'

'

'

'

'

'

3.80%

[6]

3.30%

[6]

'

'

'

'

'

'

3.50%

[7]

3.90%

[7]

'

'

'

'

'

'

14.30%

[8]

13.50%

[8]

'

'

'

'

'

'

2.60%

[9]

'

'

'

'

20.70%

'

'

'

'

'

'

[1]

quity securities consist of United States large and small capitalization companies, which are actively traded securities that can be sold upon demand.

[2]

International equity securities consists of a well-diversified portfolio of holdings of mostly large issuers organized in developed countries with liquid markets, commingled with investments in equity securities of issuers located in emerging markets and believed to have strong sustainable financial productivity at attractive valuations.

[3]

High-yield bonds consist of non-investment grade fixed income securities. The investment objective is to obtain high current income. Due to the increased level of default risk, security selection focuses on credit-risk analysis.

[4]

The objective is to achieve value added from sector or issue selection by constructing a portfolio to approximate the investment results of the Barclay's Capital Aggregate Bond Index with a modest amount of variability in duration around the index.

[5]

Investments consist of floating rate bank loans. TheB interestB rates on theseB loans are typically reset on a periodic basis to account for changes in the level of interest rates.

[6]

Investments with exposure to commodity price movements, primarily through the use of futures, swaps and other commodity-linked securities.

[7]

The investment objective of direct real estate is to provide current income with the potential for long-term capital appreciation. Ownership in real estate entails a long-term time horizon, periodic valuations, and potentially low liquidity.

[8]

The hedge fund portfolio includes an investment in an actively traded global mutual fund that focuses on alternative investments and a hedge fund of funds that invests both long and short using a variety of investment strategies.

[9]

(9)Collective investment trusts invest in short-term investments and are valued at the net asset value of the collective investment trust. The net asset value, as provided by the trustee, is used as a practical expedient to estimate fair value. The net asset value is based on the fair value of the underlying investments held by the fund less its liabilities.

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Asset Retirement Obligations [Line Items]	'	'
Asset Retirement Obligations Assets Held-for-sale Noncurrent	$3,033,000	$1,393,000
Asset Retirement Obligation, Current	2,500,000	6,200,000
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'	'
Asset Retirement Obligation: Beginning of Year	120,518,000	95,906,000
Asset Retirement Obligation, Liabilities Incurred	18,682,000	13,050,000
Asset Retirement Obligation, Liabilities Settled	-33,129,000	-8,101,000
Asset Retirement Obligation, Accretion Expense	5,997,000	4,679,000
Asset Retirement Obligation, Revision of Estimate	9,118,000	14,984,000
Asset Retirement Obligation: End of Year	$121,186,000	$120,518,000
Minimum [Member]	'	'
Asset Retirement Obligations [Line Items]	'	'
Asset Retirement Obligations, Assumptions Used, Risk Free Interest Rate	5.50%	'
Maximum [Member]	'	'
Asset Retirement Obligations [Line Items]	'	'
Asset Retirement Obligations, Assumptions Used, Risk Free Interest Rate	12.00%	'

Derivative_Financial_Instrumen3

Derivative Financial Instruments (Details)

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Feb. 12, 2014

Crude Oil [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

NYMEX WTI [Member]

Argus LLS [Member]

IF El Paso Permian [Member]

IF HSC [Member]

IF NGPL TXOK [Member]

IF NNG Ventura [Member]

IF NNG Ventura [Member]

IF PEPL [Member]

IF Reliant N/S [Member]

IF NGPL MidCont [Member]

IF TETCO STX [Member]

OPIS IsoButane Mt Belv Non TET [Member]

OPIS Natural Gasoline Mt Belv Non TET [Member]

OPIS NButane Mt Belv Non TET [Member]

OPIS Propane Mt Belv TET [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Collar [Member]

Collar [Member]

First Quarter of 2014 [Member]

First Quarter of 2014 [Member]

First Quarter of 2014 [Member]

First Quarter of 2014 [Member]

First Quarter of 2014 [Member]

Second Quarter of 2014 [Member]

Second Quarter of 2014 [Member]

Second Quarter of 2014 [Member]

Second Quarter of 2014 [Member]

Second Quarter of 2014 [Member]

Third Quarter of 2014 [Member]

Third Quarter of 2014 [Member]

Third Quarter of 2014 [Member]

Third Quarter of 2014 [Member]

Fourth Quarter of 2014Member]

Fourth Quarter of 2014Member]

Fourth Quarter of 2014Member]

Fourth Quarter of 2014Member]

2015 [Member]

2015 [Member]

2015 [Member]

2015 [Member]

2016 [Member]

2016 [Member]

2017 [Member]

2018 [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

bbl

MMBTU

bbl

Crude Oil [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Crude Oil [Member]

Natural Gas [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Collar [Member]

Collar [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Collar [Member]

Collar [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Collar [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Collar [Member]

Swap [Member]

Swap [Member]

Collar [Member]

Collar [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Crude Oil [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

IF NNG Ventura [Member]

OPIS Natural Gasoline Mt Belv Non TET [Member]

OPIS Propane Mt Belv TET [Member]

IF CIG N System [Member]

Swap [Member]

Swap [Member]

First Quarter of 2014 [Member]

First Quarter of 2014 [Member]

Second Quarter of 2014 [Member]

Second Quarter of 2014 [Member]

Third Quarter of 2014 [Member]

Third Quarter of 2014 [Member]

Fourth Quarter of 2014Member]

Fourth Quarter of 2014Member]

2015 [Member]

2016 [Member]

bbl

MMBTU

bbl

bbl

MMBTU

Crude Oil [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Crude Oil [Member]

Natural Gas [Member]

Crude Oil [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Crude Oil [Member]

Natural Gas [Member]

Crude Oil [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Crude Oil [Member]

Crude Oil [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Crude Oil [Member]

Crude Oil [Member]

Natural Gas [Member]

Crude Oil [Member]

Natural Gas [Member]

Crude Oil [Member]

Natural Gas [Member]

Natural Gas [Member]

Natural Gas [Member]

bbl

MMBTU

bbl

Natural Gas [Member]

Natural Gas Liquids [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

Swap [Member]

bbl

MMBTU

bbl

bbl

MMBTU

bbl

MMBTU

bbl

bbl

MMBTU

bbl

MMBTU

bbl

bbl

bbl

MMBTU

bbl

bbl

bbl

MMBTU

bbl

MMBTU

bbl

MMBTU

MMBTU

MMBTU

MMBTU

bbl

Natural Gas [Member]

Natural Gas Liquids [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Natural Gas [Member]

Natural Gas [Member]

MMBTU

bbl

MMBTU

bbl

MMBTU

bbl

MMBTU

bbl

MMBTU

MMBTU

Derivative Financial Instruments

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Portion of future oil and NGL production included in derivative contracts

18,800,000

'

2,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12,452,000

'

2,549,000

6,387,000

'

2,600,000

'

913,000

694,000

'

2,373,000

'

565,000

431,000

'

973,000

'

544,000

973,000

891,000

'

527,000

923,000

2,911,000

'

3,366,000

'

2,704,000

'

'

'

17,500,000

'

4,000,000

'

'

'

'

'

1,797,000

'

516,000

'

531,000

'

416,000

'

334,000

'

'

Portion of Gas Production Covered Under Derivative Contract

'

265,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

245,704,000

'

'

20,214,000

'

33,651,000

'

'

1,540,000

'

25,729,000

'

'

4,194,000

'

26,398,000

'

'

'

23,965,000

'

'

'

63,317,000

'

14,480,000

'

39,014,000

23,430,000

10,200,000

'

237,900,000

'

'

'

'

'

2,490,000

'

261,000

'

365,000

'

341,000

'

321,000

'

1,133,000

69,000

Gas Derivative Contracts Settled Early

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

18,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted- Average Contract Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

96.92

4.25

59.72

'

'

94.95

3.96

63.22

'

'

95.25

4.01

62.34

'

95.16

4.01

61.57

'

89.06

4.03

'

'

85.19

4.18

4.21

4.31

'

'

'

'

'

'

'

'

'

4.39

54.85

3.84

52.53

3.89

52.47

3.97

52.52

3.72

4.12

Index percent of oil fixed swap

'

'

'

97.00%

3.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted- Average Floor Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

80.97

4.39

'

'

'

85

4.38

'

'

'

85

'

'

'

85

'

'

85

3.96

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted- Average Ceiling Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

115.07

5.58

'

'

'

102.5

5.29

'

'

'

102.58

'

'

'

102.63

'

'

94.25

4.3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Index percent of natural gas fixed swaps

'

'

'

'

'

3.00%

77.00%

3.00%

'

2.00%

6.00%

8.00%

1.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

30.00%

'

'

70.00%

'

'

'

'

'

'

'

'

'

'

'

'

Index percent of natural gas collars

'

'

'

'

'

2.00%

57.00%

3.00%

5.00%

'

7.00%

14.00%

'

12.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Index percent of NGL fixed swaps

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.00%

34.00%

3.00%

61.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

17.00%

83.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative_Financial_Instrumen4

Derivative Financial Instruments Fair Value (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Fair value of derivative assets and liabilities	'	'
Price Risk Derivatives, at Fair Value, Net	$21,500,000	$38,700,000
Derivative Assets, Current	21,559,000	37,873,000
Derivative Liabilities, Current	26,380,000	8,999,000
Derivative Assets, Noncurrent	30,951,000	16,466,000
Derivative Liabilities, Noncurrent	4,640,000	6,645,000
Derivative Asset, Fair Value, Amount Offset Against Collateral	52,510,000	54,339,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	-30,652,000	-13,400,000
Derivative Asset, Fair Value, Amount Offset Against Collateral, Net	21,858,000	40,939,000
Derivative Liability, Fair Value, Amount Offset Against Collateral	-31,020,000	-15,644,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	30,652,000	13,400,000
Derivative Liability, Fair Value, Amount Offset Against Collateral, Net	-368,000	-2,244,000
Not Designated as Hedging Instrument [Member]	'	'
Fair value of derivative assets and liabilities	'	'
Derivative Assets, Current	21,559,000	37,873,000
Derivative Liabilities, Current	26,380,000	8,999,000
Derivative Assets, Noncurrent	30,951,000	16,466,000
Derivative Liabilities, Noncurrent	4,640,000	6,645,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member]	'	'
Fair value of derivative assets and liabilities	'	'
Fair Value: Derivative Assets	52,510,000	54,339,000
Fair Value: Derivative Liabilities	$31,020,000	$15,644,000

Derivative_Financial_Instrumen5

Derivative Financial Instruments Gains and Losses (Details) (USD $)

12 Months Ended

In Thousands, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2010

Crude oil

Crude oil

Crude oil

Natural Gas [Member]

Natural Gas [Member]

Natural Gas [Member]

Natural Gas Liquids [Member]

Natural Gas Liquids [Member]

Natural Gas Liquids [Member]

Convertible Debt [Member]

Convertible Debt [Member]

Convertible Debt [Member]

Derivative, (Gain) Loss on Derivative, Net [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative cash settlement (gain) loss:

($22,062)

[1]

($44,264)

[1]

$25,671

[1]

$15,161

$11,893

$22,633

($30,338)

($47,270)

($10,711)

($6,885)

($8,887)

$13,749

'

'

'

Derivative (gain) loss

-3,080

-55,630

-37,086

-496

-31,981

-3,391

16,285

31,777

-64,310

3,193

-11,162

4,944

'

'

'

Total derivative gain (2)

-3,080

[2]

-55,630

[2]

-37,086

[2]

'

'

'

'

'

'

'

'

'

'

'

'

Amount reclassified from AOCIL

1,115

-2,264

12,997

'

'

'

'

'

'

'

'

'

'

'

'

Gain (Loss) on Hedging Activity

($1,777)

$3,866

($20,707)

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Interest Rate, Stated Percentage

'

'

'

'

'

'

'

'

'

'

'

'

3.50%

3.50%

3.50%

[1]

Total derivative cash settlement gain (loss) is reported in the derivative cash settlement gain (loss) line item on the consolidated statements of cash flows within net cash provided by operating activities.

[2]

Total derivative gain is reported in the derivative gain line item on the consolidated statements of cash flows within net cash provided by operating activities.

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2011

Dec. 31, 2013

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Fair Value, Measurements, Nonrecurring [Member]

Fair Value, Measurements, Nonrecurring [Member]

Fair Value, Measurements, Nonrecurring [Member]

Fair Value, Measurements, Nonrecurring [Member]

Fair Value, Measurements, Nonrecurring [Member]

Fair Value, Measurements, Nonrecurring [Member]

Net Profit Plan liability [Member]

Net Profit Plan liability [Member]

Level 1

Level 1

Level 1

Level 1

Level 2

Level 2

Level 2

Level 2

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Level 1

Level 1

Level 2

Level 2

Fair Value, Inputs, Level 3 [Member]

Fair Value, Inputs, Level 3 [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Financial assets and liabilities measured at fair value on a recurring basis

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percent Decrease in Discount Rate for Sensitivity Analysis

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.00%

Payment to Settle, Net Profit Plan Liability

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$2,600,000

'

Assets:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivatives

'

'

'

'

0

[1]

0

[1]

'

'

52,510,000

[1]

54,339,000

[1]

'

'

0

[1]

0

[1]

'

'

'

'

'

'

'

'

Derivative Asset, Fair Value, Amount Offset Against Collateral

52,510,000

54,339,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proved oil and gas properties

5,637,462,000

5,401,684,000

'

'

'

'

'

'

'

'

'

'

'

'

0

[2]

0

[2]

0

[2]

0

[2]

62,178,000

[2]

209,959,000

[2]

'

'

Unproved Oil and Gas Property, Successful Efforts Method, Fair Value

271,100,000

175,287,000

'

'

'

'

'

'

'

'

'

'

'

'

0

[2]

0

[2]

0

[2]

0

[2]

3,280,000

[2]

42,765,000

[2]

'

'

Oil and gas properties held for sale, net of accumulated depletion, depreciation and amortization of $7,390 in 2013 and $20,676 in 2012

19,072,000

33,620,000

'

'

'

'

'

'

'

'

'

'

'

'

0

[2]

'

0

[2]

'

650,000

[2]

'

'

'

Liabilities [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Liability, Fair Value, Gross Liability

'

'

'

'

0

[1]

0

[1]

'

'

31,020,000

[1]

15,644,000

[1]

'

'

0

[1]

0

[1]

'

'

'

'

'

'

'

'

Net Profits Plan liability

$56,985,000

$78,827,000

$0

[1]

$0

[1]

'

'

$0

[1]

$0

[1]

'

'

$56,985,000

[1]

$78,827,000

[1]

'

'

'

'

'

'

'

'

'

'

[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 that is measured at fair value on a nonrecurring basis.

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
		A
Proved Oil and Gas Properties	'	'		'		'
Discount rate used for fair value of oil and gas properties (as a percent)	'	12.00%		'		'
Net Profit Plan liability [Member]	'	'		'		'
Liability measured at fair value using Level 3 inputs	'	'		'		'
Discount rate to calculate liability pools currently in payout (as a percent)	'	12.00%		'		'
Number of periods used for price assumptions of strip prices of liabilities	'	5		'		'
Period used for price assumptions of strip prices of liabilities (in years)	'	1		'		'
Percentage change in commodity prices (as a percent)	'	5.00%		'		'
Change in liability due to change in commodity prices by 5 percent	'	$5,000,000		'		'
Percentage increase in discount rate (as a percent)	'	1.00%		'		'
Increase in liability due to a 1 percent decrease in discount rate	'	2,000,000		'		'
Decrease in liability due to a 1 percent increase in discount rate	'	2,000,000		'		'
Liability measured at fair value using Level 3 inputs	'	'		'		'
Net Profits Plan Liability: Beginning Balance	135,850,000	78,827,000		107,731,000		135,850,000
Net increase (decrease) in liability	'	3,527,000	[1]	-9,251,000	[1]	2,269,000	[1]
Net settlements	'	-25,369,000	[1],[2],[3]	-19,653,000	[1],[2],[3]	-30,388,000	[1],[2],[3]
Transfers in (out) of Level 3	'	0		0		0
Net Profits Plan Liability: Ending balance	'	56,985,000		78,827,000		107,731,000
Amount paid for settlement of liabilities	2,600,000	'		'		'
Net Profits Plan [Member]	'	'		'		'
Liability measured at fair value using Level 3 inputs	'	'		'		'
Amount of cash payments related to divested properties	'	10,300,000		2,300,000		6,300,000
6.625% Senior Notes Due 2019 [Member]	'	'		'		'
Liability measured at fair value using Level 3 inputs	'	'		'		'
Long-term Debt, Fair Value	'	374,290,000		371,875,000		'
6.50% Senior Notes Due 2021 [Member]	'	'		'		'
Liability measured at fair value using Level 3 inputs	'	'		'		'
Long-term Debt, Fair Value	'	373,625,000		371,070,000		'
6.50% Senior Notes Due 2023 [Member]	'	'		'		'
Liability measured at fair value using Level 3 inputs	'	'		'		'
Long-term Debt, Fair Value	'	422,000,000		424,200,000		'
5% Senior Notes Due 2024 [Member]	'	'		'		'
Liability measured at fair value using Level 3 inputs	'	'		'		'
Long-term Debt, Fair Value	'	$475,315,000	[4]	$0	[4]	'
[1]	Net changes in the Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item of the accompanying statements of operations.
[2]	During 2011, the Company elected to cash out several Net Profits Plan pools with a $2.6 million direct payment. As a result, the Company reduced its Net Profits Plan liability by that amount. There was no impact on the accompanying statements of operations for the period ended DecemberB 31, 2011, related to these settlements.
[3]	Settlements represent cash payments made or accrued under the Net Profits Plan. The amounts in the table include cash payments made or accrued under the Net Profits Plan of $10.3 million, $2.3 million, and $6.3 million relating to divestiture proceeds for the years ended DecemberB 31, 2013, 2012, and 2011, respectively.
[4]	(1) The 2024 Notes were issued on May 20, 2013.

Acquisition_and_Development_Ag1

Acquisition and Development Agreement and Carry and Earning Agreement (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Jun. 30, 2011
			Mitsui E&P Texas LP	Mitsui E&P Texas LP
Acquisition and Development Agreement [Abstract]	'	'	'	'
Percentage of working interests transferred to acquiree entity (as a percent)	'	'	'	12.50%
Acreage of working interests transferred to acquiree entity (in acres)	'	'	'	39,000
Percentage of the entity's costs and expenses during the first three years following the closing of the transaction, borne by the acquiree entity (as a percent)	'	'	90.00%	'
Costs and expenses incurred by acquiree entity on behalf of entity that the acquiree entity has agreed to pay	'	'	'	$680,000,000
Portion of Drilling and Completion Costs Not Carried by Acquirer	'	'	10.00%	'
Restricted cash	96,713,000	86,773,000	94,959,000	'
Carry Amount, Portion Used to Date	'	'	$573,800,000	'

Suspended_Well_Costs_Details

Suspended Well Costs (Details) (USD $)	3 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]	'	'	'	'
Capitalized Exploratory Well Costs that Have Been Capitalized for Period of One Year or Less	'	$34,527	$9,100	$15,618
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	'	0	0	2,982
Capitalized Exploratory Well Costs	'	34,527	9,100	18,600
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]	'	'	'	'
Capitalized Exploratory Well Costs Beginning Balance	'	9,100	18,600	35,862
Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves	'	34,527	9,100	15,618
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves	'	-9,100	-5,865	-32,880
Capitalized Exploratory Well Cost, Charged to Expense	3,600	0	-12,735	0
Capitalized Exploratory Well Costs Ending Balance	'	$34,527	$9,100	$18,600
Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects	'	0	0	2