SM Energy (SM) 10-K25 Feb 152014 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information Document (USD $)	12 Months Ended
Document and Entity Information Document (USD $)	Dec. 31, 2014	Feb. 18, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	SM Energy Co
Entity Central Index Key	893538
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Amendment Flag	FALSE
Common Stock, Shares, Outstanding		67,463,060
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$5,564,325,288

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$120	$282,248
Accounts receivable (Note 2)	322,630	318,371
Derivative asset	402,668	21,559
Deferred income taxes	0	10,749
Prepaid expenses and other	19,625	14,574
Total current assets	745,043	647,501
Proved oil and gas properties	7,348,436	5,637,462
Less - accumulated depletion, depreciation, and amortization	-3,233,012	-2,583,698
Unproved oil and gas properties	532,498	271,100
Wells in progress	503,734	279,654
Oil and gas properties held for sale, net of accumulated depletion, depreciation and amortization of $22,482 and $7,390, respectively	17,891	19,072
Other property and equipment, net of accumulated depreciation of $37,079 and $28,775, respectively	334,356	236,202
Total property and equipment, net	5,503,903	3,859,792
Derivative asset	189,540	30,951
Restricted cash	0	96,713
Other noncurrent assets	78,214	70,208
Total other noncurrent assets	267,754	197,872
Total Assets	6,516,700	4,705,165
LIABILITIES
Accounts payable and accrued expenses (note 2)	640,684	606,751
Derivative liability	0	26,380
Deferred tax liability	142,976	0
Other current liabilities	1,000	6,000
Total current liabilities	784,660	639,131
Revolving credit facility	166,000	0
Senior Notes (note 5)	2,200,000	1,600,000
Asset retirement obligation	120,867	118,692
Net Profits Plan liability	27,136	56,985
Deferred income taxes; Net, non-current	891,681	650,125
Derivative liability	70	4,640
Other noncurrent liabilities	39,631	28,771
Total noncurrent liabilities	3,445,385	2,459,213
Commitments and contingencies (note 6)
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued: 67,463,060 and 67,078,853 shares outstanding, respectively; net of treasury shares: 67,463,060 and 67,056,441, respectively	675	671
Additional paid-in capital	283,295	257,720
Treasury stock, at cost: zero and 22,412, respectively	0	-823
Retained earnings	2,013,997	1,354,669
Accumulated other comprehensive loss	-11,312	-5,416
Total stockholders' equity	2,286,655	1,606,821
Total Liabilities and Stockholders' Equity	$6,516,700	$4,705,165

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS Parenthetical (USD $)	Dec. 31, 2014	Dec. 31, 2013
Common Stock, Shares, Outstanding	67,463,060	67,056,441
Treasury Stock, Shares	0	22,412
Common Stock, Shares, Issued	67,463,060	67,078,853
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Par Value Per Share	$0.01	$0.01
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$3,233,012,000	$2,583,698,000
Assets Held-for-sale [Member]
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	22,482,000	7,390,000
Other Capitalized Property Plant and Equipment [Member]
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization	$37,079,000	$28,775,000

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Operating revenues:
Oil, gas, and NGL production revenue	$2,481,544		$2,199,550		$1,473,868
Gain (loss) on divestiture activity	646		27,974		-27,018
Marketed gas system revenue	24,897		60,039		52,808
Other operating revenues	15,220		5,811		5,444
Total operating revenues and other income	2,522,307		2,293,374		1,505,102
Operating Expenses
Oil, gas, and NGL production expense	715,878		597,045		391,872
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	767,532		822,872		727,877
Exploration	129,857		74,104		90,248
Impairment of proved properties	84,480		172,641		208,923
Abandonment and impairment of unproved properties	75,638		46,105		16,342
General and administrative	167,103		149,551		119,815
Change in Net Profits Plan liability	-29,849		-21,842		-28,904
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	583,264	[1]	3,080	[1]	55,630	[1]
Marketed gas system expense	24,460		57,647		47,583
Other operating expenses	4,658		30,076		6,993
Total operating expenses	1,356,493		1,925,119		1,525,119
Income (loss) from operations	1,165,814		368,255		-20,017
Nonoperating income (expense):
Other, net	-2,561		67		220
Interest expense	-98,554		-89,711		-63,720
Income (loss) before income taxes	1,064,699		278,611		-83,517
Income tax (expense) benefit	-398,648		-107,676		29,268
Net income (loss)	$666,051		$170,935		($54,249)
Basic weighted-average common shares outstanding	67,230		66,615		65,138
Diluted weighted-average common shares outstanding	68,044		67,998		65,138
Earnings Per Share, Basic [Abstract]
Basic net income (loss) per common share	$9.91		$2.57		($0.83)
Earnings Per Share, Diluted [Abstract]
Diluted net income (loss) per common share	$9.79		$2.51		($0.83)

[1]	(2)B Total derivative gain is reported in the derivative gain line item on the accompanying 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
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income (loss)	$666,051		$170,935		($54,249)
Reclassification to earnings	0		1,115		-2,264
Pension liability adjustment	-5,896	[1]	2,483	[1]	-2,470	[1]
Total other comprehensive income (loss), net of tax	-5,896		3,598		-4,734
Total comprehensive income (loss)	$660,155		$174,533		($58,983)

[1]	(2)B Refer to Note 1 - Summary of Significant Accounting Policies for detail of the pension amount reclassified to general and administrative expense on the Companybs consolidated statements of operations.

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	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
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	29,862	323
Stock Issued During Period, Value, Stock Options Exercised			3,038
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures				30,486
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 (shares)		864,106
Stock-based compensation expense	30,185
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	31,949	398
Stock Issued During Period, Value, Stock Options Exercised			3,183
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures				28,169
Issuance of common stock upon stock option exercises (in shares)		228,758
Stock-based compensation expense	32,347
Other income tax benefit (expense)	-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
Common Stock, Dividends, Per Share, Declared	$0.10
Increase (Decrease) in Stockholders' Equity
Net income (loss)	666,051				666,051
Other comprehensive income (loss)	-5,896					-5,896
Cash dividends, $ 0.10 per share	-6,723				-6,723
Issuance of common stock under Employee Stock Purchase Plan	4,061	1	4,060
Issuance of common stock under Employee Stock Purchase Plan (in shares)		83,136
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings	-10,624	3	-10,627
Issuance of common stock upon vesting of RSUs and settlement of PSUs, net of shares used for tax withholdings (in shares)		256,718
Issuance of common stock upon stock option exercises	816	0	31,871	823
Stock Issued During Period, Value, Stock Options Exercised		0	816
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		5,265		22,412
Issuance of common stock upon stock option exercises (in shares)		39,088
Stock-based compensation expense	32,694
Other income tax benefit (expense)	545		545
Balances at Dec. 31, 2014	$2,286,655	$675	$283,295	$0	$2,013,997	($11,312)
Balances (in shares) at Dec. 31, 2014		-67,463,060		0

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cash flows from operating activities:
Net income (loss)	$666,051		$170,935		($54,249)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Gain (Loss) on Disposition of Oil and Gas Property	646		27,974		-27,018
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	767,532		822,872		727,877
Exploratory dry hole expense	44,427		5,846		20,861
Impairment of proved properties	84,480		172,641		208,923
Abandonment and impairment of unproved properties	75,638		46,105		16,342
Share-based Compensation	32,694		32,347		30,185
Change in Net Profits Plan liability	-29,849		-21,842		-28,904
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	583,264	[1]	3,080	[1]	55,630	[1]
Derivative cash settlements	-28,419		22,062		44,264
Amortization of debt discount and deferred financing costs	6,146		5,390		6,769
Deferred income taxes	397,780		105,555		-29,638
Plugging and abandonment	-8,796		-9,946		-2,856
Other	1,069		2,775		527
Changes in current assets and liabilities:
Accounts receivable	24,088		-78,494		-21,389
Prepaid expenses and other	-1,822		98		733
Accounts payable and accrued expenses	9,466		93,224		31,136
Net cash provided by operating activities	1,456,575		1,338,514		921,969
Cash flows from investing activities:
Net proceeds from sale of oil and gas properties	43,858		424,849		55,375
Capital expenditures	-1,974,798		-1,553,536		-1,507,828
Acquisition of proved and unproved oil and gas properties	-544,553		-61,603		-5,773
Other	-3,256		-2,613		893
Net cash used in investing activities	-2,478,749		-1,192,903		-1,457,333
Cash flows from financing activities:
Proceeds from credit facility	1,285,500		1,203,000		1,609,000
Repayment of credit facility	-1,119,500		-1,543,000		-1,269,000
Debt issuance costs related to credit facility	-3,388		-3,444		0
Net proceeds from Senior Notes	589,991		490,185		392,138
Repayment of 3.50% Senior Convertible Notes	0		0		-287,500
Proceeds from sale of common stock	4,877		6,858		5,816
Dividends paid	-6,723		-6,663		-6,511
Net share settlement from issuance of stock awards	-10,624		-16,220		-21,622
Other	-87		-5		-225
Net cash provided by financing activities	740,046		130,711		422,096
Net change in cash and cash equivalents	-282,128		276,322		-113,268
Cash and cash equivalents at beginning of period	282,248		5,926		119,194
Cash and cash equivalents at end of period	120		282,248		5,926
Supplemental schedule of additional cash flow information and noncash investing and financing activities:
Interest Paid, Net	89,145		70,702		51,328
Net cash refunded for income taxes	$1,936		($204)		($1,389)

[1]	(2)B Total derivative gain is reported in the derivative gain line item on the accompanying statements of cash flows within net cash provided by operating activities.

CONSOLIDATED_STATEMENTS_OF_CAS1

CONSOLIDATED STATEMENTS OF CASH FLOWS Parenthetical (USD $)	3 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Sep. 30, 2013
Supplemental Cash Flow Elements [Abstract]
Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed)	$6.20	$25

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
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 Company is an independent energy company engaged in the acquisition, exploration, development, and production of crude oil and condensate, natural gas, and NGLs in onshore North America.

	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, 2014, through the filing date of this report.
	Certain prior period amounts have been reclassified to conform to the current period presentation on the accompanying financial statements. The Company’s refundable income taxes are combined and presented in the prepaid expenses and other financial statement line item within the accompanying balance sheets. The Company’s land and materials inventory are combined and presented in the other property and equipment, net of accumulated depreciation financial statement line item within the accompanying balance sheets. Lastly, the asset retirement obligation associated with oil and gas properties held for sale is no longer separately presented and is presented in the asset retirement obligation financial statement line item within the accompanying balance sheets. Within the accompanying consolidated statements of operations (“accompanying statements of operations”), the Company’s realized hedge gain (loss) is combined and presented in the other operating revenues financial statement line item. In the accompanying consolidated statements of cash flows (“accompanying statements of cash flows”) in cash flows from operating activities, refundable income taxes is now combined and presented with prepaid expenses and other. Additionally, receipts from restricted cash related to any like-kind exchanges under Section 1031 of the Internal Revenue Code are now combined and presented in the other, net financial statement line item within net cash used in investing activities on the accompanying statements of cash flows.
	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 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 has no restricted cash at December 31, 2014. The restricted cash balance at December 31, 2013, mainly consisted of cash payments that were 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 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, 2014 and 2013, 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. The Company does not believe the loss of any single purchaser would materially impact its operating results, as crude oil, natural gas, and NGLs are products with well-established markets and numerous purchasers in the Company’s operating regions. During 2014, the Company had one major customer, which accounted for approximately 19 percent of total production revenue, which is discussed in the next paragraph. In 2014, the Company also sold to four entities that are under common ownership. In aggregate, these four entities accounted for approximately 14 percent of total production revenues in 2014, however, none of these entities individually accounted for greater than 10 percent of total production revenue. During 2013, the Company had three major customers, which accounted for approximately 26 percent, 16 percent, and 12 percent, respectively, of total production revenue. During 2012, the Company had two major customers, which accounted for approximately 21 percent and 13 percent, respectively, of total production revenue.

	During the third quarter of 2013, the Company entered into various marketing agreements with a joint venture partner, whereby the Company is subject to certain gathering, transportation, and processing through-put commitments for up to 10 years pursuant to each contract. While the Company’s joint venture partner is the first purchaser under these contracts, accounting for 19 percent of total production revenue in 2014, the Company also shares with them the risk of non-performance by their counterparty purchasers. Several of the Company’s joint venture partner’s counterparty purchasers under these contracts are also direct purchasers of products produced by the Company.

	The Company’s policy is to use the commodity affiliates of the lenders under its credit facility as its derivative counterparties. Additionally, the Company’s policy is that the counterparty must have investment grade senior unsecured debt ratings. Each of the Company’s nine counterparties currently meet both of these requirements.
	The Company has accounts in the following locations with a national bank: Denver, Colorado; Houston, Texas; Midland, Texas; and Billings, Montana. 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. G&G 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, 2014, and 2013, the estimated salvage value of the Company’s equipment was $50.8 million and $57.5 million, respectively.
	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. For additional discussion on assets held for sale, please refer to Note 3 – Acquisitions, 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 30 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.
	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, 2014, and 2013, the Company has capitalized approximately $35.0 million and $11.2 million, respectively, 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 prices, its NGL derivative contracts to OPIS prices, and its gas derivative contracts to various regional index prices associated with pipelines into which the Company’s gas production is sold. 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 to be 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 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.
	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 proved developed 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 $84.5 million, $172.6 million, and $208.9 million, of proved property impairment expense for the years ended December 31, 2014, 2013, and 2012, respectively. The impairments of proved properties in 2014 were a result of the significant decline in commodity prices in late 2014 and recognition of the outcomes of exploration and delineation wells in certain prospects in the Company’s South Texas & Gulf Coast and Permian regions. 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.
	For the years ended December 31, 2014, 2013, and 2012, the Company recorded expense related to the abandonment and impairment of unproved properties of $75.6 million, $46.1 million, and $16.3 million, respectively. The Company’s abandonment and impairment of unproved properties expense in 2014 was due to acreage the Company no longer intended to develop as a result of exploration and delineation activities and the recent decline in commodity prices. The Company’s abandonment and impairment of unproved properties expense in 2013 was mostly related to acreage the Company no longer intended to develop in its Permian region. The Company’s abandonment and impairment of unproved properties expense 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 property 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 – Acquisitions, Divestitures, and Assets Held for Sale.
	Stock-Based Compensation

	At December 31, 2014, the Company had stock-based employee compensation plans that included RSUs, PSUs, and restricted stock awards 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 remain 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. The Company recorded a loss from continuing operations for the year ended December 31, 2012, and therefore, the shares into which the 3.50% Senior Convertible Notes were convertible were anti-dilutive and excluded from the calculation of diluted earnings per share, as shown in the table below.
	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,
	2014			2013			2012
	(in thousands)
Dilutive	814			1,383			—

Anti-dilutive	—			—			2,102

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


	For the Years Ended December 31,
	2014				2013			2012
	(in thousands, except per share amounts)
Net income (loss)	$	666,051			$	170,935		$	(54,249	)

Basic weighted-average common shares outstanding	67,230				66,615			65,138

Add: dilutive effect of stock options, unvested RSUs, and contingent PSUs	814				1,383			—

Add: dilutive effect of 3.50% Senior Convertible Notes (1)	—				—			—

Diluted weighted-average common shares outstanding	68,044				67,998			65,138

Basic net income (loss) per common share	$	9.91			$	2.57		$	(0.83	)

Diluted net income (loss) per common share	$	9.79			$	2.51		$	(0.83	)

____________________________________________
(1) For the year ended December 31, 2012, the shares into which the 3.50% Senior Convertible Notes were convertible were anti-dilutive and excluded from the calculation of diluted earnings per share.

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 Adjustments				Pension Liability Adjustments
	(in thousands)
For the year ended December 31, 2012
Net actuarial loss					$	(4,680	)
Reclassification to earnings	$	(3,865	)		771

Tax benefit	1,601				1,439

Loss, net of tax	$	(2,264	)		$	(2,470	)
For the year ended December 31, 2013
Net actuarial gain					$	2,766

Reclassification to earnings	$	1,777			1,239

Tax expense	(662		)		(1,522		)
Income, net of tax	$	1,115			$	2,483

For the year ended December 31, 2014
Net actuarial loss					$	(10,062	)
Reclassification to earnings	$	—			706

Tax benefit	—				3,460

Loss, net of tax	$	—			$	(5,896	)

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 $166.0 million of outstanding loans under its credit facility as of December 31, 2014. The Company had no borrowings outstanding under its credit facility as of December 31, 2013. 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 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 (“SPE”), which would have been established for the purpose of facilitating off-balance sheet arrangements or other contractually narrow or limited purposes.
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. The Company has not been involved in any unconsolidated SPE transactions in 2014 or 2013.
Recently Issued Accounting Standards
Effective October 1, 2014, the Company early adopted, on a prospective basis, Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2014-08, “Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity.” This ASU changed the criteria for reporting discontinued operations while enhancing disclosures in this area. There was no impact to the Company’s financial statements or disclosures from the early adoption of this standard.

In May 2014, the FASB issued new authoritative accounting guidance related to the recognition of revenue from contracts with customers. This guidance is to be applied using a retrospective method or a modified retrospective method, as outlined in the guidance, and is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2016. Early application is not permitted. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company’s financial statements and disclosures.

In August 2014, the FASB issued new authoritative guidance that requires management to evaluate whether there are conditions or events that raise substantial doubt about an entity’s ability to continue as a going concern within one year after the date that the entity’s financial statements are issued, or within one year after the date the entity’s financial statements are available to be issued, and to provide disclosures when certain criteria are met. This guidance is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early application is permitted. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company’s financial statements and disclosures but does not believe it will impact the Company's financial statements or disclosures.

In January 2015, the FASB issued new authoritative accounting guidance that simplifies income statement presentation by eliminating extraordinary items from GAAP. This guidance is to be applied either prospectively or retrospectively and is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2015. Early application is permitted provided the guidance is applied from the beginning of the annual year of adoption. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company’s financial statements and disclosures.

In February 2015, the FASB issued new authoritative accounting guidance meant to clarify the consolidation reporting guidance in GAAP. This guidance is to be applied using a retrospective method or a modified retrospective method, as outlined in the guidance, and is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2015. Early application is permitted. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company’s financial statements and disclosures.
There are no other accounting standards applicable to the Company that have been issued but not yet adopted by the Company as of December 31, 2014, and through the filing date of this report.

Accounts_Receivable_and_Accoun

Accounts Receivable and Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2014
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,
		2014		2013

		(in thousands)
	Accrued oil, gas, and NGL production revenue	$	180,250	$	228,169

	Amounts due from joint interest owners	58,347		37,517

	Accrued derivative settlements	39,811		770

	State severance tax refunds	24,394		29,213

	Other	19,828		22,702

	Total accounts receivable	$	322,630	$	318,371

	Accounts payable and accrued expenses are comprised of the following:


		As of December 31,
		2014		2013
		(in thousands)
	Accrued capital expenditures	$	357,156	$	217,820

	Revenue and severance tax payable	63,779		87,852

	Accrued lease operating expense	34,822		29,296

	Accrued property taxes	15,059		10,401

	Joint owner advances	152		96,636

	Accrued compensation	56,279		71,466

	Accrued interest	40,786		40,027

	Other	72,651		53,253

	Total accounts payable and accrued expenses	$	640,684	$	606,751

Divestitures_and_Assets_Held_f

Divestitures and Assets Held for Sale	12 Months Ended
	Dec. 31, 2014
Divestitures and Assets Held for Sale Disclosure [Abstract]
Divestitures and Assets Held for Sale	Note 3 – Acquisitions, Divestitures, and Assets Held for Sale
	2014 Acquisition Activity


	•	Gooseneck Property Acquisitions. On September 24, 2014, the Company acquired approximately 61,000 net acres of proved and unproved oil and gas properties in its Gooseneck area in North Dakota, along with related equipment, contracts, records, and other assets. Total cash consideration paid by the Company was $325.2 million and the effective date for the acquisition was July 1, 2014.

	On October 15, 2014, the Company acquired additional interests in proved and unproved oil and gas properties in its Gooseneck area. Total cash consideration paid by the Company was $84.8 million and the effective date for the acquisition was August 1, 2014.

	It was determined that both of these acquisitions met the criteria of a business combination under Accounting Standards Codification (“ASC”) Topic 805, Business Combinations. The Company allocated the preliminary adjusted purchase price to the acquired assets and liabilities based on fair value as of the respective acquisition dates, as summarized in the table below. These acquisitions are subject to normal post-closing adjustments, which are expected to be completed in the first half of 2015. Refer to Note 11 – Fair Value Measurements for additional discussion on the valuation techniques used in determining the fair value of acquired properties.


		As of September 24, 2014			As of October 15, 2014
	Purchase Price	(in thousands)
	Cash consideration	$	325,230		$	84,836


	Fair value of assets acquired:
	Proved oil and gas properties	$	203,493		$	54,360

	Unproved oil and gas properties	126,622			29,469

	Total fair value of oil and gas properties acquired	330,115			83,829


	Working capital	(2,772		)	2,625

	Asset retirement obligation	(2,113		)	(1,618		)
	Total fair value of net assets acquired	$	325,230		$	84,836



	•	Rocky Mountain Acquisitions. In addition to the Gooseneck property acquisitions discussed above, the Company acquired other proved and unproved properties in its Rocky Mountain region during 2014 in multiple transactions for approximately $134.5 million in total cash consideration, plus approximately 7,000 net acres of non-core assets in the Company’s Rocky Mountain region. These acquisitions are subject to normal post-closing adjustments, which are expected to be completed in early 2015.

	2014 Divestiture Activity


	•	Rocky Mountain Divestiture. During the second quarter of 2014, the Company divested certain non-core assets in the Montana portion of the Williston Basin. Total divestiture proceeds were $50.1 million and the final gain on this divestiture was $26.9 million.

	The Company recorded $27.6 million of write-downs to fair value less estimated costs to sell for assets that were held for sale during the year ended December 31, 2014, which are reflected as a loss on divestiture activity in the accompanying statements of operations, and mostly offset the gain on the Rocky Mountain divestiture discussed above. Please refer to Assets Held for Sale below for further discussion.

	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 divestiture proceeds were $368.5 million and the net gain on these divestitures was $25.3 million. A portion of one transaction was structured to qualify as a like-kind exchange under Section 1031 of the IRC.


	•	Rocky Mountain Divestitures. During 2013, the Company divested of certain non-strategic assets located in its Rocky Mountain region. Final divestiture proceeds for these divestitures were $57.1 million and the final net gain was $13.2 million.


	•	Permian Divestiture. In December 2013, the Company divested of certain non-strategic assets located in its Permian region. Final proceeds for this divestiture were $14.0 million and the final net loss was $7.0 million.

	The Company recorded an immaterial write-down to fair value less estimated costs to sell for assets that were held for sale as of December 31, 2013.
	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 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.

	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, 2014, the accompanying balance sheets present $17.9 million of assets held for sale, net of accumulated DD&A expense. There is a corresponding asset retirement obligation liability of $438,000 for assets held for sale included in the asset retirement obligation financial statement line item. Assets held for sale are recorded at the lesser of their respective carrying value or fair value less estimated costs to sell. Certain assets classified as held for sale during 2014 were written down to fair value less estimated costs to sell, which was recorded in the gain (loss) on divestiture activity line item in the accompanying statements of operations.

Subsequent to December 31, 2014, the Company began marketing its assets in the Arkoma Basin of Oklahoma and in the Arklatex area of east Texas and northern Louisiana and expects the assets to be sold during 2015. These assets did not meet the requirements to be classified as held for sale as of December 31, 2014.

The Company determined that neither these planned nor executed asset sales qualify for discontinued operations accounting under financial statement presentation authoritative guidance.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
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,
			2014				2013				2012
			(in thousands)
	Current portion of income tax expense
	Federal		$	—			$	—			$	—

	State		868				2,121				370

	Deferred portion of income tax expense (benefit)		397,780				105,555				(29,638		)

	Total income tax expense (benefit)		$	398,648			$	107,676			$	(29,268	)

	Effective tax rate		37.4		%		38.6		%		35		%

	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 2014, 2013, or 2012.
	The components of the net deferred income tax liabilities are as follows:


			As of December 31,
			2014				2013
			(in thousands)
	Deferred tax liabilities:
	Oil and gas properties		$	1,029,424			$	768,463

	Derivative asset		220,437				9,529

	Other		4,475				1,245

	Total deferred tax liabilities		1,254,336				779,237

	Deferred tax assets:

	Federal and state tax net operating loss carryovers		184,447				91,788

	Stock compensation		16,763				18,820

	Other long-term liabilities		16,301				13,341

	Net Profits Plan liability		9,414				20,913

	Total deferred tax assets		226,925				144,862

	Valuation allowance		(7,246		)		(5,001		)
	Net deferred tax assets		219,679				139,861

	Total net deferred tax liabilities		1,034,657				639,376

	Less: current deferred income tax liabilities		(152,082		)		(172		)
	Add: current deferred income tax assets		9,106				10,921

	Non-current net deferred tax liabilities		$	891,681			$	650,125

	Current federal income tax refundable		$	4,734			$	4,630

	Current state income tax refundable		$	—			$	—

	Current state income tax payable		$	25			$	1,460

	At December 31, 2014, the Company estimated its federal net operating loss carryforward at $626.2 million, which includes unrecognized excess income tax benefits associated with stock awards of $126.7 million. The federal net operating loss carryforward begins to expire in 2031. The Company has estimated state net operating loss carryforwards of $284.8 million that expire between 2015 and 2035 and it has federal R&D credit carryforwards of $3.5 million that expire between 2028 and 2032. The Company’s valuation allowance relates to charitable contribution carryforwards, state net operating loss carryforwards, and state tax credits, which the Company anticipates will expire before they can be utilized. The change in the valuation allowance from 2013 to 2014 primarily reflects a change in the Company’s position regarding anticipated utilization of cumulative state net operating losses.
	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,
	2014				2013				2012
	(in thousands)
Federal statutory tax expense (benefit)	$	372,644			$	97,514			$	(29,231	)

Increase (decrease) in tax resulting from:
State tax expense (benefit) (net of federal benefit)	21,350				9,400				(992		)

Research and development credit	—				—				(970		)

Change in valuation allowance	2,245				(314		)		1,524

Other	2,409				1,076				401

Income tax expense (benefit)	$	398,648			$	107,676			$	(29,268	)

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 state income tax expense (benefit) reported in the current year. 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 or estimated state revenue occurs during the year.
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. The Internal Revenue Service (“IRS”) initiated an audit in the first quarter of 2012 related to an R&D tax credit 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 an R&D tax credit claimed for open tax years during the audit period. During the third quarter ended September 30, 2014, the Company successfully reached an agreement with the IRS Appeals Office (“Appeals”) related to the claimed R&D credit and recorded an immaterial adjustment. In the fourth quarter of 2014, Appeals returned the case to the Examination Team for final review. At December 31, 2014, the Company was waiting on final review and evaluating the basis for claiming the R&D credit for the 2012 and 2013 tax years. Subsequent to year-end, the Company concluded its evaluation, and preliminary estimates indicate it may be entitled to claim approximately $2.4 million of additional net R&D credit. The Company anticipates finalizing the amounts and filing amended returns in the first quarter of 2015. The tables above do not include the impact of the estimated amount.
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, 2014.
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. At December 31, 2014, the Company estimates the range of reasonably possible change in 2015 to the table below could be from zero to $1.2 million.
The total amount recorded for unrecognized tax benefits is presented below:


	For the Years Ended December 31,
	2014				2013				2012
	(in thousands)
Beginning balance	$	2,358			$	2,278			$	1,961

Additions for tax positions of prior years	140				80				317

Settlements	(916		)		—				—

Ending balance	$	1,582			$	2,358			$	2,278

LongTerm_Debt

Long-Term Debt	12 Months Ended
Long-Term Debt	Dec. 31, 2014
Debt Disclosure [Abstract]
Long-Term Debt	Note 5 – Long-term Debt
	Revolving Credit Facility
	The Company and its lenders entered into a Second Amendment to the Fifth Amended and Restated Credit Agreement on December 10, 2014. The Company incurred approximately $3.4 million in deferred financing costs associated with the amendment and extension of this credit facility. As amended, the Company’s credit facility has a maximum loan amount of $2.5 billion, current aggregate lender commitments of $1.5 billion, and a maturity date of December 10, 2019. The borrowing base is subject to regular semi-annual redeterminations. On October 6, 2014, the lending group redetermined the Company's borrowing base under the credit facility and increased it from $2.2 billion to $2.4 billion. The December 10, 2014 amendment to the credit facility specified that the borrowing base was not reduced by the issuance of the 2022 Notes and will remain at $2.4 billion until the next redetermination date, scheduled for April 1, 2015. The borrowing base redetermination process under the credit facility considers the value of the Company’s proved oil and gas properties, as determined by the lender group. Borrowings under the facility are secured by at least 75 percent of the value 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 adjusted EBITDAX, as defined by the Company’s credit agreement as the ratio of debt to 12-month trailing adjusted EBITDAX, of less than 4.0 and an adjusted current ratio, as defined by the Company’s 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, 2014, 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		1.25	%	1.5	%	1.75	%		2	%	2.25	%
	ABR Loans or Swingline Loans		0.25	%	0.5	%	0.75	%		1	%	1.25	%
	Commitment Fee Rate		0.3	%	0.3	%	0.35	%		0.375	%	0.375	%

	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 18, 2015, December 31, 2014, and December 31, 2013:



		As of February 18, 2015			As of December 31, 2014			As of December 31, 2013
		(in thousands)
	Credit facility balance	$	341,000		$	166,000		$	—
	Credit facility balance	$	341,000		$	166,000		$	—
	Letters of credit (1)	$	808		$	808		$	808
	Letters of credit (1)	$	808		$	808		$	808
	Available borrowing capacity	$	1,158,192		$	1,333,192		$	1,299,192
	Available borrowing capacity	$	1,158,192		$	1,333,192		$	1,299,192
	____________________________________________
	(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, 2014, and 2013, consisted of the following:


		As of December 31,
		2014			2013
		(in thousands)
	2019 Notes	$	350,000		$	350,000
	2019 Notes	$	350,000		$	350,000
	2021 Notes	350,000			350,000
	2021 Notes	350,000			350,000
	2022 Notes	600,000			—
	2022 Notes	600,000			—
	2023 Notes	400,000			400,000
	2023 Notes	400,000			400,000
	2024 Notes	500,000			500,000
	2024 Notes	500,000			500,000
	Total Senior Notes	$	2,200,000		$	1,600,000
	Total Senior Notes	$	2,200,000		$	1,600,000

	The Senior Notes are unsecured senior obligations and rank equal in right of payment with all of the Company’s existing and any future unsecured senior debt, and are senior in right of payment to any future subordinated debt. There are no subsidiary guarantors of the Senior Notes. The Company is subject to certain covenants under the 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, 2014, and through the filing date of this report.
	2022 Notes
	On November 17, 2014, the Company issued $600.0 million in aggregate principal amount of 6.125% Senior Notes due 2022. The 2022 Notes were issued at par and mature on November 15, 2022. The Company received net proceeds of $590.0 million after deducting fees of $10.0 million, which are being amortized as deferred financing costs over the life of the 2022 Notes. The net proceeds were used to repay outstanding borrowings under the Company’s credit facility and for general corporate purposes.
	Prior to November 15, 2017, the Company may redeem, on one or more occasions, up to 35 percent of the aggregate principal amount of the 2022 Notes with the net cash proceeds of certain equity offerings at a redemption price of 106.125% of the principal amount thereof, plus accrued and unpaid interest. The Company may also redeem the 2022 Notes, in whole or in part, at any time prior to November 15, 2018, at a redemption price equal to 100 percent of the principal amount of the 2022 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date.

	On or after November 15, 2018, the Company may also redeem all or, from time to time, a portion of the 2022 Notes at the redemption prices set forth below, during the twelve-month period beginning on November 15 of each applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:



	2018	103.063	%
	2019	101.531	%
	2020 and thereafter	100	%

	Additionally, on November 17, 2014, the Company entered into a registration rights agreement that provides holders of the 2022 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 2022 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 2022 Notes in lieu of a registered exchange offer. If the registration statement related to the exchange offer is not declared effective on or before November 17, 2015, 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 2022 Notes in an amount not to exceed one percent of the principal amount of the 2022 Notes until the exchange offer is completed or the shelf registration statement is declared effective.
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. The Company closed its offer to exchange its 2024 Notes for notes registered under the Securities Act on June 25, 2014.
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.

The Company may redeem the 2021 Notes, in whole or in part, at any time prior to November 15, 2016, at a redemption price equal to 100 percent 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 all or, from time to time, a portion of the 2019 Notes on or after February 15, 2015, at the prices set forth in the table 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, 2014, 2013, and 2012, were $16.2 million, $11.0 million, and $12.1 million, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
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 $116.1 million, gathering, processing, and transportation through-put commitments of $939.4 million, office leases, including maintenance, of $69.3 million, and other miscellaneous contracts and leases of $11.7 million. The annual minimum payments for the next five years and total minimum payments thereafter are presented below:


	Years Ending December 31,	(in thousands)
	2015	$	224,897

	2016	147,896

	2017	118,320

	2018	128,866

	2019	132,920

	Thereafter	383,619

	Total	$	1,136,518


	Drilling rig contracts

	The Company has multiple long-term drilling rig contracts. Early termination of these rig contracts as of December 31, 2014, would result in termination penalties of $75.8 million, which would be in lieu of paying the remaining drilling commitments of $116.1 million included in the table above.

	Transportation commitments

	The Company has gathering, processing, and transportation through-put commitments with various third parties that require delivery of a minimum amount of 1,411 Bcf of natural gas and 48 MMBbl of crude oil. These contracts expire at various dates through 2028 and the total amount of the commitment is approximately $939.4 million. The Company will be required to make periodic deficiency payments for any shortfalls in delivering the minimum volume commitments. If a shortfall in the minimum volume commitment for natural gas is projected, the Company has rights under certain contracts to arrange for third party gas to be delivered, and such volumes would count toward its minimum volume commitment. As of the filing date of this report, the Company does not expect to incur any material shortfalls.

	Office leases

	The Company leases office space under various operating leases with terms extending as far as 2026. Rent expense for years ended December 31, 2014, 2013, and 2012, was $6.5 million, $5.7 million, and $5.4 million, respectively. The Company also leases office equipment under various operating leases.

	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.

Compensation_Plans

Compensation Plans	12 Months Ended
	Dec. 31, 2014
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. 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 $37.8 million, $41.8 million, and $16.3 million of cash bonus expense related to the specific performance years ended December 31, 2014, 2013, and 2012, 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, 2014, 3.6 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 periods 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 $16.0 million, $16.8 million, and $18.2 million for the years ended December 31, 2014, 2013, and 2012, respectively. As of December 31, 2014, there was $19.8 million of total unrecognized expense related to PSUs, which is being amortized through 2017.
	A summary of the status and activity of non-vested PSUs is presented in the following table:


		For the Years Ended December 31,
		2014							2013				2012
		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)	572,469			$	66.07			669,308		$	63.91	885,894		$	57.52

	Granted (1)	202,404			$	94.66			274,831		$	64.13	314,853		$	51.98

	Vested (1)	(206,830	)		$	64.79			(345,005	)	$	60.06	(493,679	)	$	44.72

	Forfeited (1)	(134,383	)		$	86.72			(26,665	)	$	69.74	(37,760	)	$	65.35

	Non-vested at end of year(1)	433,660			$	73.63			572,469		$	66.07	669,308		$	63.91

	____________________________________________

	-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 2014, 2013, and 2012 was $19.2 million, $17.6 million, and $16.4 million for the 2014, 2013, and 2012 grants, respectively. The PSUs granted in 2013 and 2014 will remain unvested until the third anniversary date of their issuance, at which time they will fully vest. The PSUs granted in 2012 vest 1/3 on each of the first three anniversary dates of their issuance.
	The total fair value of PSUs that vested during the years ended December 31, 2014, 2013, and 2012 was $13.4 million, $20.7 million, and $22.1 million, respectively.
	During the year ended December 31, 2014, the Company settled PSUs that were granted in 2011, which earned a 0.55-times multiplier, by issuing a net 85,121 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, 45,042 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those PSUs for 2014.
	During the year ended December 31, 2013, the Company settled PSUs that were granted in 2010, which 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.
	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 periods of the award.
	The total expense associated with RSUs for the years ended December 31, 2014, 2013, and 2012, was $13.9 million, $13.1 million, and $9.8 million, respectively. As of December 31, 2014, there was $22.5 million of total unrecognized expense related to unvested RSU awards, which is being amortized through 2017. 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 before grant.
	A summary of the status and activity of non-vested RSUs is presented below:


		For the Years Ended December 31,
		2014							2013				2012
		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	580,431			$	57.05			496,244		$	51.81	308,877		$	44.33

	Granted	234,560			$	83.98			329,939		$	60.01	379,332		$	49.47

	Vested	(253,031	)		$	58.19			(207,376	)	$	49.73	(166,672	)	$	32.72

	Forfeited	(46,236	)		$	62.06			(38,376	)	$	54.37	(25,293	)	$	51.06

	Non-vested at end of year	515,724			$	68.29			580,431		$	57.05	496,244		$	51.81

	The fair value of RSUs granted in 2014, 2013, and 2012 was $19.7 million, $19.8 million, and $18.8 million, respectively. The RSUs granted in 2014, 2013, and 2012 vest 1/3 on each of the first three anniversary dates of the awards.
	The total fair value of RSUs that vested during the years ended December 31, 2014, 2013, and 2012, was $14.7 million, $10.3 million, and $5.4 million, respectively.
	During the years ended December 31, 2014, 2013, and 2012, the Company settled 253,031, 207,378, and 166,670 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 171,597, 139,391, and 116,813 for 2014, 2013, and 2012, respectively. The remaining 81,434, 67,987, and 49,857 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon the delivery of the shares underlying those RSUs for 2014, 2013, and 2012, respectively.

	Stock Option Grants Under the Equity Incentive Compensation Plan
	The Company 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 were exercisable for a period of up to 10 years from the date of grant. The remaining options from the 2004 grant were exercised during the year ended December 31, 2014. As of December 31, 2014, 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, 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

For the year ended December 31, 2014
Outstanding, start of year	39,088			$	20.87

Exercised	(39,088	)		$	20.87			$	1,993,726

Forfeited	—			$	—

Outstanding, end of year	—			$	—			$	—

Vested and exercisable at end of year	—			$	—			$	—

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, 2014, 2013, and 2012. Cash received from exercises under all share-based payment arrangements for the years ended December 31, 2014, 2013, and 2012, was $4.0 million, $3.2 million, and $3.0 million, respectively.
Director Shares
In 2014, 2013, and 2012, the Company issued 27,677, 28,169, and 30,486 shares, respectively, of the Company’s common stock to its non-employee directors pursuant to the Company’s Equity Plan. The Company recorded compensation expense related to these issuances of $1.6 million, $1.4 million, and $1.3 million for the years ended December 31, 2014, 2013, and 2012, respectively.
All shares of common stock issued to the Company’s non-employee directors are earned over the one-year service period following the date of grant, unless five years of service has been provided by the director, in which case that director’s shares vest immediately.
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 1.1 million shares available under the ESPP for issuance as of December 31, 2014. Shares issued under the ESPP totaled 83,136 in 2014, 77,427 in 2013, and 66,485 in 2012. Total proceeds to the Company for the issuance of these shares were $4.1 million, $3.7 million, and $2.8 million for the years ended December 31, 2014, 2013, and 2012, respectively.
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,
	2014			2013			2012
Risk free interest rate	0.1	%		0.1	%		0.1	%
Dividend yield	0.1	%		0.2	%		0.2	%
Volatility factor of the expected market	33	%		41.1	%		47.8	%
price of the Company’s common stock
Expected life (in years)	0.5			0.5			0.5

The Company expensed $1.1 million, $1.1 million, and $948,000 for the years ended December 31, 2014, 2013, and 2012, 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 also matches 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 $6.4 million, $4.2 million, and $3.5 million for the years ended December 31, 2014, 2013, and 2012, respectively. No discretionary contributions were made by the Company to the 401(k) Plan for any of these years.
Non-qualified Deferred Compensation Plan
In January 2014, the Company established a non-qualified deferred compensation (“NQDC”) plan intended to provide plan participants with the ability to plan for income tax events and the opportunity to receive a benefit for matching contributions in excess of IRC limits applicable to the Company’s 401(k) plan. The NQDC plan is designed to allow employee participants to defer a portion of base salary and cash bonuses paid pursuant to the Company’s cash bonus plan and director participants to defer a portion of the cash retainer paid to directors. Each year, participating employees may elect to defer (i) between 0% and 50% of their base salary and (ii) between 0% and 100% of the cash bonus paid pursuant to the cash bonus plan, and participating directors may elect to defer between 0% and 100% of their cash retainer. The NQDC plan requires the Company to make contributions for each eligible employee equal to 100% of the deferred amount for such employee, limited to 6% of such employee’s base salary and cash bonus. Each eligible employee’s interest in contributions made by the Company will vest 40% after the second year of such employee’s service to the Company, and 20% per year thereafter. A participant’s account will be distributed based upon the participant’s payment election made at the time of deferral. A participant may elect to have distributions made in lump sum or in annual installments ranging for a period from 1 to 10 years. Participants in the NQDC plan are currently limited to the Company’s officers and directors.
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,
	2014				2013				2012
	(in thousands)
General and administrative expense	$	8,326			$	13,734			$	15,565

Exploration expense	690				1,310				1,751

Total	$	9,016			$	15,044			$	17,316

Additionally, the Company made or accrued cash payments under the Net Profits Plan of $8.3 million, $10.3 million, and $2.3 million for the years ended December 31, 2014, 2013, and 2012, 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
Pension Benefits	Dec. 31, 2014
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 the 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,
		2014				2013
		(in thousands)
	Change in benefit obligation:
	Projected benefit obligation at beginning of year	$	43,285			$	40,237
	Projected benefit obligation at beginning of year	$	43,285			$	40,237
	Service cost	6,335				6,291
	Service cost	6,335				6,291
	Interest cost	2,191				1,627
	Interest cost	2,191				1,627
	Plan amendments	—				—
	Plan amendments	—				—
	Actuarial (gain) loss	8,821				(1,577		)
	Actuarial (gain) loss	8,821				(1,577		)
	Benefits paid	(2,765		)		(3,293		)
	Projected benefit obligation at end of year	57,867				43,285
	Projected benefit obligation at end of year	57,867				43,285

	Change in plan assets:
	Fair value of plan assets at beginning of year	24,658				20,254
	Fair value of plan assets at beginning of year	24,658				20,254
	Actual return on plan assets	737				2,726
	Actual return on plan assets	737				2,726
	Employer contribution	5,310				4,971
	Employer contribution	5,310				4,971
	Benefits paid	(2,765		)		(3,293		)
	Fair value of plan assets at end of year	27,940				24,658
	Fair value of plan assets at end of year	27,940				24,658
	Funded status at end of year	$	(29,927	)		$	(18,627	)

	The Company’s underfunded status for the Pension Plans for the years ended December 31, 2014 and 2013, is $29.9 million and $18.6 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, 2014. There are no plan assets in the Nonqualified Pension Plan.
	Accumulated Benefit Obligation in Excess of Plan Assets for the Pension Plans


		As of December 31,
		2014				2013
		(in thousands)
	Projected benefit obligation	$	57,867			$	43,285
	Projected benefit obligation	$	57,867			$	43,285

	Accumulated benefit obligation	$	43,205			$	32,396
	Accumulated benefit obligation	$	43,205			$	32,396
	Less: Fair value of plan assets	(27,940		)		(24,658		)
	Underfunded accumulated benefit obligation	$	15,265			$	7,738
	Underfunded accumulated benefit obligation	$	15,265			$	7,738
	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, 2014 and 2013, consist of:


		As of December 31,
		2014				2013
		(in thousands)
	Unrecognized actuarial losses	$	17,812			$	8,439
	Unrecognized actuarial losses	$	17,812			$	8,439
	Unrecognized prior service costs	118				136
	Unrecognized prior service costs	118				136
	Unrecognized transition obligation	—				—
	Unrecognized transition obligation	—				—
Accumulated other comprehensive loss	$	17,930			$	8,575
Accumulated other comprehensive loss	$	17,930			$	8,575
The estimated net loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost over the next fiscal year is $1.2 million.
Pre-tax changes recognized in other comprehensive income (loss) during 2014, 2013, and 2012, were as follows:


	For the Years Ended December 31,
	2014				2013				2012
	(in thousands)
Net actuarial gain (loss)	$	(10,062	)		$	2,766			$	(4,680	)
Net actuarial gain (loss)	$	(10,062	)		$	2,766			$	(4,680	)
Prior service cost	—				—				—
Prior service cost	—				—				—
Less: Amortization of:
Prior service cost	(17		)		(17		)		(17		)
Actuarial loss	(689		)		(1,222		)		(754		)
Total other comprehensive income (loss)	$	(9,356	)		$	4,005			$	(3,909	)
Total other comprehensive income (loss)	$	(9,356	)		$	4,005			$	(3,909	)
Components of Net Periodic Benefit Cost for the Pension Plans


	For the Years Ended December 31,
	2014				2013				2012
	(in thousands)
Components of net periodic benefit cost:
Service cost	$	6,335			$	6,291			$	4,934
Service cost	$	6,335			$	6,291			$	4,934
Interest cost	2,191				1,627				1,374
Interest cost	2,191				1,627				1,374
Expected return on plan assets that reduces periodic pension cost	(1,978		)		(1,538		)		(1,165		)
Amortization of prior service cost	17				17				17
Amortization of prior service cost	17				17				17
Amortization of net actuarial loss	689				1,222				754
Amortization of net actuarial loss	689				1,222				754
Net periodic benefit cost	$	7,254			$	7,619			$	5,914
Net periodic benefit cost	$	7,254			$	7,619			$	5,914
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,
	2014		2013		2012
Projected benefit obligation
Discount rate	4.30%		5.00%		3.90%
Rate of compensation increase	6.20%		6.20%		6.20%
Net periodic benefit cost
Discount rate	5.00%		3.90%		4.70%
Expected return on plan assets (1)	7.50%		7.50%		7.50%
Rate of compensation increase	6.20%		6.20%		6.20%
____________________________________________

-1	There is no assumed expected return on plan assets for the Nonqualified Pension Plan because there are no plan assets in the Nonqualified Pension Plan.
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		2015			2014			2013
Equity securities		42	%		39.6	%		43.6	%
Fixed income securities		35	%		33.9	%		32.2	%
Other securities		23	%		26.5	%		24.2	%
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 2014 and 2013. 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 values of the Company’s Qualified Pension Plan assets as of December 31, 2014 and 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
	Actual Asset Allocation			Total				Level 1 Inputs				Level 2 Inputs		Level 3 Inputs
				(in thousands)
31-Dec-14
Cash	—	%		$	—			$	—			$	—	$	—
Cash	—	%		$	—			$	—			$	—	$	—
Equity Securities
Equity Securities
Domestic (1)	27.1	%		7,569				5,550				2,019		—
Domestic (1)	27.1	%		7,569				5,550				2,019		—
International (2)	12.5	%		3,498				3,498				—		—
International (2)	12.5	%		3,498				3,498				—		—
Total Equity Securities	39.6	%		11,067				9,048				2,019		—
Total Equity Securities	39.6	%		11,067				9,048				2,019		—
Fixed Income Securities
Fixed Income Securities
High-Yield Bonds (3)	2.9	%		797				797				—		—
High-Yield Bonds (3)	2.9	%		797				797				—		—
Core Fixed Income (4)	22.4	%		6,247				6,247				—		—
Core Fixed Income (4)	22.4	%		6,247				6,247				—		—
Floating Rate Corp Loans (5)	8.6	%		2,413				2,413				—		—
Floating Rate Corp Loans (5)	8.6	%		2,413				2,413				—		—
Total Fixed Income Securities	33.9	%		9,457				9,457				—		—
Total Fixed Income Securities	33.9	%		9,457				9,457				—		—
Other Securities:
Other Securities:
Commodities (6)	2.9	%		810				810				—		—
Commodities (6)	2.9	%		810				810				—		—
Real Estate (7)	4.7	%		1,327				—				—		1,327
Real Estate (7)	4.7	%		1,327				—				—		1,327
Hedge Fund (8)	14.8	%		4,130				593				—		3,537
Hedge Fund (8)	14.8	%		4,130				593				—		3,537
Collective Investment Trusts (9)	4.1	%		1,149				—				1,149		—
Collective Investment Trusts (9)	4.1	%		1,149				—				1,149		—
Total Other Securities	26.5	%		7,416				1,403				1,149		4,864
Total Other Securities	26.5	%		7,416				1,403				1,149		4,864
Total Investments	100	%		$	27,940			$	19,908			$	3,168	$	4,864
Total Investments	100	%		$	27,940			$	19,908			$	3,168	$	4,864

31-Dec-13
Cash and Money Market Funds	—	%		$	—			$	—			$	—	$	—
Cash and Money Market Funds	—	%		$	—			$	—			$	—	$	—
Equity Securities
Domestic (1)	29.9	%		7,371				4,888				2,483		—
Domestic (1)	29.9	%		7,371				4,888				2,483		—
International (2)	13.7	%		3,373				3,373				—		—
International (2)	13.7	%		3,373				3,373				—		—
Total Equity Securities	43.6	%		10,744				8,261				2,483		—
Total Equity Securities	43.6	%		10,744				8,261				2,483		—
Fixed Income Securities
High-Yield Bonds (3)	5.9	%		1,448				1,448				—		—
High-Yield Bonds (3)	5.9	%		1,448				1,448				—		—
Core Fixed Income (4)	20.3	%		5,006				5,006				—		—
Core Fixed Income (4)	20.3	%		5,006				5,006				—		—
Floating Rate Corp Loans (5)	6	%		1,483				1,483				—		—
Floating Rate Corp Loans (5)	6	%		1,483				1,483				—		—
Total Fixed Income Securities	32.2	%		7,937				7,937				—		—
Total Fixed Income Securities	32.2	%		7,937				7,937				—		—
Other Securities:
Commodities (6)	3.8	%		945				945				—		—
Commodities (6)	3.8	%		945				945				—		—
Real Estate (7)	3.5	%		859				—				—		859
Real Estate (7)	3.5	%		859				—				—		859
Hedge Fund (8)	14.3	%		3,517				955				—		2,562
Hedge Fund (8)	14.3	%		3,517				955				—		2,562
Collective Investment Trusts (9)	2.6	%		656				—				656		—
Collective Investment Trusts (9)	2.6	%		656				—				656		—
Total Other Securities	24.2	%		5,977				1,900				656		3,421
Total Other Securities	24.2	%		5,977				1,900				656		3,421
Total Investments	100	%		$	24,658			$	18,098			$	3,139	$	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):


Balance at January 1, 2013	$	2,384
Balance at January 1, 2013	$	2,384
Purchases	742
Purchases	742
Realized gain on assets	161
Realized gain on assets	161
Unrealized gain on assets	134
Unrealized gain on assets	134
Balance at December 31, 2013	$	3,421
Balance at December 31, 2013	$	3,421
Purchases	1,232
Purchases	1,232
Realized gain on assets	144
Realized gain on assets	144
Unrealized gain on assets	67
Unrealized gain on assets	67
Balance at December 31, 2014	$	4,864
Balance at December 31, 2014	$	4,864
Contributions
The Company contributed $5.3 million, $5.0 million, and $5.4 million, to the Pension Plans in the years ended December 31, 2014, 2013, and 2012, respectively. The Company is expected to make a $5.8 million contribution to the Pension Plans in 2015.
Benefit Payments
The Pension Plans made actual benefit payments of $2.8 million, $3.3 million, and $1.0 million in the years ended December 31, 2014, 2013, and 2012, respectively. Expected benefit payments over the next 10 years are as follows:


Years Ending December 31,		(in thousands)
2015		$	3,006
2015		$	3,006
2016		$	3,046
2016		$	3,046
2017		$	3,921
2017		$	3,921
2018		$	4,558
2018		$	4,558
2019		$	5,204
2019		$	5,204
2020 through 2024		$	38,427
2020 through 2024		$	38,427

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2014
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 plugging and abandonment of its oil and gas properties. A liability for the fair value of an asset retirement obligation (“ARO”) 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 plugging and abandoning wells, estimated economic lives, estimated plugging and abandonment cost, 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 plugging and abandonment liabilities range from 5.5 percent to 12 percent. In periods subsequent to initial measurement of the liability, the Company must recognize period-to-period changes in the liability resulting from the passage of time, revisions to either the amount of the original estimate of undiscounted cash flows or changes in inflation factors and changes to the Company’s credit-adjusted risk-free rate as market conditions warrant.
	A reconciliation of the Company’s total asset retirement obligation liability is as follows:


		As of December 31,
		2014			2013
		(in thousands)
	Beginning asset retirement obligation	$	121,186		$	120,518

	Liabilities incurred	13,506			18,682

	Liabilities settled	(11,372		)	(33,129		)
	Accretion expense	6,090			5,997

	Revision to estimated cash flows	(7,286		)	9,118

	Ending asset retirement obligation	$	122,124		$	121,186

	As of December 31, 2014 and 2013, accounts payable and accrued expenses contain $1.3 million and $2.5 million, respectively, related to the Company’s current asset retirement obligation liability for estimated plugging and abandonment costs associated with a platform structure that is being retired, which is also included in the table above.

Derivative_Financial_Instrumen

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Note 10 – Derivative Financial Instruments
	Summary of Oil, Gas, and NGL Derivative Contracts in Place
	The Company has entered into various commodity derivative contracts to mitigate a portion of the exposure to potentially adverse market changes in commodity prices and the associated impact on cash flows. All contracts are entered into for other-than-trading purposes. The Company’s derivative contracts in place include swap and collar arrangements for oil, gas, and NGLs.
	As of December 31, 2014, the Company had commodity derivative contracts outstanding through the fourth quarter of 2019 for a total of 14.7 million Bbls of oil production, 230.8 million MMBtu of gas production, and 781,000 Bbls of NGL production.
	In a typical commodity swap agreement, if the agreed upon published third-party index price is lower than the swap fixed price, the Company receives the difference between the index price and the agreed upon swap fixed price. If the index price is higher than the swap fixed price, the Company pays the difference. For collar agreements, the Company receives the difference between an agreed upon index and the floor price if the index price is below the floor price. The Company pays the difference between the agreed upon ceiling price and the index price if the index price is above the ceiling price. No amounts are paid or received if the index price is between the floor and ceiling prices.
	The following tables summarize the approximate volumes and average contract prices of contracts the Company had in place as of December 31, 2014:
	Oil Contracts
	Oil Swaps


	Contract Period		NYMEX WTI Volumes			Weighted-
						Average
						Contract
						Price
			(Bbls)			(per Bbl)
	First quarter 2015		1,711,000			$	91.96

	Second quarter 2015		1,639,000			$	91.26

	Third quarter 2015		1,254,000			$	90.78

	Fourth quarter 2015		1,137,000			$	90.15

	2016		5,570,000			$	88.01

	All oil swaps		11,311,000


	Oil Collars


	Contract Period		NYMEX WTI			Weighted-				Weighted-
			Volumes			Average				Average
						Floor				Ceiling
						Price				Price
			(Bbls)			(per Bbl)				(per Bbl)
	First quarter 2015		882,000			$	85			$	99.53

	Second quarter 2015		709,000			$	85			$	94.06

	Third quarter 2015		906,000			$	85			$	91.25

	Fourth quarter 2015		869,000			$	85			$	92.19

	All oil collars		3,366,000

	Natural Gas Contracts

	Gas Swaps


	Contract Period		Volumes			Weighted-
						Average
						Contract
						Price
			(MMBtu)			(per MMBtu)
	First quarter 2015		23,548,000			$	4.22

	Second quarter 2015		15,985,000			$	3.9

	Third quarter 2015		14,950,000			$	4.03

	Fourth quarter 2015		13,570,000			$	4.02

2016		48,896,000			$	4.12

2017		37,414,000			$	4.16

2018		35,241,000			$	4.21

2019		28,159,000			$	4.28

All gas swaps*		217,763,000

____________________________________________
*Natural gas swaps are comprised of IF El Paso Permian (3%), IF HSC (82%), IF NGPL TXOK (1%), IF NNG Ventura (3%), and IF Enable East (11%).

Gas Collars


Contract Period		Volumes			Weighted-				Weighted-
					Average				Average
					Floor				Ceiling
					Price				Price
		(MMBtu)			(per MMBtu)				(per MMBtu)
First quarter 2015		2,524,000			$	4			$	4.3

Second quarter 2015		2,297,000			$	4			$	4.3

Third quarter 2015		2,005,000			$	4			$	4.3

Fourth quarter 2015		6,176,000			$	3.97			$	4.3

All gas collars*		13,002,000

____________________________________________
*Natural gas collars are comprised of IF El Paso Permian (4%), IF HSC (80%), IF NNG Ventura (8%), and IF Enable East (8%).
NGL Contracts
NGL Swaps


Contract Period		Volumes			Weighted-
					Average
					Contract
					Price
		(Bbls)			(per Bbl)
First quarter 2015		781,000			$	55.42

All NGL swaps*		781,000

____________________________________________
*NGL swaps are comprised of OPIS Natural Gasoline Mt Belv Non TET (28%) and OPIS Propane Mt Belv TET (72%).

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 $592.1 million and $21.5 million at December 31, 2014 and 2013, respectively.

The following tables detail the fair value of derivatives recorded in the accompanying balance sheets, by category:


	As of December 31, 2014
	Derivative Assets						Derivative Liabilities
	Balance Sheet		Fair Value				Balance Sheet		Fair Value
	Classification						Classification
	(in thousands)
Commodity Contracts	Current assets		$	402,668			Current liabilities		$	—

Commodity Contracts	Noncurrent assets		189,540				Noncurrent liabilities		70

Derivatives not designated as hedging instruments			$	592,208					$	70




	As of December 31, 2013
	Derivative Assets						Derivative Liabilities
	Balance Sheet		Fair Value				Balance Sheet		Fair Value
	Classification						Classification
	(in thousands)
Commodity Contracts	Current assets		$	21,559			Current liabilities		$	26,380

Commodity Contracts	Noncurrent assets		30,951				Noncurrent liabilities		4,640

Derivatives not designated as hedging instruments			$	52,510					$	31,020


Offsetting of Derivative Assets and Liabilities

As of December 31, 2014 and 2013, all derivative instruments held by the Company were subject to enforceable master netting arrangements held by various financial institutions. In general, the terms of the Company’s agreements provide for offsetting of amounts payable or receivable between it and the counterparty, at the election of both parties, for 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		2014				2013				2014				2013
		(in thousands)
Gross amounts presented in the accompanying balance sheets		$	592,208			$	52,510			$	(70	)		$	(31,020	)

Amounts not offset in the accompanying balance sheets		(70		)		(30,652		)		70				30,652

Net amounts		$	592,138			$	21,858			$	—			$	(368	)


Discontinuance of Cash Flow Hedge Accounting

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. Fair values at December 31, 2010, were frozen in AOCL as of the de-designation date and were reclassified into earnings as the original derivative transactions settled. As of September 30, 2013, all commodity derivative contracts that had been previously designated as cash flow hedges had settled and had been reclassified into earnings from AOCL.

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 AOCL. The Company had no derivatives designated as cash flow hedges for the years ended December 31, 2014, 2013, and 2012, and no new gains or losses were deferred to AOCL during these respective years. 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 presented in the accompanying statements of operations:


	For the Years Ended December 31,
	2014				2013				2012
	(in thousands)
Derivative settlement (gain) loss:
Oil contracts	$	(28,410	)		$	15,161			$	11,893

Gas contracts	26,706				(30,338		)		(47,270		)

NGL contracts	(10,911		)		(6,885		)		(8,887		)
Total derivative settlement gain (1)	$	(12,615	)		$	(22,062	)		$	(44,264	)

Total derivative (gain) loss:
Oil contracts	$	(457,082	)		$	14,665			$	(20,088	)

Gas contracts	(93,267		)		(14,053		)		(15,493		)
NGL contracts	(32,915		)		(3,692		)		(20,049		)
Total derivative gain (2)	$	(583,264	)		$	(3,080	)		$	(55,630	)
____________________________________________

(1)	Total derivative settlement gain is reported in the derivative cash settlements line item on the accompanying statements of cash flows within net cash provided by operating activities with the change in accrued settlements between years being reported in change in accounts receivable and change in accounts payable and accrued expenses line items. Total derivative settlement gains are adjusted by a $41.0 million decrease attributable to the change in current assets and liabilities at December 31, 2014.

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

The following table details the effect of derivative instruments on AOCL and the accompanying statements of operations (net of income tax):


			Location on		For the Years Ended December 31,
			Accompanying
			Statements of
	Derivatives		Operations		2014				2013				2012
					(in thousands)
Amount reclassified from AOCL	Commodity Contracts		Other operating revenues		$	—			$	1,115			$	(2,264	)


The realized net hedge loss for the year ended December 31, 2013, and net hedge gain for the year ended December 31, 2012, shown net of income tax in the table above, are comprised of realized 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 other operating revenues line item on the accompanying statements of operations. The Company realized a pre-tax net loss of $1.8 million and a pre-tax net gain of $3.9 million from its commodity derivative contracts that were previously designated as cash flow hedges for the years ended December 31, 2013, and 2012, respectively.

Credit Related Contingent Features

As of December 31, 2014, and through the filing date of this report, all of the Company’s derivative counterparties were members of the Company’s credit facility lender group. The Company’s obligations under its credit facility and derivative contracts are secured by liens on at least 75 percent 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, 2014
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Text Block]	Note 11 – Fair Value Measurements
	The Company follows fair value measurement authoritative accounting guidance for all assets and liabilities measured at fair value. 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, 2014:


		Level 1			Level 2			Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	592,208		$	—

	Proved oil and gas properties (2)	$	—		$	—		$	33,423

	Oil and gas properties held for sale (2)	$	—		$	—		$	17,891

	Liabilities:
	Derivatives (1)	$	—		$	70		$	—

	Net Profits Plan (1)	$	—		$	—		$	27,136

	____________________________________________
	(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, 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.

	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. 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 lender group.

	The methods described above may result in a fair value estimate that may not be indicative of net realizable value or may not be reflective of future fair values and cash flows. While the Company believes that the valuation methods utilized are appropriate and consistent with 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 derivative 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, 2014, would differ by approximately $2.6 million. A one percent increase or decrease in the discount rate would result in a change of approximately $1.1 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,
	2014			2013			2012
	(in thousands)
Beginning balance	$	56,985		$	78,827		$	107,731

Net increase (decrease) in liability (1)	(12,492		)	3,527			(9,251		)

Net settlements (1) (2)	(17,357		)	(25,369		)	(19,653		)
Transfers in (out) of Level 3	—			—			—

Ending balance	$	27,136		$	56,985		$	78,827

____________________________________________

-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 $8.3 million, $10.3 million, and $2.3 million relating to divestiture proceeds for the years ended December 31, 2014, 2013, and 2012, respectively.

Long-term Debt
The following table reflects the fair value of the Senior Notes measured using Level 1 inputs based on quoted secondary market trading prices. The Senior Notes were not presented at fair value on the accompanying balance sheets as of December 31, 2014 or 2013, as they are recorded at historical value.



	As of December 31,
	2014			2013
	(in thousands)
2019 Notes	$	350,018		$	374,290

2021 Notes	$	343,000		$	373,625

2022 Notes (1)	$	556,500		$	—

2023 Notes	$	379,000		$	422,000

2024 Notes	$	435,000		$	475,315

____________________________________________
(1) The 2022 Notes were issued on November 17, 2014.

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, 2014, and 2013. The Company believes that the discount rate is representative of current market conditions and takes into account estimates of future cash payments, expectations of possible variations in the amount and/or timing of cash flows, the risk premium, and nonperformance risk. The prices for oil and gas are forecasted based on 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, 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, proved oil and gas properties measured at fair value within the accompanying balance sheets totaled $33.4 million and $62.2 million as of December 31, 2014, and 2013, 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 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.
Impaired unproved oil and gas properties measured at fair value were written down to zero and $3.3 million in the accompanying balance sheets as of December 31, 2014, and 2013, respectively.

The fair value measurements of assets acquired and liabilities assumed are measured on a nonrecurring basis on the acquisition date using an income valuation technique based on inputs that are not observable in the market and therefore represent Level 3 inputs. Significant inputs to the valuation of acquired oil and gas properties include estimates of: (i) reserves; (ii) production rates; (iii) future operating and development costs; (iv) future commodity prices, including price differentials; (v) future cash flows; and (vi) a market participant-based weighted average cost of capital rate. These inputs require significant judgments and estimates by the Company’s management at the time of the valuation. Refer to Note 3 - Acquisitions, Divestitures, and Assets Held for Sale for additional information on the fair value of assets acquired during 2014.

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.

Acquisition_and_Development_Ag

Acquisition and Development Agreement and Carry and Earning Agreement	12 Months Ended
	Dec. 31, 2014
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 expended an aggregate $680.0 million on behalf of the Company. 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.

	During the second quarter of 2014, the remainder of the carry under the Acquisition and Development Agreement was expended. Accordingly, the Company accrued and funded its full share of drilling and completion costs in its non-operated Eagle Ford shale program for the remainder of 2014.

Suspended_Well_Costs

Suspended Well Costs	12 Months Ended
	Dec. 31, 2014
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 2014, 2013, and 2012. 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,
		2014			2013			2012
		(in thousands)
	Beginning balance on January 1,	$	34,527		$	9,100		$	18,600

	Additions to capitalized exploratory well costs pending the determination of proved reserves	43,589			34,527			9,100

	Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	(33,340		)	(9,100		)	(5,865		)
	Capitalized exploratory well costs charged to expense	(1,187		)	—			(12,735		)

	Ending balance at December 31,	$	43,589		$	34,527		$	9,100

	As of December 31, 2014, there were no exploratory well costs that were capitalized for more than one year.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2014
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, 2014, through the filing date of this report.
	Certain prior period amounts have been reclassified to conform to the current period presentation on the accompanying financial statements. The Company’s refundable income taxes are combined and presented in the prepaid expenses and other financial statement line item within the accompanying balance sheets. The Company’s land and materials inventory are combined and presented in the other property and equipment, net of accumulated depreciation financial statement line item within the accompanying balance sheets. Lastly, the asset retirement obligation associated with oil and gas properties held for sale is no longer separately presented and is presented in the asset retirement obligation financial statement line item within the accompanying balance sheets. Within the accompanying consolidated statements of operations (“accompanying statements of operations”), the Company’s realized hedge gain (loss) is combined and presented in the other operating revenues financial statement line item. In the accompanying consolidated statements of cash flows (“accompanying statements of cash flows”) in cash flows from operating activities, refundable income taxes is now combined and presented with prepaid expenses and other. Additionally, receipts from restricted cash related to any like-kind exchanges under Section 1031 of the Internal Revenue Code are now combined and presented in the other, net financial statement line item within net cash used in investing activities on the accompanying statements of cash flows.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates in the Preparation of Financial Statements
Use of Estimates, Policy [Policy Text Block]	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 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
Cash and Cash Equivalents, Policy [Policy Text Block]	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.
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	Restricted Cash
	The Company has no restricted cash at December 31, 2014. The restricted cash balance at December 31, 2013, mainly consisted of cash payments that were 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 classified as non-current assets. Please refer to Note 12 - Acquisition and Development Agreement for additional information.
Receivables, Policy [Policy Text Block]	Accounts Receivable
Receivables, Policy [Policy Text Block]	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.
Full Cost or Successful Efforts, Policy [Policy Text Block]	Oil and Gas Producing Activities
Full Cost or Successful Efforts, Policy [Policy Text Block]	The Company accounts for its oil and gas exploration and development costs using the successful efforts method. G&G 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.
Property, Plant and Equipment, Policy [Policy Text Block]	Other Property and Equipment
Property, Plant and Equipment, Policy [Policy Text Block]	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 30 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.
Internal-Use Software Development Costs [Policy Text Block]	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.
Net Profits Plan [Policy Text Block]	Net Profits Plan

	The Company records the estimated fair value of expected future payments to be 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 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
Asset Retirement Obligations, Policy [Policy Text Block]	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
Revenue Recognition, Policy [Policy Text Block]	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.
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 proved developed 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.
Disposition of Proved and Unproved Property [Policy Text Block]	Sales of Proved and Unproved Properties

	The partial sale of proved property 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 – Acquisitions, Divestitures, and Assets Held for Sale.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Stock-Based Compensation

	At December 31, 2014, the Company had stock-based employee compensation plans that included RSUs, PSUs, and restricted stock awards 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
Income Tax, Policy [Policy Text Block]	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.
Segment Reporting, Policy [Policy Text Block]	Industry Segment and Geographic Information
Segment Reporting, Policy [Policy Text Block]	The Company operates 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 (“SPE”), which would have been established for the purpose of facilitating off-balance sheet arrangements or other contractually narrow or limited purposes.
	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.
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, 2014
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, 2014
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, 2014
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, 2014
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,
		2014			2013			2012
		(in thousands)
	Dilutive	814			1,383			—

	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,
		2014				2013			2012
		(in thousands, except per share amounts)
	Net income (loss)	$	666,051			$	170,935		$	(54,249	)

	Basic weighted-average common shares outstanding	67,230				66,615			65,138

	Add: dilutive effect of stock options, unvested RSUs, and contingent PSUs	814				1,383			—

	Add: dilutive effect of 3.50% Senior Convertible Notes (1)	—				—			—

	Diluted weighted-average common shares outstanding	68,044				67,998			65,138

	Basic net income (loss) per common share	$	9.91			$	2.57		$	(0.83	)

	Diluted net income (loss) per common share	$	9.79			$	2.51		$	(0.83	)

	____________________________________________
	(1) For the year ended December 31, 2012, the shares into which the 3.50% Senior Convertible Notes were convertible were anti-dilutive and excluded from the calculation of diluted earnings per share.
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 Adjustments				Pension Liability Adjustments
		(in thousands)
	For the year ended December 31, 2012
	Net actuarial loss					$	(4,680	)
	Reclassification to earnings	$	(3,865	)		771

	Tax benefit	1,601				1,439

	Loss, net of tax	$	(2,264	)		$	(2,470	)
	For the year ended December 31, 2013
	Net actuarial gain					$	2,766

	Reclassification to earnings	$	1,777			1,239

	Tax expense	(662		)		(1,522		)
	Income, net of tax	$	1,115			$	2,483

	For the year ended December 31, 2014
	Net actuarial loss					$	(10,062	)
	Reclassification to earnings	$	—			706

	Tax benefit	—				3,460

	Loss, net of tax	$	—			$	(5,896	)

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, 2014
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,
		2014		2013

		(in thousands)
	Accrued oil, gas, and NGL production revenue	$	180,250	$	228,169

	Amounts due from joint interest owners	58,347		37,517

	Accrued derivative settlements	39,811		770

	State severance tax refunds	24,394		29,213

	Other	19,828		22,702

	Total accounts receivable	$	322,630	$	318,371

Schedule of Accounts Payable and Accrued Liabilities [Table Text Block]	Accounts payable and accrued expenses are comprised of the following:


		As of December 31,
		2014		2013
		(in thousands)
	Accrued capital expenditures	$	357,156	$	217,820

	Revenue and severance tax payable	63,779		87,852

	Accrued lease operating expense	34,822		29,296

	Accrued property taxes	15,059		10,401

	Joint owner advances	152		96,636

	Accrued compensation	56,279		71,466

	Accrued interest	40,786		40,027

	Other	72,651		53,253

	Total accounts payable and accrued expenses	$	640,684	$	606,751

Divestitures_and_Assets_Held_f1

Divestitures and Assets Held for Sale Fair Value of Acquired Properties (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Net Assets Acquired [Table Text Block]

		As of September 24, 2014			As of October 15, 2014
	Purchase Price	(in thousands)
	Cash consideration	$	325,230		$	84,836


	Fair value of assets acquired:
	Proved oil and gas properties	$	203,493		$	54,360

	Unproved oil and gas properties	126,622			29,469

	Total fair value of oil and gas properties acquired	330,115			83,829


	Working capital	(2,772		)	2,625

	Asset retirement obligation	(2,113		)	(1,618		)
	Total fair value of net assets acquired	$	325,230		$	84,836

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
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,
			2014				2013				2012
			(in thousands)
	Current portion of income tax expense
	Federal		$	—			$	—			$	—

	State		868				2,121				370

	Deferred portion of income tax expense (benefit)		397,780				105,555				(29,638		)

	Total income tax expense (benefit)		$	398,648			$	107,676			$	(29,268	)

	Effective tax rate		37.4		%		38.6		%		35		%
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,
			2014				2013
			(in thousands)
	Deferred tax liabilities:
	Oil and gas properties		$	1,029,424			$	768,463

	Derivative asset		220,437				9,529

	Other		4,475				1,245

	Total deferred tax liabilities		1,254,336				779,237

	Deferred tax assets:

	Federal and state tax net operating loss carryovers		184,447				91,788

	Stock compensation		16,763				18,820

	Other long-term liabilities		16,301				13,341

	Net Profits Plan liability		9,414				20,913

	Total deferred tax assets		226,925				144,862

	Valuation allowance		(7,246		)		(5,001		)
	Net deferred tax assets		219,679				139,861

	Total net deferred tax liabilities		1,034,657				639,376

	Less: current deferred income tax liabilities		(152,082		)		(172		)
	Add: current deferred income tax assets		9,106				10,921

	Non-current net deferred tax liabilities		$	891,681			$	650,125

	Current federal income tax refundable		$	4,734			$	4,630

	Current state income tax refundable		$	—			$	—

	Current state income tax payable		$	25			$	1,460

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	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,
		2014				2013				2012
		(in thousands)
	Federal statutory tax expense (benefit)	$	372,644			$	97,514			$	(29,231	)

	Increase (decrease) in tax resulting from:
	State tax expense (benefit) (net of federal benefit)	21,350				9,400				(992		)

	Research and development credit	—				—				(970		)

	Change in valuation allowance	2,245				(314		)		1,524

	Other	2,409				1,076				401

	Income tax expense (benefit)	$	398,648			$	107,676			$	(29,268	)

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,
		2014				2013				2012
		(in thousands)
	Beginning balance	$	2,358			$	2,278			$	1,961

	Additions for tax positions of prior years	140				80				317

	Settlements	(916		)		—				—

	Ending balance	$	1,582			$	2,358			$	2,278

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2014
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		1.25	%	1.5	%	1.75	%		2	%	2.25	%
	ABR Loans or Swingline Loans		0.25	%	0.5	%	0.75	%		1	%	1.25	%
	Commitment Fee Rate		0.3	%	0.3	%	0.35	%		0.375	%	0.375	%
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 18, 2015, December 31, 2014, and December 31, 2013:



		As of February 18, 2015			As of December 31, 2014			As of December 31, 2013
		(in thousands)
	Credit facility balance	$	341,000		$	166,000		$	—
	Credit facility balance	$	341,000		$	166,000		$	—
	Letters of credit (1)	$	808		$	808		$	808
	Letters of credit (1)	$	808		$	808		$	808
	Available borrowing capacity	$	1,158,192		$	1,333,192		$	1,299,192
	Available borrowing capacity	$	1,158,192		$	1,333,192		$	1,299,192
	____________________________________________
	(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, 2014, and 2013, consisted of the following:


		As of December 31,
		2014			2013
		(in thousands)
	2019 Notes	$	350,000		$	350,000
	2019 Notes	$	350,000		$	350,000
	2021 Notes	350,000			350,000
	2021 Notes	350,000			350,000
	2022 Notes	600,000			—
	2022 Notes	600,000			—
	2023 Notes	400,000			400,000
	2023 Notes	400,000			400,000
	2024 Notes	500,000			500,000
	2024 Notes	500,000			500,000
	Total Senior Notes	$	2,200,000		$	1,600,000
	Total Senior Notes	$	2,200,000		$	1,600,000
Schedule of Debt Instrument Redemption Price, 6.125% Senior Notes Due 2022 [Table Text Block]	On or after November 15, 2018, the Company may also redeem all or, from time to time, a portion of the 2022 Notes at the redemption prices set forth below, during the twelve-month period beginning on November 15 of each applicable year, expressed as a percentage of the principal amount redeemed, plus accrued and unpaid interest:



	2018	103.063	%
	2019	101.531	%
	2020 and thereafter	100	%
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 redeem all or, from time to time, a portion of the 2019 Notes on or after February 15, 2015, at the prices set forth in the table 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, 2014
Commitments and Contingencies Disclosure [Abstract]
Long-term Purchase Commitment [Table Text Block]	The annual minimum payments for the next five years and total minimum payments thereafter are presented below:


	Years Ending December 31,	(in thousands)
	2015	$	224,897

	2016	147,896

	2017	118,320

	2018	128,866

	2019	132,920

	Thereafter	383,619

	Total	$	1,136,518

Compensation_Plans_Tables

Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2014
Compensation Related Costs [Abstract]
Schedule of performance share awards under equity incentive compensation plan	A summary of the status and activity of non-vested PSUs is presented in the following table:																[1]


		For the Years Ended December 31,
		2014						2013					2012
		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)	572,469		$	66.07			669,308			$	63.91	885,894		$	57.52

	Granted (1)	202,404		$	94.66			274,831			$	64.13	314,853		$	51.98

	Vested (1)	(206,830	)	$	64.79			(345,005	)		$	60.06	(493,679	)	$	44.72

	Forfeited (1)	(134,383	)	$	86.72			(26,665	)		$	69.74	(37,760	)	$	65.35

	Non-vested at end of year(1)	433,660		$	73.63			572,469			$	66.07	669,308		$	63.91

	____________________________________________

	-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 Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]	A summary of the status and activity of non-vested RSUs is presented below:


		For the Years Ended December 31,
		2014						2013					2012
		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	580,431		$	57.05			496,244			$	51.81	308,877		$	44.33

	Granted	234,560		$	83.98			329,939			$	60.01	379,332		$	49.47

	Vested	(253,031	)	$	58.19			(207,376	)		$	49.73	(166,672	)	$	32.72

	Forfeited	(46,236	)	$	62.06			(38,376	)		$	54.37	(25,293	)	$	51.06

	Non-vested at end of year	515,724		$	68.29			580,431			$	57.05	496,244		$	51.81

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, 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

	For the year ended December 31, 2014
	Outstanding, start of year	39,088		$	20.87

	Exercised	(39,088	)	$	20.87			$	1,993,726

	Forfeited	—		$	—

	Outstanding, end of year	—		$	—			$	—

	Vested and exercisable at end of year	—		$	—			$	—

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,
		2014		2013			2012
	Risk free interest rate	0.1	%	0.1	%		0.1	%
	Dividend yield	0.1	%	0.2	%		0.2	%
	Volatility factor of the expected market	33	%	41.1	%		47.8	%
	price of the Company’s common stock
	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,
		2014			2013				2012
		(in thousands)
	General and administrative expense	$	8,326		$	13,734			$	15,565

	Exploration expense	690			1,310				1,751

	Total	$	9,016		$	15,044			$	17,316


[1]	(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.

Pension_Benefits_Tables

Pension Benefits (Tables)	12 Months Ended
Pension Benefits (Tables)	Dec. 31, 2014
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,
		2014				2013
		(in thousands)
	Change in benefit obligation:
	Projected benefit obligation at beginning of year	$	43,285			$	40,237
	Projected benefit obligation at beginning of year	$	43,285			$	40,237
	Service cost	6,335				6,291
	Service cost	6,335				6,291
	Interest cost	2,191				1,627
	Interest cost	2,191				1,627
	Plan amendments	—				—
	Plan amendments	—				—
	Actuarial (gain) loss	8,821				(1,577		)
	Actuarial (gain) loss	8,821				(1,577		)
	Benefits paid	(2,765		)		(3,293		)
	Projected benefit obligation at end of year	57,867				43,285
	Projected benefit obligation at end of year	57,867				43,285

	Change in plan assets:
	Fair value of plan assets at beginning of year	24,658				20,254
	Fair value of plan assets at beginning of year	24,658				20,254
	Actual return on plan assets	737				2,726
	Actual return on plan assets	737				2,726
	Employer contribution	5,310				4,971
	Employer contribution	5,310				4,971
	Benefits paid	(2,765		)		(3,293		)
	Fair value of plan assets at end of year	27,940				24,658
	Fair value of plan assets at end of year	27,940				24,658
	Funded status at end of year	$	(29,927	)		$	(18,627	)
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	Accumulated Benefit Obligation in Excess of Plan Assets for the Pension Plans


		As of December 31,
		2014				2013
		(in thousands)
	Projected benefit obligation	$	57,867			$	43,285
	Projected benefit obligation	$	57,867			$	43,285

	Accumulated benefit obligation	$	43,205			$	32,396
	Accumulated benefit obligation	$	43,205			$	32,396
	Less: Fair value of plan assets	(27,940		)		(24,658		)
	Underfunded accumulated benefit obligation	$	15,265			$	7,738
	Underfunded accumulated benefit obligation	$	15,265			$	7,738
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, 2014 and 2013, consist of:


		As of December 31,
		2014				2013
		(in thousands)
	Unrecognized actuarial losses	$	17,812			$	8,439
	Unrecognized actuarial losses	$	17,812			$	8,439
	Unrecognized prior service costs	118				136
	Unrecognized prior service costs	118				136
	Unrecognized transition obligation	—				—
	Unrecognized transition obligation	—				—
	Accumulated other comprehensive loss	$	17,930			$	8,575
	Accumulated other comprehensive loss	$	17,930			$	8,575
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 2014, 2013, and 2012, were as follows:


		For the Years Ended December 31,
		2014				2013				2012
		(in thousands)
	Net actuarial gain (loss)	$	(10,062	)		$	2,766			$	(4,680	)
	Net actuarial gain (loss)	$	(10,062	)		$	2,766			$	(4,680	)
	Prior service cost	—				—				—
	Prior service cost	—				—				—
	Less: Amortization of:
	Prior service cost	(17		)		(17		)		(17		)
	Actuarial loss	(689		)		(1,222		)		(754		)
	Total other comprehensive income (loss)	$	(9,356	)		$	4,005			$	(3,909	)
	Total other comprehensive income (loss)	$	(9,356	)		$	4,005			$	(3,909	)
Components of the net periodic benefit cost for both the Qualified and the Nonqualified Pension Plan	Components of Net Periodic Benefit Cost for the Pension Plans


		For the Years Ended December 31,
		2014				2013				2012
		(in thousands)
	Components of net periodic benefit cost:
	Service cost	$	6,335			$	6,291			$	4,934
	Service cost	$	6,335			$	6,291			$	4,934
	Interest cost	2,191				1,627				1,374
	Interest cost	2,191				1,627				1,374
	Expected return on plan assets that reduces periodic pension cost	(1,978		)		(1,538		)		(1,165		)
	Amortization of prior service cost	17				17				17
	Amortization of prior service cost	17				17				17
	Amortization of net actuarial loss	689				1,222				754
	Amortization of net actuarial loss	689				1,222				754
	Net periodic benefit cost	$	7,254			$	7,619			$	5,914
	Net periodic benefit cost	$	7,254			$	7,619			$	5,914
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,
		2014		2013		2012
	Projected benefit obligation
	Discount rate	4.30%		5.00%		3.90%
	Rate of compensation increase	6.20%		6.20%		6.20%
	Net periodic benefit cost
	Discount rate	5.00%		3.90%		4.70%
	Expected return on plan assets (1)	7.50%		7.50%		7.50%
	Rate of compensation increase	6.20%		6.20%		6.20%
	____________________________________________

	-1	There is no assumed expected return on plan assets for the Nonqualified Pension Plan because there are no plan assets in the Nonqualified Pension Plan.
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		2015			2014			2013
	Equity securities		42	%		39.6	%		43.6	%
	Fixed income securities		35	%		33.9	%		32.2	%
	Other securities		23	%		26.5	%		24.2	%
	Total		100	%		100	%		100	%
	The fair values of the Company’s Qualified Pension Plan assets as of December 31, 2014 and 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
		Actual Asset Allocation			Total				Level 1 Inputs				Level 2 Inputs			Level 3 Inputs
					(in thousands)
	31-Dec-14
	Cash	—	%		$	—			$	—			$	—		$	—
	Cash	—	%		$	—			$	—			$	—		$	—
	Equity Securities
	Equity Securities
	Domestic (1)	27.1	%		7,569				5,550				2,019			—
	Domestic (1)	27.1	%		7,569				5,550				2,019			—
	International (2)	12.5	%		3,498				3,498				—			—
	International (2)	12.5	%		3,498				3,498				—			—
	Total Equity Securities	39.6	%		11,067				9,048				2,019			—
	Total Equity Securities	39.6	%		11,067				9,048				2,019			—
	Fixed Income Securities
	Fixed Income Securities
	High-Yield Bonds (3)	2.9	%		797				797				—			—
	High-Yield Bonds (3)	2.9	%		797				797				—			—
	Core Fixed Income (4)	22.4	%		6,247				6,247				—			—
	Core Fixed Income (4)	22.4	%		6,247				6,247				—			—
	Floating Rate Corp Loans (5)	8.6	%		2,413				2,413				—			—
	Floating Rate Corp Loans (5)	8.6	%		2,413				2,413				—			—
	Total Fixed Income Securities	33.9	%		9,457				9,457				—			—
	Total Fixed Income Securities	33.9	%		9,457				9,457				—			—
	Other Securities:
	Other Securities:
	Commodities (6)	2.9	%		810				810				—			—
	Commodities (6)	2.9	%		810				810				—			—
	Real Estate (7)	4.7	%		1,327				—				—			1,327
	Real Estate (7)	4.7	%		1,327				—				—			1,327
	Hedge Fund (8)	14.8	%		4,130				593				—			3,537
	Hedge Fund (8)	14.8	%		4,130				593				—			3,537
	Collective Investment Trusts (9)	4.1	%		1,149				—				1,149			—
	Collective Investment Trusts (9)	4.1	%		1,149				—				1,149			—
	Total Other Securities	26.5	%		7,416				1,403				1,149			4,864
	Total Other Securities	26.5	%		7,416				1,403				1,149			4,864
	Total Investments	100	%		$	27,940			$	19,908			$	3,168		$	4,864
	Total Investments	100	%		$	27,940			$	19,908			$	3,168		$	4,864

	31-Dec-13
	Cash and Money Market Funds	—	%		$	—			$	—			$	—		$	—
	Cash and Money Market Funds	—	%		$	—			$	—			$	—		$	—
	Equity Securities
	Domestic (1)	29.9	%		7,371				4,888				2,483			—
	Domestic (1)	29.9	%		7,371				4,888				2,483			—
	International (2)	13.7	%		3,373				3,373				—			—
	International (2)	13.7	%		3,373				3,373				—			—
	Total Equity Securities	43.6	%		10,744				8,261				2,483			—
	Total Equity Securities	43.6	%		10,744				8,261				2,483			—
	Fixed Income Securities
	High-Yield Bonds (3)	5.9	%		1,448				1,448				—			—
	High-Yield Bonds (3)	5.9	%		1,448				1,448				—			—
Core Fixed Income (4)	20.3	%		5,006				5,006				—			—
Core Fixed Income (4)	20.3	%		5,006				5,006				—			—
Floating Rate Corp Loans (5)	6	%		1,483				1,483				—			—
Floating Rate Corp Loans (5)	6	%		1,483				1,483				—			—
Total Fixed Income Securities	32.2	%		7,937				7,937				—			—
Total Fixed Income Securities	32.2	%		7,937				7,937				—			—
Other Securities:
Commodities (6)	3.8	%		945				945				—			—
Commodities (6)	3.8	%		945				945				—			—
Real Estate (7)	3.5	%		859				—				—			859
Real Estate (7)	3.5	%		859				—				—			859
Hedge Fund (8)	14.3	%		3,517				955				—			2,562
Hedge Fund (8)	14.3	%		3,517				955				—			2,562
Collective Investment Trusts (9)	2.6	%		656				—				656			—
Collective Investment Trusts (9)	2.6	%		656				—				656			—
Total Other Securities	24.2	%		5,977				1,900				656			3,421
Total Other Securities	24.2	%		5,977				1,900				656			3,421
Total Investments	100	%		$	24,658			$	18,098			$	3,139		$	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.
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):


	Balance at January 1, 2013	$	2,384
	Balance at January 1, 2013	$	2,384
	Purchases	742
	Purchases	742
	Realized gain on assets	161
	Realized gain on assets	161
	Unrealized gain on assets	134
	Unrealized gain on assets	134
	Balance at December 31, 2013	$	3,421
	Balance at December 31, 2013	$	3,421
	Purchases	1,232
	Purchases	1,232
	Realized gain on assets	144
	Realized gain on assets	144
	Unrealized gain on assets	67
	Unrealized gain on assets	67
	Balance at December 31, 2014	$	4,864
	Balance at December 31, 2014	$	4,864
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)
	2015		$	3,006
	2015		$	3,006
	2016		$	3,046
	2016		$	3,046
	2017		$	3,921
	2017		$	3,921
	2018		$	4,558
	2018		$	4,558
	2019		$	5,204
	2019		$	5,204
	2020 through 2024		$	38,427
	2020 through 2024		$	38,427

Asset_Retirement_Obligations_R

Asset Retirement Obligations Reconciliation of Asset Retirement Obligation Liability (Tables)	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation [Abstract]
Schedule of Change in Asset Retirement Obligation [Table Text Block]	A reconciliation of the Company’s total asset retirement obligation liability is as follows:


		As of December 31,
		2014			2013
		(in thousands)
	Beginning asset retirement obligation	$	121,186		$	120,518

	Liabilities incurred	13,506			18,682

	Liabilities settled	(11,372		)	(33,129		)
	Accretion expense	6,090			5,997

	Revision to estimated cash flows	(7,286		)	9,118

	Ending asset retirement obligation	$	122,124		$	121,186

Derivative_Financial_Instrumen2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	The following tables summarize the approximate volumes and average contract prices of contracts the Company had in place as of December 31, 2014:
	Oil Contracts
	Oil Swaps


	Contract Period		NYMEX WTI Volumes			Weighted-
						Average
						Contract
						Price
			(Bbls)			(per Bbl)
	First quarter 2015		1,711,000			$	91.96

	Second quarter 2015		1,639,000			$	91.26

	Third quarter 2015		1,254,000			$	90.78

	Fourth quarter 2015		1,137,000			$	90.15

	2016		5,570,000			$	88.01

	All oil swaps		11,311,000


	Oil Collars


	Contract Period		NYMEX WTI			Weighted-				Weighted-
			Volumes			Average				Average
						Floor				Ceiling
						Price				Price
			(Bbls)			(per Bbl)				(per Bbl)
	First quarter 2015		882,000			$	85			$	99.53

	Second quarter 2015		709,000			$	85			$	94.06

	Third quarter 2015		906,000			$	85			$	91.25

	Fourth quarter 2015		869,000			$	85			$	92.19

	All oil collars		3,366,000

	Natural Gas Contracts

	Gas Swaps


	Contract Period		Volumes			Weighted-
						Average
						Contract
						Price
			(MMBtu)			(per MMBtu)
	First quarter 2015		23,548,000			$	4.22

	Second quarter 2015		15,985,000			$	3.9

	Third quarter 2015		14,950,000			$	4.03

	Fourth quarter 2015		13,570,000			$	4.02

	2016		48,896,000			$	4.12

	2017		37,414,000			$	4.16

	2018		35,241,000			$	4.21

2019		28,159,000			$	4.28

All gas swaps*		217,763,000

____________________________________________
*Natural gas swaps are comprised of IF El Paso Permian (3%), IF HSC (82%), IF NGPL TXOK (1%), IF NNG Ventura (3%), and IF Enable East (11%).

Gas Collars


Contract Period		Volumes			Weighted-				Weighted-
					Average				Average
					Floor				Ceiling
					Price				Price
		(MMBtu)			(per MMBtu)				(per MMBtu)
First quarter 2015		2,524,000			$	4			$	4.3

Second quarter 2015		2,297,000			$	4			$	4.3

Third quarter 2015		2,005,000			$	4			$	4.3

Fourth quarter 2015		6,176,000			$	3.97			$	4.3

All gas collars*		13,002,000

____________________________________________
*Natural gas collars are comprised of IF El Paso Permian (4%), IF HSC (80%), IF NNG Ventura (8%), and IF Enable East (8%).
NGL Contracts
NGL Swaps


Contract Period		Volumes			Weighted-
					Average
					Contract
					Price
		(Bbls)			(per Bbl)
First quarter 2015		781,000			$	55.42

All NGL swaps*		781,000

____________________________________________
*NGL swaps are comprised of OPIS Natural Gasoline Mt Belv Non TET (28%) and OPIS Propane Mt Belv TET (72%).
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, 2014
		Derivative Assets						Derivative Liabilities
		Balance Sheet		Fair Value				Balance Sheet		Fair Value
		Classification						Classification
		(in thousands)
	Commodity Contracts	Current assets		$	402,668			Current liabilities		$	—

	Commodity Contracts	Noncurrent assets		189,540				Noncurrent liabilities		70

	Derivatives not designated as hedging instruments			$	592,208					$	70




		As of December 31, 2013
		Derivative Assets						Derivative Liabilities
		Balance Sheet		Fair Value				Balance Sheet		Fair Value
		Classification						Classification
		(in thousands)
	Commodity Contracts	Current assets		$	21,559			Current liabilities		$	26,380

	Commodity Contracts	Noncurrent assets		30,951				Noncurrent liabilities		4,640

	Derivatives not designated as hedging instruments			$	52,510					$	31,020

Schedule of the potential effects of master netting arrangements	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		2014				2013				2014				2013
			(in thousands)
	Gross amounts presented in the accompanying balance sheets		$	592,208			$	52,510			$	(70	)		$	(31,020	)

	Amounts not offset in the accompanying balance sheets		(70		)		(30,652		)		70				30,652

	Net amounts		$	592,138			$	21,858			$	—			$	(368	)

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 presented in the accompanying statements of operations:


		For the Years Ended December 31,
		2014				2013				2012
		(in thousands)
	Derivative settlement (gain) loss:
	Oil contracts	$	(28,410	)		$	15,161			$	11,893

	Gas contracts	26,706				(30,338		)		(47,270		)

	NGL contracts	(10,911		)		(6,885		)		(8,887		)
	Total derivative settlement gain (1)	$	(12,615	)		$	(22,062	)		$	(44,264	)

	Total derivative (gain) loss:
	Oil contracts	$	(457,082	)		$	14,665			$	(20,088	)

	Gas contracts	(93,267		)		(14,053		)		(15,493		)
	NGL contracts	(32,915		)		(3,692		)		(20,049		)
	Total derivative gain (2)	$	(583,264	)		$	(3,080	)		$	(55,630	)
	____________________________________________

	(1)	Total derivative settlement gain is reported in the derivative cash settlements line item on the accompanying statements of cash flows within net cash provided by operating activities with the change in accrued settlements between years being reported in change in accounts receivable and change in accounts payable and accrued expenses line items. Total derivative settlement gains are adjusted by a $41.0 million decrease attributable to the change in current assets and liabilities at December 31, 2014.

	(2)	Total derivative gain is reported in the derivative gain line item on the accompanying 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 AOCL and the accompanying statements of operations (net of income tax):


				Location on		For the Years Ended December 31,
				Accompanying
				Statements of
		Derivatives		Operations		2014				2013				2012
						(in thousands)
	Amount reclassified from AOCL	Commodity Contracts		Other operating revenues		$	—			$	1,115			$	(2,264	)

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	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, 2014:										[1],[2]


		Level 1			Level 2			Level 3
		(in thousands)
	Assets:
	Derivatives (1)	$	—		$	592,208		$	—

	Proved oil and gas properties (2)	$	—		$	—		$	33,423

	Oil and gas properties held for sale (2)	$	—		$	—		$	17,891

	Liabilities:
	Derivatives (1)	$	—		$	70		$	—

	Net Profits Plan (1)	$	—		$	—		$	27,136

	____________________________________________
	(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, 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.
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,
		2014			2013			2012
		(in thousands)
	Beginning balance	$	56,985		$	78,827		$	107,731

	Net increase (decrease) in liability (1)	(12,492		)	3,527			(9,251		)

	Net settlements (1) (2)	(17,357		)	(25,369		)	(19,653		)
	Transfers in (out) of Level 3	—			—			—

	Ending balance	$	27,136		$	56,985		$	78,827

	____________________________________________

	-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 $8.3 million, $10.3 million, and $2.3 million relating to divestiture proceeds for the years ended December 31, 2014, 2013, and 2012, respectively.
Schedule of Long-term Debt Instruments [Table Text Block]	The following table reflects the fair value of the Senior Notes measured using Level 1 inputs based on quoted secondary market trading prices. The Senior Notes were not presented at fair value on the accompanying balance sheets as of December 31, 2014 or 2013, as they are recorded at historical value.



		As of December 31,
		2014			2013
		(in thousands)
	2019 Notes	$	350,018		$	374,290

	2021 Notes	$	343,000		$	373,625

	2022 Notes (1)	$	556,500		$	—

	2023 Notes	$	379,000		$	422,000

	2024 Notes	$	435,000		$	475,315

	____________________________________________
	(1) The 2022 Notes were issued on November 17, 2014.

[1]	(1) This represents a financial asset or liability that is measured at fair value on a recurring basis.
[2]	(2) This represents a non-financial asset that is measured at fair value on a nonrecurring basis.

Suspended_Well_Costs_Tables

Suspended Well Costs (Tables)	12 Months Ended
	Dec. 31, 2014
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 2014, 2013, and 2012. 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,
		2014			2013			2012
		(in thousands)
	Beginning balance on January 1,	$	34,527		$	9,100		$	18,600

	Additions to capitalized exploratory well costs pending the determination of proved reserves	43,589			34,527			9,100

	Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	(33,340		)	(9,100		)	(5,865		)
	Capitalized exploratory well costs charged to expense	(1,187		)	—			(12,735		)

	Ending balance at December 31,	$	43,589		$	34,527		$	9,100

Summary_of_Significant_Account3

Summary of Significant Accounting Policies Other (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Years	Dec. 31, 2013	Dec. 31, 2012
Basis of Presentation and Significant Accounting Policies [Line Items]
Restricted Cash and Cash Equivalents	$0
Revolving credit facility	166,000,000	0
Allowance for Doubtful Accounts Receivable	0	0
Capitalization of Development and Implementation of Internal Use Software	35,000,000	11,200,000
Concentration of Credit Risk and Major Customers [Abstract]
Number of Major Customers	1	3	2
Marketing agreement length for gathering, transportation, and processing through-put commitments	10
Number of Derivative Counterparties	9
Property, Plant and Equipment [Abstract]
Property, Plant, and Equipment, Salvage Value	50,800,000	57,500,000
Inventory, Net [Abstract]
Property, Plant and Equipment, Estimated Useful Lives	three to 30 years
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	84,480,000	172,641,000	208,923,000
Abandonment and impairment of unproved properties	75,638,000	46,105,000	16,342,000
Regency Gas Services, LLC [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage		26.00%	21.00%
Anadarko Petroleum Company [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage	19.00%	16.00%
Plains Marketing, LP [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage		12.00%	13.00%
Unnamed Major Customer with Related Entities [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage	14.00%
Number of Entities Related to One Unnamed Customer	4
Maximum Percentage of Total Production Revenue for Individual Entity	10.00%
Convertible Debt [Member]
Debt Instruments [Abstract]
Debt Instrument, Convertible, Conversion Price			$54.42
Debt Instrument, Principal Amount Denominator for Conversion into Common Stock			$1,000
Convertible Debt [Member] \| Convertible Debt [Member]
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage			3.50%
Debt instrument convertible conversion rate			864,106

Summary_of_Significant_Account4

Summary of Significant Accounting Policies Earnings Per Share (Details) (USD $)	12 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0		0		2,102
Earnings Per Share Reconciliation [Abstract]
Net Income (loss)	$666,051,000		$170,935,000		($54,249,000)
Weighted Average Number of Shares Outstanding, Basic	67,230		66,615		65,138
Incremental Common Shares Attributable to Share-based Payment Arrangements	814		1,383		0
Incremental Common Shares Attributable to Conversion of Debt Securities	0	[1]	0	[1]	0	[1]
Weighted Average Number of Shares Outstanding, Diluted	68,044		67,998		65,138
Basic net income (loss) per common share	$9.91		$2.57		($0.83)
Diluted net income (loss) per common share	$9.79		$2.51		($0.83)
Convertible Debt [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Debt Instrument, Principal Amount Denominator for Conversion into Common Stock					1,000
Debt Instrument, Convertible, Conversion Price					$54.42
Retained Earnings
Earnings Per Share Reconciliation [Abstract]
Net Income (loss)	$666,051,000		$170,935,000		($54,249,000)

[1]	(1) For the year ended December 31, 2012, the shares into which the 3.50% Senior Convertible Notes were convertible were anti-dilutive and excluded from the calculation of diluted earnings per share.

Summary_of_Significant_Account5

Summary of Significant Accounting Policies Other Comprehensive Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Other comprehensive income [Abstract]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Actuarial Gain (Loss), before Tax	($10,062)		$2,766		($4,680)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Reclassification to Earnings, before Tax	0		1,777		-3,865
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Reclassification to Earnings, Tax	0		662		-1,601
Reclassification to earnings	0		1,115		-2,264
Other Comprehensive Income (Loss), Minimum Pension Liability Net Adjustment, before Tax	706		1,239		771
Other Comprehensive Income (Loss), Minimum Pension Liability, Tax	-3,460		1,522		-1,439
Pension liability adjustment	($5,896)	[1]	$2,483	[1]	($2,470)	[1]

[1]	(2)B Refer to Note 1 - Summary of Significant Accounting Policies for detail of the pension amount reclassified to general and administrative expense on the Companybs consolidated statements of operations.

Accounts_Receivable_and_Accoun2

Accounts Receivable and Accounts Payable and Accrued Expenses Accounts Receivable (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	$322,630	$318,371
Accrued oil, gas, and NGL production revenue
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	180,250	228,169
Amounts due From Joint Interest Owner
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	58,347	37,517
Derivative Settlement Receivable [Member]
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	39,811	770
State severance tax refunds
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	24,394	29,213
Other
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	$19,828	$22,702

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, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts Payable and Accrued Expenses
Capital Expenditures Incurred but Not yet Paid	$357,200	$217,800	$262,800
Accounts payable and accrued expenses	640,684	606,751
Accrued Drilling Costs
Accounts Payable and Accrued Expenses
Capital Expenditures Incurred but Not yet Paid	357,156	217,820
Revenue and Severence Taxes Payable
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses	63,779	87,852
Accrued Lease Operating Expense
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses	34,822	29,296
Accrued property taxes
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses	15,059	10,401
Joint Owner Advances
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses	152	96,636
Accrued Compensation Costs
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses	56,279	71,466
Accrued interest
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses	40,786	40,027
Other
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses	$72,651	$53,253

Divestitures_and_Assets_Held_f2

Divestitures and Assets Held for Sale (Details) (USD $)	12 Months Ended
Divestitures and Assets Held for Sale (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 15, 2014	Sep. 24, 2014
Business Acquisition [Line Items]
Proved Oil and Gas Property, Successful Effort Method	$7,348,436,000	$5,637,462,000
Unproved Oil and Gas Property, Successful Effort Method	532,498,000	271,100,000
Asset Retirement Obligations, Noncurrent	-120,867,000	-118,692,000
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]
Cash received on divestiture of non-strategic assets	43,858,000	424,849,000	55,375,000
Estimated gain on divestiture of assets	646,000	27,974,000	-27,018,000
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down	27,600,000
Gain (Loss) on Sale of Proved Property	-646,000	-27,974,000	27,018,000
Assets Held-for-sale, Current
Reasonably certain period within which sale will take place (in years)	1
Oil and gas properties held for sale	17,891,000	19,072,000
Asset Retirement Obligations Assets Held-for-sale Noncurrent	438,000
Oil and Gas Properties
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]
Depletion, depreciation, amortization, and asset retirement obligation liability accretion			1,700,000
Gain (Loss) on Sale of Proved Property			33,900,000
Gooseneck Prospect Acquisition [Member]
Business Acquisition [Line Items]
Net acres acquired					61,000
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds				84,836,000	325,230,000
Gooseneck Prospect Acquisition [Member] \| Fair Value, Measurements, Nonrecurring [Member]
Business Acquisition [Line Items]
Proved Oil and Gas Property, Successful Effort Method				54,360,000	203,493,000
Unproved Oil and Gas Property, Successful Effort Method				29,469,000	126,622,000
Oil and Gas Property, Successful Effort Method, Net				83,829,000	330,115,000
Working Capital Acquired				2,625,000	2,772,000
Asset Retirement Obligations, Noncurrent				-1,618,000	-2,113,000
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds					325,230,000
Gooseneck Second Prospect Acquisition [Member] \| Fair Value, Measurements, Nonrecurring [Member]
Business Acquisition [Line Items]
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds				84,836,000
Rocky Mountain Acquisition [Domain]
Business Acquisition [Line Items]
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds	134,500,000
Leasehold Acres Consideration to Acquire Unproved Property	7,000
Rocky Mountain [Member]
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]
Cash received on divestiture of non-strategic assets	50,100,000
Estimated gain on divestiture of assets	26,900,000
Mid Continent Divestiture 2013 [Member]
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]
Cash received on divestiture of non-strategic assets		368,500,000
Estimated gain on divestiture of assets		25,300,000
Rocky Mountain Divestiture 2013 [Member]
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]
Cash received on divestiture of non-strategic assets		57,100,000
Estimated gain on divestiture of assets		13,200,000
Permian Divestiture 2013 [Member]
Disposal Group, Not Discontinued Operation, Disposal Disclosures [Abstract]
Cash received on divestiture of non-strategic assets		14,000,000
Estimated gain on divestiture of assets		-7,000,000
Mid Continent and Rocky Mountain Divestiture 2012 [Member]
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

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
Income Taxes (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
IRS Proposed R&D Tax Adjustment	$4,600,000
Excess tax benefit	0	0	0
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	0	0
Components of the provision for income taxes
Federal	0	0	0
State	868,000	2,121,000	370,000
Deferred portion of income tax expense (benefit)	397,780,000	105,555,000	-29,638,000
Income tax (expense) benefit	398,648,000	107,676,000	-29,268,000
Effective tax rate (as a percent)	37.40%	38.60%	35.00%
Excess income tax benefit from the exercise of stock awards	0
Deferred Income Taxes [Abstract]
Deferred Tax Liabilities, Oil and Gas Properties	1,029,424,000	768,463,000
Deferred Tax Liabilities, Derivative asset	220,437,000	9,529,000
Deferred Tax Liabilities, Other	4,475,000	1,245,000
Deferred Tax Liabilities	1,254,336,000	779,237,000
Deferred Tax Assets, Federal and state tax net operating loss carryovers	184,447,000	91,788,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	16,763,000	18,820,000
Deferred Tax Assets, Stock compensation	126,700,000
Deferred Tax Assets, Other Long-term Liabilities	16,301,000	13,341,000
Deferred Tax Assets, Net Profits Plan Liability	9,414,000	20,913,000
Deferred Tax Assets, Gross	226,925,000	144,862,000
Deferred Tax Assets, Valuation Allowance	-7,246,000	-5,001,000
Deferred Tax Assets, Net	219,679,000	139,861,000
Deferred Tax Liabilities, Net	1,034,657,000	639,376,000
Less: current deferred income tax liabilities	-152,082,000	-172,000
Add: current deferred income tax assets	9,106,000	10,921,000
Deferred income taxes; Net, non-current	891,681,000	650,125,000
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	626,200,000
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	284,800,000
Deferred Tax Assets, Tax Credit Carryforwards, Research	3,500,000
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Federal statutory tax expense (benefit)	372,644,000	97,514,000	-29,231,000
State tax expense (benefit) (net of federal benefit)	21,350,000	9,400,000	-992,000
Research and development credit	0	0	-970,000
Change in valuation allowance	2,245,000	-314,000	1,524,000
Other	2,409,000	1,076,000	401,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Beginning Balance	2,358,000	2,278,000	1,961,000
Unrecognized Tax Benefits, Additions For Tax Positions Of Prior Years	140,000	80,000	317,000
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	-916,000	0	0
Unrecognized Tax Benefits, Ending Balance	1,582,000	2,358,000	2,278,000
Internal Revenue Service (IRS) [Member]
Deferred Income Taxes [Abstract]
Income Taxes Receivable, Current	4,734,000	4,630,000
State and Local Jurisdiction [Member]
Deferred Income Taxes [Abstract]
Income Taxes Receivable, Current	0	0
Taxes Payable, Current	25,000	1,460,000
Minimum [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Ending Balance	0
Maximum [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Ending Balance	$1,200,000

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)	12 Months Ended
Long-Term Debt (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Nov. 17, 2014	20-May-13	Jun. 29, 2012	Nov. 08, 2011	Feb. 07, 2011
Debt Instrument [Line Items]
Senior Notes	$2,200,000,000	$1,600,000,000
Debt Conversion, Converted Instrument, Amount			2,641,000
Interest Costs, Capitalized During Period	16,200,000	11,000,000	12,100,000
Senior Notes [Member]
Debt Instrument [Line Items]
6.625% Senior Notes, Due 2019 Face Value	350,000,000	350,000,000
6.50% Senior Notes, Due 2021 Face Value	350,000,000	350,000,000
6.125% Senior Notes, Due 2022	600,000,000	0
6.50% Senior Notes, Due 2023 Face Value	400,000,000	400,000,000
5% Senior Notes, Due 2024 Face Value	500,000,000	500,000,000
Senior Notes	2,200,000,000	1,600,000,000
Debt Instrument, Covenant Compliance, Dividends Excluded From Computation	6,500,000
Senior Notes [Member] \| 6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					600,000,000
Debt Instrument, Interest Rate, Stated Percentage					6.13%
Net proceeds from debt issuance	590,000,000
Deferred Finance Costs, Gross					10,000,000
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%
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)	106.13%
Debt Instrument, Call Feature	at a redemption price equal to 100 percent of the principal amount of the 2022 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date.B
Maximum Penalty as a Percentage of Face Value for Not Registering Senior Notes Within One Year of Issuance					1.00%
Senior Notes [Member] \| 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount						500,000,000
Debt Instrument, Interest Rate, Stated Percentage						5.00%
Net proceeds from debt issuance		490,200,000
Deferred Finance Costs, Gross						9,800,000
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%
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
Senior Notes [Member] \| 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							400,000,000
Debt Instrument, Interest Rate, Stated Percentage							6.50%
Net proceeds from debt issuance			392,100,000
Deferred Finance Costs, Gross							7,900,000
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%
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)	106.50%
Debt Instrument, Call Feature	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.
Senior Notes [Member] \| 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount								350,000,000
Debt Instrument, Interest Rate, Stated Percentage								6.50%
Net proceeds from debt issuance				343,100,000
Deferred Finance Costs, Gross								6,900,000
Debt Instrument, Call Feature	redemption price equal to 100 percent of the principal amount, plus a specified make-whole premium and accrued and unpaid interest
Senior Notes [Member] \| 6.625% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount									350,000,000
Debt Instrument, Interest Rate, Stated Percentage									6.63%
Net proceeds from debt issuance				341,100,000
Deferred Finance Costs, Gross									8,900,000
Senior Notes [Member] \| 2015 [Member] \| 6.625% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	103.31%
Senior Notes [Member] \| 2016 [Member] \| 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	103.25%
Senior Notes [Member] \| 2016 [Member] \| 6.625% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	101.66%
Senior Notes [Member] \| 2017 [Member] \| 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	103.25%
Senior Notes [Member] \| 2017 [Member] \| 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	102.17%
Senior Notes [Member] \| 2018 [Member] \| 6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	103.06%
Senior Notes [Member] \| 2018 [Member] \| 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	102.50%
Senior Notes [Member] \| 2018 [Member] \| 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	102.17%
Senior Notes [Member] \| 2018 [Member] \| 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	101.08%
Senior Notes [Member] \| 2019 [Member] \| 6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	101.53%
Senior Notes [Member] \| 2019 [Member] \| 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	101.68%
Senior Notes [Member] \| 2019 [Member] \| 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	101.08%
Senior Notes [Member] \| 2020 [Member] \| 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	100.83%
Senior Notes [Member] \| 2020 and Thereafter [Member] \| 6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	100.00%
Senior Notes [Member] \| 2020 and Thereafter [Member] \| 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	100.00%
Senior Notes [Member] \| 2019 and Thereafter [Member] \| 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	100.00%
Senior Notes [Member] \| 2017 and Thereafter [Member] \| 6.625% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	100.00%
Senior Notes [Member] \| 2021 and Thereafter [Member] \| 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Early Debt Redemption, Redemption Price as a Percent of Face Amount	100.00%
Convertible Debt [Member] \| 3.50% Senior Convertible Notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.50%
Conversion of 3.50% Senior Convertible Notes to common stock, including income tax benefit of conversion (shares)			864,106
Debt Conversion, Converted Instrument, Amount			281,300,000
Repayments of Convertible Debt			$6,200,000

Longterm_Debt_Revolving_Credit

Long-term Debt Revolving Credit Facility (Details) (USD $)	12 Months Ended
Long-term Debt Revolving Credit Facility (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Dec. 10, 2014	Oct. 06, 2014	Sep. 06, 2013	Feb. 18, 2015
Line of Credit Facility [Line Items]
Long-term Line of Credit	166,000,000		$0
Line of Credit [Member]
Line of Credit Facility [Line Items]
Long-term Line of Credit	166,000,000		0
Letters of Credit Outstanding, Amount	808,000	[1]	808,000	[1]
Line of Credit Facility, Remaining Borrowing Capacity	1,333,192,000		1,299,192,000
Line of Credit [Member] \| Borrowing Base Utilization of 25 Percent [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.30%
Line of Credit [Member] \| Borrowing Base Utilization Of More Than 25 Percent But Less Than 50 Percent [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.30%
Line of Credit [Member] \| Borrowing Base Utilization Of More Than 50 Percent But Less Than 75 Percent [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.35%
Line of Credit [Member] \| Borrowing Base Utilization Of More Than 75 Percent But Less Than 90 Percent [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.38%
Line of Credit [Member] \| Borrowing Base Utilization Of More Than 90 Percent [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.38%
Line of Credit [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Deferred Finance Costs, Gross					3,400,000
Line of Credit Facility, Maximum Borrowing Capacity					2,500,000,000
Line of Credit Facility, Current Borrowing Capacity					1,500,000,000
Borrowing Base, Line of Credit						2,400,000,000	2,200,000,000
Percentage of Proved Oil and Gas Properties Secured for Credit Facility Borrowing	75.00%
Eurodollar [Member] \| Line of Credit [Member] \| Borrowing Base Utilization of 25 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Eurodollar [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 25 Percent But Less Than 50 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Eurodollar [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 50 Percent But Less Than 75 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Eurodollar [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 75 Percent But Less Than 90 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Eurodollar [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 90 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.25%
Eurodollar [Member] \| Line of Credit [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	London Interbank Offered Rate plus the applicable margin from the utilization table
Debt Instrument Variable Rate, Alternative Base Rate, And Swingline Loans [Member] \| Line of Credit [Member] \| Borrowing Base Utilization of 25 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.25%
Debt Instrument Variable Rate, Alternative Base Rate, And Swingline Loans [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 25 Percent But Less Than 50 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Debt Instrument Variable Rate, Alternative Base Rate, And Swingline Loans [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 50 Percent But Less Than 75 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.75%
Debt Instrument Variable Rate, Alternative Base Rate, And Swingline Loans [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 75 Percent But Less Than 90 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Debt Instrument Variable Rate, Alternative Base Rate, And Swingline Loans [Member] \| Line of Credit [Member] \| Borrowing Base Utilization Of More Than 90 Percent [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Debt Instrument Variable Rate, Alternative Base Rate, And Swingline Loans [Member] \| Line of Credit [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	Prime plus the applicable margin from the utilization table
Subsequent Event [Member] \| Line of Credit [Member]
Line of Credit Facility [Line Items]
Long-term Line of Credit								341,000,000
Letters of Credit Outstanding, Amount								808,000	[1]
Line of Credit Facility, Remaining Borrowing Capacity								$1,158,192,000

[1]	(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
Commitments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies
Operating Leases, Rent Expense	$6,500,000	$5,700,000	$5,400,000
Contractual Obligation, Due in Next Twelve Months	224,897,000
Contractual Obligation, Due in Second Year	147,896,000
Contractual Obligation, Due in Third Year	118,320,000
Contractual Obligation, Due in Fourth Year	128,866,000
Contractual Obligation, Due in Fifth Year	132,920,000
Contractual Obligation, Due after Fifth Year	383,619,000
Contractual Obligation	1,136,518,000
Drilling Rig Leasing Contracts
Commitments and Contingencies
Long-term Purchase Commitment, Amount	116,100,000
Early Termination Penalty For Rig Contract Cancellation	75,800,000
Gas gathering through-put commitments
Commitments and Contingencies
Long-term Purchase Commitment, Amount	939,400,000
Office Space Leases
Commitments and Contingencies
Long-term Purchase Commitment, Amount	69,300,000
Other miscellaneous contracts and leases
Commitments and Contingencies
Long-term Purchase Commitment, Amount	$11,700,000
Natural Gas [Member]
Commitments and Contingencies
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume	1,411,000
Crude Oil [Member]
Commitments and Contingencies
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume	48,000,000

Compensation_Plans_Stock_Based

Compensation Plans: Stock Based (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
	A		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	3,600,000
Impact outright issuance of one share has on number of available shares	1
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	$0		$0
Employee Service Share-bassed Compensation, Cash Received from Exercise, All Grant Types	4,000,000		3,200,000		3,000,000
Director Shares
Minimum Service Requirement for Immediate Vesting of Granted Shares	5
Shares Issued to the Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,600,000		1,400,000		1,300,000
Director Shares
Vesting Period for Director Share Grants	1
Stock issued from treasury to non-employee directors (in shares)	27,677		28,169		30,486
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	433,660	[1]	572,469	[1]	669,308	[1]	885,894	[1]
Maximum Impact of issuance of one performance share award on available shares under the equity incentive plan	2
Unrecognized stock based compensation expense	19,800,000
Fair value of PSUs/RSUs Granted in Period	19,200,000		17,600,000		16,400,000
PSU/RSU Vesting Increment	0.33		0.33		0.33
Fair value of PSUs/RSUs Vested in Period	13,400,000		20,700,000		22,100,000
Multiplier Applied to PSU Awards at Settlement	0.55		1.725		2
Shares Issued in Period	85,121		387,461		812,562
Shares held for settlement of income and payroll tax obligations (in shares)	45,042		200,050		406,866
Stock-based compensation expense	16,000,000		16,800,000		18,200,000
Weighted Average Grant Date Fair Value
Non-vested outstanding at the beginning of the period (in dollars per share)	$66.07	[1]	$63.91	[1]	$57.52	[1]
Granted (in dollars per share)	$94.66	[1]	$64.13	[1]	$51.98	[1]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	202,404	[1]	274,831	[1]	314,853	[1]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	206,830	[1]	345,005	[1]	493,679	[1]
Vested (in dollars per share)	$64.79	[1]	$60.06	[1]	$44.72	[1]
Forfeited (in dollars per share)	$86.72	[1]	$69.74	[1]	$65.35	[1]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	134,383	[1]	26,665	[1]	37,760	[1]
Non-vested outstanding at the end of the period (in dollars per share)	$73.63	[1]	$66.07	[1]	$63.91	[1]
Multiplier assumed	1
Performance measurement period	3
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	515,724		580,431		496,244		308,877
Unrecognized stock based compensation expense	22,500,000
Fair value of PSUs/RSUs Granted in Period	19,700,000		19,800,000		18,800,000
PSU/RSU Vesting Increment	0.33		0.33		0.33
Fair value of PSUs/RSUs Vested in Period	14,700,000		10,300,000		5,400,000
Shares Issued in Period	253,031		207,378		166,670
Shares held for settlement of income and payroll tax obligations (in shares)	81,434		67,987		49,857
Stock-based compensation expense	$13,900,000		$13,100,000		$9,800,000
Weighted Average Grant Date Fair Value
Non-vested outstanding at the beginning of the period (in dollars per share)	$57.05		$51.81		$44.33
Granted (in dollars per share)	$83.98		$60.01		$49.47
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	234,560		329,939		379,332
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	253,031		207,376		166,672
Vested (in dollars per share)	$58.19		$49.73		$32.72
Forfeited (in dollars per share)	$62.06		$54.37		$51.06
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	46,236		38,376		25,293
Non-vested outstanding at the end of the period (in dollars per share)	$68.29		$57.05		$51.81
Minimum PSU Multiplier [Member] \| Performance Shares [Member]
Weighted Average Grant Date Fair Value
Common stock awards vesting multiplier, low end of range	0.00%
Maximum PSU Multiplier [Member] \| Performance Shares [Member]
Weighted Average Grant Date Fair Value
Common stock awards vesting multiplier, low end of range	200.00%

[1]	(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) (Restricted Stock Units (RSUs) [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock Units (RSUs) [Member]
Compensation plans
Stock-based compensation expense	$13,900,000	$13,100,000	$9,800,000
Unrecognized stock based compensation expense	22,500,000
Fair value of PSUs/RSUs Granted in Period	19,700,000	19,800,000	18,800,000
Fair value of PSUs/RSUs Vested in Period	$14,700,000	$10,300,000	$5,400,000
Shares Issued in Period	253,031	207,378	166,670
Stock issued for settlement, RSU, net of tax (in shares)	171,597	139,391	116,813
Shares held for settlement of income and payroll tax obligations (in shares)	81,434	67,987	49,857
Number of Shares Represented by Each RSU	1
RSU Vesting Increment	0.33	0.33	0.33
RSUs
Non-vested at the beginning of the period (in shares)	580,431	496,244	308,877
Granted (in shares)	234,560	329,939	379,332
Vested (in shares)	-253,031	-207,376	-166,672
Forfeited (in shares)	-46,236	-38,376	-25,293
Non-vested at the end of the period (in shares)	515,724	580,431	496,244
Weighted- Average Grant-Date Fair Value
Non-vested outstanding at the beginning of the period (in dollars per share)	$57.05	$51.81	$44.33
Granted (in dollars per share)	$83.98	$60.01	$49.47
Vested (in dollars per share)	$58.19	$49.73	$32.72
Forfeited (in dollars per share)	$62.06	$54.37	$51.06
Non-vested outstanding at the end of the period (in dollars per share)	$68.29	$57.05	$51.81

Compensation_Plans_Stock_Optio

Compensation Plans Stock Option Grants Under the Equity Incentive Compensation Plan (Details) (Employee Stock Option [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Stock Option [Member]
Compensation plans
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$0
Shares
Outstanding, start of year	39,088	267,846	508,214
Exercised	-39,088	-228,758	-240,368
Forfeited	0	0	0
Outstanding, end of year	0	39,088	267,846
Vested and exercisable at end of year	0	39,088	267,846
Weighted Average Exercise Price
Outstanding, start of year (in dollars per share)	$20.87	$14.95	$13.86
Exercised (in dollars per share)	$20.87	$13.92	$12.65
Forfeited (in dollars per share)	$0	$0	$0
Outstanding, end of year (in dollars per share)	$0	$20.87	$14.95
Vested and exercisable at end of year (in dollars per share)	$0	$20.87	$14.95
Aggregate Intrinsic Value
Exercised	1,993,726	12,326,994	11,842,575
Outstanding	0	2,432,837	9,983,177
Vested and exercisable at end of year	$0	$2,432,837	$9,983,177

Compensation_Plans_Employee_St

Compensation Plans Employee Stock Purchase Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation plans
Number of shares available for grant	3,600,000
Proceeds from sale of common stock	$4,877,000	$6,858,000	$5,816,000
Employee Stock [Member]
Compensation plans
Maximum employee subscription rate	15.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription	25,000
Percent of offering date price paid	85.00%
Number of shares available for grant	1,100,000
Issuance of common stock under Employee Stock Purchase Plan (in shares)	83,136	77,427	66,485
Proceeds from sale of common stock	4,100,000	3,700,000	2,800,000
Risk free interest rate	0.10%	0.10%	0.10%
Dividend yield	0.10%	0.20%	0.20%
Volatility factor of the expected market price of the Company's common stock	33.00%	41.10%	47.80%
Expected life (in years)	6 months	6 months	6 months
Stock-based compensation expense	$1,100,000	$1,100,000	$948,000

Compensation_Plans_Non_StockBa

Compensation Plans Non Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Bonus Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Accrued Cash Bonus Plan Expense	$37,800,000	$41,800,000	$16,300,000
Non-qualified Deferred Compensation Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Base Salary Minimum Deferral Percentage	0.00%
Base Salary Maximum Deferral Percentage	50.00%
Cash Bonus Minimum Deferral Percentage	0.00%
Cash Bonus Maximum Deferral Percentage	100.00%
Cash Retainer Minimum Deferral Percentage	0.00%
Cash Retainer Maximum Deferral Percentage	100.00%
Company Percentage Contribution of Employee Deferred Amount	100.00%
Company Percentage Contribution Limit of Employee Deferred Amount	6.00%
Employee Vesting Percentage in Company Contribution After Two Years	40.00%
Employee Vesting Percentage in Company Contribution Year Three and Each Year Thereafter	20.00%
Distribution Option Minimum Years	1
Distribution Option Maximum Years	10
Net Profits Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Minimum Percentage of Oil and Gas Wells, 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 To	20.00%
Percentage of Oil and Gas Wells Costs Recovered for Additional Payment Employees from Net Profit Plan	200.00%
Cash Payments Made or Accrued under Profit Sharing Plan Allocated to General and Administrative Expense	8,326,000	13,734,000	15,565,000
Cash Payments Made or Accrued under Profit Sharing Plan Allocated to Oil and Gas Exploration Expense	690,000	1,310,000	1,751,000
Total Cash Payments, Made or Accrued under Profit Sharing Plan	9,016,000	15,044,000	17,316,000
Cash Payments Made or Accrued under Profit Sharing Plan Related to Divested Property	8,300,000	10,300,000	2,300,000
401-K Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	60.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$6,400,000	$4,200,000	$3,500,000

Pension_Benefits_Details

Pension Benefits (Details) (USD $)	12 Months Ended
Pension Benefits (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation Beginning of Year	$43,285,000		$40,237,000
Defined Benefit Plan, Service Cost	6,335,000		6,291,000		4,934,000
Defined Benefit Plan, Interest Cost	2,191,000		1,627,000		1,374,000
Defined Benefit Plan, Amendments	0		0
Defined Benefit Plan, Actuarial Gain (Loss)	8,821,000		-1,577,000
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Actuarial Gain (Loss), before Tax	-10,062,000		2,766,000		-4,680,000
Defined Benefit Plan, Benefits Paid	-2,765,000		-3,293,000		-1,000,000
Defined Benefit Plan, Benefit Obligation End of Year	57,867,000		43,285,000		40,237,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	24,658,000		20,254,000
Defined Benefit Plan, Actual Return on Plan Assets	737,000		2,726,000
Defined Benefit Plan, Employer Contribution	5,310,000		4,971,000		5,400,000
Defined Benefit Plan, Fair Value of Plan Assets End of Year	27,940,000		24,658,000		20,254,000
Defined Benefit Plan, Funded Status of Plan	-29,927,000		-18,627,000
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Defined Benefit Plan, Benefit Obligation End of Year	57,867,000		43,285,000		40,237,000
Defined Benefit Plan, Accumulated Benefit Obligation	43,205,000		32,396,000
Defined Benefit Plan, Fair Value of Plan Assets Beginning of Year	-27,940,000		-24,658,000		-20,254,000
Defined Benefit Plan, Accumulated Unfunded Benefit Obligation	15,265,000		7,738,000
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	17,812,000		8,439,000
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	118,000		136,000
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	17,930,000		8,575,000
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Arising During Period, before Tax	0		0		0
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		-17,000
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net (Gain) Loss Recognized in Net Periodic Benefit Cost, Net of Tax	-689,000		-1,222,000		-754,000
Total Other Comprehensive Income (Loss)	-9,356,000		4,005,000		-3,909,000
Components of Net Periodic Benefit Costs for Both Pension Plans
Defined Benefit Plan, Service Cost	6,335,000		6,291,000		4,934,000
Defined Benefit Plan, Interest Cost	2,191,000		1,627,000		1,374,000
Defined Benefit Plan, Expected Return on Plan Assets	-1,978,000		-1,538,000		-1,165,000
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	17,000		17,000		17,000
Defined Benefit Plan, Amortization of Gains (Losses)	689,000		1,222,000		754,000
Defined Benefit Plan, Net Periodic Benefit Cost	7,254,000		7,619,000		5,914,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.30%		5.00%		3.90%
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	5.00%		3.90%		4.70%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	7.50%	[1]	7.50%	[1]	7.50%	[1]
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	3,006,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	3,046,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	3,921,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	4,558,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	5,204,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	38,427,000
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	1,200,000
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	5,800,000
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	10,744,000
Defined Benefit Plan, Fair Value of Plan Assets End of Year	11,067,000
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	($11,067,000)
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	42.00%
Defined Benefit Plan, Asset Allocation	39.60%		43.60%

[1]	(1)There is no assumed expected return on plan assets for the Nonqualified Pension Plan because there are no plan assets in the Nonqualified Pension Plan.

Pension_Benefits_Fair_Value_of

Pension Benefits Fair Value of Plan Assets in Heirarchy (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$4,864		$3,421		$2,384
Defined Benefit Plan, Fair Value of Plan Assets	27,940		24,658		20,254
Defined Benefit Plan, Asset Allocation	100.00%		100.00%
Defined Benefit Plan, Target Plan Asset Allocations	100.00%
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	19,908		18,098
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	3,168		3,139
Level 3
Defined Benefit Plan, Fair Value of Plan Assets	4,864		3,421
investment Purchases [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	1,232		742
Investment Income [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	144		161
Unrealized Investment Gain [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	67		134
Cash And Money Market Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Defined Benefit Plan, Asset Allocation	0.00%		0.00%
Cash And Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Cash And Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Cash And Money Market Funds [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Domestic Equity Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets	7,569	[1]	7,371	[1]
Defined Benefit Plan, Asset Allocation	27.10%	[1]	29.90%	[1]
Domestic Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	5,550	[1]	4,888	[1]
Domestic Equity Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	2,019	[1]	2,483	[1]
Domestic Equity Securities [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0	[1]	0	[1]
International Equity Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets	3,498	[2]	3,373	[2]
Defined Benefit Plan, Asset Allocation	12.50%	[2]	13.70%	[2]
International Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	3,498	[2]	3,373	[2]
International Equity Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
International Equity Securities [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Equity Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets	11,067		10,744
Defined Benefit Plan, Asset Allocation	39.60%		43.60%
Defined Benefit Plan, Target Plan Asset Allocations	42.00%
Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	9,048		8,261
Equity Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	2,019		2,483
Equity Securities [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0		0
High-yield Bonds [Member]
Defined Benefit Plan, Fair Value of Plan Assets	797	[3]	1,448	[3]
Defined Benefit Plan, Asset Allocation	2.90%	[3]	5.90%	[3]
High-yield Bonds [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	797	[3]	1,448	[3]
High-yield Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[3]	0	[3]
High-yield Bonds [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0	[3]	0	[3]
Fixed Income Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets	6,247	[4]	5,006	[4]
Defined Benefit Plan, Asset Allocation	22.40%	[4]	20.30%	[4]
Fixed Income Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	6,247	[4]	5,006	[4]
Fixed Income Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[4]	0	[4]
Fixed Income Funds [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0	[4]	0	[4]
Floating Rate Corporate Debt [Member]
Defined Benefit Plan, Fair Value of Plan Assets	2,413	[5]	1,483	[5]
Defined Benefit Plan, Asset Allocation	8.60%	[5]	6.00%	[5]
Floating Rate Corporate Debt [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	2,413	[5]	1,483	[5]
Floating Rate Corporate Debt [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[5]	0	[5]
Floating Rate Corporate Debt [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0	[5]	0	[5]
Debt Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets	9,457		7,937
Defined Benefit Plan, Asset Allocation	33.90%		32.20%
Defined Benefit Plan, Target Plan Asset Allocations	35.00%
Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	9,457		7,937
Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Debt Securities [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Commodities Investment [Member]
Defined Benefit Plan, Fair Value of Plan Assets	810	[6]	945	[6]
Defined Benefit Plan, Asset Allocation	2.90%	[6]	3.80%	[6]
Commodities Investment [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	810	[6]	945	[6]
Commodities Investment [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[6]	0	[6]
Commodities Investment [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0	[6]	0	[6]
Real Estate Investment [Member]
Defined Benefit Plan, Fair Value of Plan Assets	1,327	[7]	859	[7]
Defined Benefit Plan, Asset Allocation	4.70%	[7]	3.50%	[7]
Real Estate Investment [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[7]	0	[7]
Real Estate Investment [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[7]	0	[7]
Real Estate Investment [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	1,327	[7]	859	[7]
Hedge Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets	4,130	[8]	3,517	[8]
Defined Benefit Plan, Asset Allocation	14.80%	[8]	14.30%	[8]
Hedge Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	593	[8]	955	[8]
Hedge Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[8]	0	[8]
Hedge Funds [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	3,537	[8]	2,562	[8]
Collective Investment Trust [Member]
Defined Benefit Plan, Fair Value of Plan Assets	1,149	[9]	656	[9]
Defined Benefit Plan, Asset Allocation	4.10%	[9]	2.60%	[9]
Collective Investment Trust [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	[9]	0	[9]
Collective Investment Trust [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	1,149	[9]	656	[9]
Collective Investment Trust [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	0	[9]	0	[9]
Other Investments [Member]
Defined Benefit Plan, Fair Value of Plan Assets	7,416		5,977
Other Investments [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	1,403		1,900
Other Investments [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	1,149		656
Other Investments [Member] \| Level 3
Defined Benefit Plan, Fair Value of Plan Assets	$4,864		$3,421
Other than Securities Investment [Member]
Defined Benefit Plan, Asset Allocation	26.50%		24.20%
Defined Benefit Plan, Target Plan Asset Allocations	23.00%

[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. 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
Asset Retirement Obligations (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligations [Line Items]
Asset Retirement Obligations Assets Held-for-sale Noncurrent	$438,000
Asset Retirement Obligation, Current	1,300,000	2,500,000
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation: Beginning of Year	121,186,000	120,518,000
Asset Retirement Obligation, Liabilities Incurred	13,506,000	18,682,000
Asset Retirement Obligation, Liabilities Settled	-11,372,000	-33,129,000
Asset Retirement Obligation, Accretion Expense	6,090,000	5,997,000
Asset Retirement Obligation, Revision of Estimate	-7,286,000	9,118,000
Asset Retirement Obligation: End of Year	$122,124,000	$121,186,000
Minimum [Member]
Asset Retirement Obligations [Line Items]
Fair Value Assumptions, Risk Free Interest Rate	5.50%
Maximum [Member]
Asset Retirement Obligations [Line Items]
Fair Value Assumptions, Risk Free Interest Rate	12.00%

Derivative_Financial_Instrumen3

Derivative Financial Instruments (Details)	Dec. 31, 2014
Derivative Financial Instruments (Details)	bbl
Crude Oil [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	14,700,000
Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	230,800,000
Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	781,000
IF El Paso Permian [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	3.00%
Index percent of natural gas collars	4.00%
IF HSC [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	82.00%
Index percent of natural gas collars	80.00%
IF NGPL TXOK [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	1.00%
IF NNG Ventura [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	3.00%
Index percent of natural gas collars	8.00%
IF Enable East [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	11.00%
Index percent of natural gas collars	8.00%
OPIS Natural Gasoline Mt Belv Non TET [Member]
Derivative Financial Instruments
Index percent of NGL fixed swaps	28.00%
OPIS Propane Mt Belv TET [Member]
Derivative Financial Instruments
Index percent of NGL fixed swaps	72.00%
Swap [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	11,311,000
Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	217,763,000
Swap [Member] \| Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	781,000
Collar [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	3,366,000
Collar [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	13,002,000
First Quarter of 2015 [Member] \| Swap [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Contract Price	91.96
Portion of Future Oil and Gas Production Being Hedged	1,711,000
First Quarter of 2015 [Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	23,548,000
Weighted- Average Contract Price	4.22
First Quarter of 2015 [Member] \| Swap [Member] \| Natural Gas Liquids [Member]
Derivative Financial Instruments
Weighted- Average Contract Price	55.42
Portion of Future Oil and Gas Production Being Hedged	781,000
First Quarter of 2015 [Member] \| Collar [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Floor Price	85
Weighted- Average Ceiling Price	99.53
Portion of Future Oil and Gas Production Being Hedged	882,000
First Quarter of 2015 [Member] \| Collar [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	2,524,000
Weighted- Average Floor Price	4
Weighted- Average Ceiling Price	4.3
Second Quarter of 2015 [Member] \| Swap [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Contract Price	91.26
Portion of Future Oil and Gas Production Being Hedged	1,639,000
Second Quarter of 2015 [Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	15,985,000
Weighted- Average Contract Price	3.9
Second Quarter of 2015 [Member] \| Collar [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Floor Price	85
Weighted- Average Ceiling Price	94.06
Portion of Future Oil and Gas Production Being Hedged	709,000
Second Quarter of 2015 [Member] \| Collar [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	2,297,000
Weighted- Average Floor Price	4
Weighted- Average Ceiling Price	4.3
Third Quarter of 2015 [Member] \| Swap [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Contract Price	90.78
Portion of Future Oil and Gas Production Being Hedged	1,254,000
Third Quarter of 2015 [Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	14,950,000
Weighted- Average Contract Price	4.03
Third Quarter of 2015 [Member] \| Collar [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Floor Price	85
Weighted- Average Ceiling Price	91.25
Portion of Future Oil and Gas Production Being Hedged	906,000
Third Quarter of 2015 [Member] \| Collar [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	2,005,000
Weighted- Average Floor Price	4
Weighted- Average Ceiling Price	4.3
Fourth Quarter of 2015 Member] \| Swap [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Contract Price	90.15
Portion of Future Oil and Gas Production Being Hedged	1,137,000
Fourth Quarter of 2015 Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	13,570,000
Weighted- Average Contract Price	4.02
Fourth Quarter of 2015 Member] \| Collar [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Floor Price	85
Weighted- Average Ceiling Price	92.19
Portion of Future Oil and Gas Production Being Hedged	869,000
Fourth Quarter of 2015 Member] \| Collar [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	6,176,000
Weighted- Average Floor Price	3.97
Weighted- Average Ceiling Price	4.3
2016 [Member] \| Swap [Member] \| Crude Oil [Member]
Derivative Financial Instruments
Weighted- Average Contract Price	88.01
Portion of Future Oil and Gas Production Being Hedged	5,570,000
2016 [Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	48,896,000
Weighted- Average Contract Price	4.12
2017 [Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	37,414,000
Weighted- Average Contract Price	4.16
2018 [Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	35,241,000
Weighted- Average Contract Price	4.21
2019 [Member] \| Swap [Member] \| Natural Gas [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	28,159,000
Weighted- Average Contract Price	4.28

Derivative_Financial_Instrumen4

Derivative Financial Instruments Fair Value (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
Fair value of derivative assets and liabilities
Derivative, Fair Value, Net	$592,100,000		$21,500,000
Derivative Assets, Current	402,668,000		21,559,000
Derivative Liabilities, Current	0		26,380,000
Derivative Assets, Noncurrent	189,540,000		30,951,000
Derivative Liabilities, Noncurrent	70,000		4,640,000
Derivative Asset, Fair Value, Gross Asset	592,208,000		52,510,000
Derivative Liability, Fair Value, Gross Liability	-70,000		-31,020,000
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	70,000		30,652,000
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	70,000		30,652,000
Derivative Asset, Fair Value, Amount Offset Against Collateral, Net	592,138,000		21,858,000
Derivative Liability, Fair Value, Amount Offset Against Collateral, Net	0		-368,000
Not Designated as Hedging Instrument [Member]
Fair value of derivative assets and liabilities
Derivative Assets, Current	402,668,000		21,559,000
Derivative Liabilities, Current	0		26,380,000
Derivative Assets, Noncurrent	189,540,000		30,951,000
Derivative Liabilities, Noncurrent	70,000		4,640,000
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Not Designated as Hedging Instrument [Member]
Fair value of derivative assets and liabilities
Derivative Asset, Fair Value, Gross Asset	592,208,000	[1]	52,510,000	[1]
Derivative Liability, Fair Value, Gross Liability	$70,000	[1]	$31,020,000	[1]

[1]	(1) This represents a financial asset or liability that is measured at fair value on a recurring basis.

Derivative_Financial_Instrumen5

Derivative Financial Instruments Gains and Losses (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Unrealized and realized gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivatives Settlement Adjustment	$41,000,000
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	12,615,000	[1]	22,062,000	[1]	44,264,000	[1]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	583,264,000	[2]	3,080,000	[2]	55,630,000	[2]
Amount reclassified from AOCIL	0		1,115,000		-2,264,000
Gain (Loss) on Hedging Activity			-1,800,000		3,900,000
Crude oil
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	28,410,000		-15,161,000		-11,893,000
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	457,082,000		-14,665,000		20,088,000
Natural Gas [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	-26,706,000		30,338,000		47,270,000
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	93,267,000		14,053,000		15,493,000
Natural Gas Liquids [Member]
Derivative, (Gain) Loss on Derivative, Net [Abstract]
Derivative Settlement Gain (Loss)	10,911,000		6,885,000		8,887,000
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$32,915,000		$3,692,000		$20,049,000

[1]	(1)B Total derivative settlement gain is reported in the derivative cash settlements line item on the accompanying statements of cash flows within net cash provided by operating activities with the change in accrued settlements between years being reported in change in accounts receivable and change in accounts payable and accrued expenses line items. Total derivative settlement gains are adjusted by a $41.0 million decrease attributable to the change in current assets and liabilities at December 31, 2014.
[2]	(2)B Total derivative gain is reported in the derivative gain line item on the accompanying statements of cash flows within net cash provided by operating activities.

Derivative_Financial_Instrumen6

Derivative Financial Instruments Credit Facility and Derivative Counterparties (Details) (Line of Credit [Member])	Dec. 31, 2014
Line of Credit [Member]
Line of Credit Facility [Line Items]
Percentage of Proved Oil and Gas Properties Secured for Credit Facility Borrowing	75.00%

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Assets:
Derivatives	$592,208		$52,510
Proved oil and gas properties	7,348,436		5,637,462
Unproved Oil and Gas Property, Successful Effort Method	532,498		271,100
Oil and gas properties held for sale	17,891		19,072
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	-70		-31,020
Net Profits Plan liability	27,136		56,985
Fair Value, Measurements, Recurring [Member] \| Level 1
Liabilities [Abstract]
Net Profits Plan liability	0	[1]	0	[1]
Fair Value, Measurements, Recurring [Member] \| Level 1 \| Not Designated as Hedging Instrument [Member]
Assets:
Derivatives	0	[1]	0	[1]
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	[1]	0	[1]
Fair Value, Measurements, Recurring [Member] \| Level 2
Liabilities [Abstract]
Net Profits Plan liability	0	[1]	0	[1]
Fair Value, Measurements, Recurring [Member] \| Level 2 \| Not Designated as Hedging Instrument [Member]
Assets:
Derivatives	592,208	[1]	52,510	[1]
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	70	[1]	31,020	[1]
Fair Value, Measurements, Recurring [Member] \| Level 3
Liabilities [Abstract]
Net Profits Plan liability	27,136	[1]	56,985	[1]
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Not Designated as Hedging Instrument [Member]
Assets:
Derivatives	0	[1]	0	[1]
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	[1]	0	[1]
Fair Value, Measurements, Nonrecurring [Member] \| Level 1
Assets:
Proved oil and gas properties	0	[2]	0	[2]
Unproved Oil and Gas Property, Successful Effort Method			0	[2]
Oil and gas properties held for sale	0	[2]	0	[2]
Fair Value, Measurements, Nonrecurring [Member] \| Level 2
Assets:
Proved oil and gas properties	0	[2]	0	[2]
Unproved Oil and Gas Property, Successful Effort Method			0	[2]
Oil and gas properties held for sale	0	[2]	0	[2]
Fair Value, Measurements, Nonrecurring [Member] \| Level 3
Assets:
Proved oil and gas properties	33,423	[2]	62,178	[2]
Unproved Oil and Gas Property, Successful Effort Method	0	[2]	3,280	[2]
Oil and gas properties held for sale	$17,891	[2]	$650	[2]

[1]	(1) This represents a financial asset or liability that is measured at fair value on a recurring basis.
[2]	(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 $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
	A		Dec. 31, 2013		Dec. 31, 2012
Proved Oil and Gas Properties
Discount rate used for fair value of oil and gas properties (as a percent)	12.00%
Number of periods used for price assumptions of strip prices of liabilities	5
Proved Oil and Gas Property, Successful Effort Method	$7,348,436,000		$5,637,462,000
Unproved Oil and Gas Property, Successful Effort Method	532,498,000		271,100,000
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%
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	2,600,000
Percent Change in Discount Rate for Sensitivity Analysis	1.00%
Sensitivity Analysis Change in Liability Due to Change in Discount Rate	1,100,000
Liability measured at fair value using Level 3 inputs
Net Profits Plan Liability: Beginning Balance	56,985,000		78,827,000		107,731,000
Net increase (decrease) in liability	-12,492,000	[1]	3,527,000	[1]	-9,251,000	[1]
Net settlements	-17,357,000	[1],[2]	-25,369,000	[1],[2]	-19,653,000	[1],[2]
Transfers in (out) of Level 3	0		0		0
Net Profits Plan Liability: Ending balance	27,136,000		56,985,000		78,827,000
Cash Payments Made or Accrued under Profit Sharing Plan Related to Divested Property	8,300,000		10,300,000		2,300,000
6.625% Senior Notes Due 2019 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value	350,018,000		374,290,000
6.50% Senior Notes Due 2021 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value	343,000,000		373,625,000
6.125% Senior Notes Due 2022 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value	556,500,000	[3]	0	[3]
6.50% Senior Notes Due 2023 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value	379,000,000		422,000,000
5% Senior Notes Due 2024 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value	$435,000,000		$475,315,000

[1]	(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]	(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 $8.3 million, $10.3 million, and $2.3 million relating to divestiture proceeds for the years ended DecemberB 31, 2014, 2013, and 2012, respectively.
[3]	(1) The 2022 Notes were issued on NovemberB 17, 2014.

Acquisition_and_Development_Ag1

Acquisition and Development Agreement and Carry and Earning Agreement (Details) (Mitsui E&P Texas LP, USD $)	Jun. 30, 2011
In Millions, unless otherwise specified	Jun. 30, 2011
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
Portion of Drilling and Completion Costs Not Carried by Acquirer	10.00%

Suspended_Well_Costs_Details

Suspended Well Costs (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized Exploratory Well Costs Beginning Balance	$34,527	$9,100	$18,600
Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves	43,589	34,527	9,100
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves	-33,340	-9,100	-5,865
Capitalized Exploratory Well Cost, Charged to Expense	-1,187	0	-12,735
Capitalized Exploratory Well Costs Ending Balance	43,589	34,527	9,100
Exploratory Well Costs Capitalized Greater than One Year	$0