SM Energy (SM) 10-Q 4 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	6 Months Ended
	Jun. 30, 2017	Jul. 26, 2017
Entity Information [Line Items]
Entity Registrant Name	SM Energy Co
Entity Central Index Key	893,538
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		111,623,367
Entity Current Reporting Status	Yes

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (in thousands, except share amounts) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 559,521		$ 9,372
Accounts receivable	105,713		151,950
Derivative asset	85,962		54,521
Prepaid expenses and other	18,121		8,799
Total current assets	769,317		224,642
Proved oil and gas properties	5,631,013		5,700,418
Less - accumulated depletion, depreciation, and amortization	(3,117,983)		(2,836,532)
Unproved oil and gas properties	2,418,984		2,471,947
Wells in progress	286,682		235,147
Oil and gas properties held for sale, net	18,739		372,621
Other property and equipment, net of accumulated depreciation of $47,738 and $42,882, respectively	108,976		137,753
Total property and equipment, net	5,346,411		6,081,354
Derivative asset	82,194		67,575
Other noncurrent assets	14,683		19,940
Total other noncurrent assets	96,877		87,515
Total Assets	6,212,605		6,393,511
Liabilities
Accounts payable and accrued expenses	311,476		299,708
Derivative liability	36,296		115,464
Total current liabilities	347,772		415,172
Revolving credit facility	0		0
Senior Notes, net of unamortized deferred financing costs	2,767,030		2,766,719
Senior Convertible Notes, net of unamortized discount and deferred financing costs	134,918		130,856
Asset retirement obligation	100,304		96,134
Asset retirement obligation associated with oil and gas properties held for sale	234		26,241
Deferred income taxes	245,506		315,672
Derivative liability	69,915		98,340
Other noncurrent liabilities	45,098		47,244
Total noncurrent liabilities	3,363,005		3,481,206
Commitments and contingencies (note 6)
Stockholders' equity:
Common stock, $0.01 par value - authorized: 200,000,000 shares; issued and outstanding; 111,453,476 and 111,257,500 shares, respectively	1,115		1,113
Additional paid-in capital	1,729,104		1,716,556
Retained earnings	786,608		794,020
Accumulated other comprehensive loss	(14,999)		(14,556)
Total stockholders' equity	2,501,828		2,497,133
Total Liabilities and Stockholders' Equity	$ 6,212,605		$ 6,393,511

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets Parenthetical - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Property, Plant and Equipment, Other, Accumulated Depreciation	$ 47,737
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	111,453,476	111,257,500
Common Stock, Shares, Outstanding	111,453,476	111,257,500

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) (in thousands, except per share amounts) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating revenues and other income:
Oil, gas, and NGL production revenue	$ 284,939	$ 291,142	$ 618,137	$ 502,965
Net gain (loss) on divestiture activity	(167,133)	50,046	(129,670)	(18,975)
Other operating revenues	2,915	626	4,992	900
Total operating revenues and other income	120,721	341,814	493,459	484,890
Operating expenses:
Oil, gas, and NGL production expense	124,376	148,591	262,422	293,134
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	153,232	211,020	291,044	425,227
Exploration	13,072	13,187	25,050	28,460
Impairment of proved properties	3,806	0	3,806	269,785
Abandonment and impairment of unproved properties	157	38	157	2,349
General and administrative	28,460	28,200	57,684	60,438
Net derivative (gain) loss	(55,189)	163,351	(169,963)	149,123
Other operating expenses	445	7,976	5,304	13,648
Total operating expenses	268,359	572,363	475,504	1,242,164
Income (loss) from operations	(147,638)	(230,549)	17,955	(757,274)
Non-operating income (expense):
Interest expense	(44,595)	(34,035)	(91,548)	(65,123)
Gain (loss) on extinguishment of debt	0	0	(35)	15,722
Other, net	1,265	5	1,600	11
Loss before income taxes	(190,968)	(264,579)	(72,028)	(806,664)
Income tax benefit	71,061	95,898	26,555	290,773
Net loss	$ (119,907)	$ (168,681)	$ (45,473)	$ (515,891)
Basic weighted-average common shares outstanding	111,277	68,102	111,274	68,090
Diluted weighted-average common shares outstanding	111,277	68,102	111,274	68,090
Basic net loss per common share	$ (1.08)	$ (2.48)	$ (0.41)	$ (7.58)
Diluted net loss per common share	(1.08)	(2.48)	(0.41)	(7.58)
Dividends per common share	$ 0	$ 0	$ 0.05	$ 0.05

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) (in thousands) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (119,907)	$ (168,681)	$ (45,473)	$ (515,891)
Other comprehensive income (loss), net of tax:
Pension liability adjustment	124	(269)	(443)	(505)
Total other comprehensive income (loss), net of tax	124	(269)	(443)	(505)
Total comprehensive loss	$ (119,783)	$ (168,950)	$ (45,916)	$ (516,396)

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (UNAUDITED) (in thousands, except share amounts) - 6 months ended Jun. 30, 2017 - USD ($) $ in Thousands		Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Dividends per common share		$ 0.05
Balances, Common Shares, Beginning at Dec. 31, 2016		111,257,500	111,257,500
Balances, Beginning at Dec. 31, 2016		$ 2,497,133	$ 1,113	$ 1,716,556	$ 794,020	$ (14,556)
Increase (Decrease) in Stockholders' Equity
Net loss		(45,473)			(45,473)
Other comprehensive loss		(443)				(443)
Cash dividends, $0.05 per share		5,563			5,563
Issuance of common stock under Employee Stock Purchase Plans (in shares)			123,678
Issuance of common stock under Employee Stock Purchase Plan		1,738	$ 1	1,737
Issuance of common stock upon vesting of restricted stock units, net of shares used for tax withholdings (in shares)			725
Issuance of common stock upon vesting of restricted stock units, net of shares used for tax withholdings		(11)	$ 0	(11)
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			71,573
Stock-based compensation expense		9,813	$ 1	9,812
Cumulative effect of accounting change	[1]	44,732		1,108	43,624
Other		$ (98)		(98)
Balances, Common Shares, Ending at Jun. 30, 2017		111,453,476	111,453,476
Balances, Ending at Jun. 30, 2017		$ 2,501,828	$ 1,115	$ 1,729,104	$ 786,608	$ (14,999)
[1]	(1) Refer to Note 2 - Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards.

CONDENSED CONSOLIDATED STATEME7

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (in thousands) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net loss	$ (45,473)	$ (515,891)
Adjustments to reconcile net loss to net cash provided by operating activities:
Net loss on divestiture activity	129,670	18,975
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	291,044	425,227
Impairment of proved properties	3,806	269,785
Abandonment and impairment of unproved properties	157	2,349
Stock-based compensation expense	9,813	13,915
Net derivative (gain) loss	(169,963)	149,123
Proceeds from Derivative Settlement	16,310	248,738
Amortization of debt discount and deferred financing costs	8,679	1,930
Non-cash (gain) loss on extinguishment of debt, net	22	(15,722)
Deferred income taxes	(30,790)	(291,014)
Plugging and abandonment	(1,609)	(2,716)
Other, net	2,267	2,517
Changes in current assets and liabilities:
Accounts receivable	46,993	(11,220)
Prepaid expenses and other	(9,321)	8,487
Accounts payable and accrued expenses	(8,973)	(61,727)
Accrued derivative settlements	(517)	14,117
Net cash provided by operating activities	242,115	256,873
Cash flows from investing activities:
Net proceeds from the sale of oil and gas properties	766,247	12,967
Capital expenditures	(366,743)	(345,570)
Acquisition of proved and unproved oil and gas properties	(88,140)	(17,751)
Other, net	3,000	(900)
Net cash provided by (used in) investing activities	314,364	(351,254)
Cash flows from financing activities:
Proceeds from credit facility	406,000	585,000
Repayment of credit facility	(406,000)	(456,500)
Debt issuance costs related to credit facility	0	(3,132)
Cash paid to repurchase Senior Notes	(2,344)	(29,904)
Net proceeds from sale of common stock	1,738	2,354
Dividends paid	(5,563)	(3,404)
Other, net	(161)	(33)
Net cash provided by (used in) financing activities	(6,330)	94,381
Net change in cash and cash equivalents	550,149	0
Cash and cash equivalents at beginning of period	9,372	18
Cash and cash equivalents at end of period	559,521	18
Supplemental schedule of additional cash flow information and non-cash activities:
Cash paid for interest, net of capitalized interest	(83,493)	(63,590)
Net cash (paid) refunded for income taxes	(8,220)	4,564
Changes in capital expenditures accruals and other	44,770	2,986
Fair value of properties exchanged	$ 279,750	$ 733

The Company and Business

The Company and Business	6 Months Ended
	Jun. 30, 2017
Company and Business Disclosure [Abstract]
The Company and Business	Note 1 - The Company and Business SM Energy Company, together with its consolidated subsidiaries (“SM Energy” or the “Company”), is an independent energy company engaged in the acquisition, exploration, development, and production of crude oil and condensate, natural gas, and natural gas liquids (also respectively referred to as “oil,” “gas,” and “NGLs” throughout this report) in onshore North America.

Basis of Presentation, Signific

Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards	6 Months Ended
	Jun. 30, 2017
Basis of Presentation and Significant Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	Note 2 - Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of SM Energy and its wholly-owned subsidiaries and have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and the instructions to Quarterly Report on Form 10-Q and Regulation S-X. These financial statements do not include all information and notes required by GAAP for annual financial statements. However, except as disclosed herein, there has been no material change in the information disclosed in the notes to consolidated financial statements included in SM Energy’s Annual Report on Form 10-K for the year ended December 31, 2016 (the “ 2016 Form 10-K”). In the opinion of management, all adjustments, consisting of normal recurring adjustments considered necessary for a fair presentation of interim financial information, have been included. Operating results for the periods presented are not necessarily indicative of expected results for the full year. In connection with the preparation of the Company’s unaudited condensed consolidated financial statements, the Company evaluated events subsequent to the balance sheet date of June 30, 2017 , and through the filing of this report. Certain prior period amounts have been reclassified to conform to the current presentation on the accompanying condensed consolidated financial statements. Significant Accounting Policies The significant accounting policies followed by the Company are set forth in Note 1 - Summary of Significant Accounting Policies to the Company’s consolidated financial statements in its 2016 Form 10-K, and are supplemented by the notes to the unaudited condensed consolidated financial statements in this report. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the 2016 Form 10-K. Recently Issued Accounting Standards Effective January 1, 2017, the Company adopted, using various transition methods, Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 is meant to simplify certain aspects of accounting for share-based arrangements, including income tax effects, accounting for forfeitures, and net share settlements. The Company adopted the various applicable amendments as summarized below: • On January 1, 2017, a $44.3 million cumulative-effect adjustment was made to retained earnings and a corresponding deferred tax asset was recorded for previously unrecognized excess tax benefits using a modified retrospective transition method. Additionally, going forward excess tax benefits will be presented in operating activities on the statement of cash flows. • Also on January 1, 2017, the Company elected to change its policy to account for forfeitures of share-based payment awards as they occur, rather than applying an estimated forfeiture rate. This change was made using a modified retrospective transition method and resulted in a net $0.7 million cumulative effect adjustment to retained earnings with a corresponding increase in additional paid-in capital and decrease in deferred tax assets. • As a result of adoption, excess tax benefits and deficiencies from share-based payments are expected to impact the Company’s effective tax rate between periods. Please refer to Note 4 - Income Taxes for additional discussion . In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”) . Under the new standard, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The FASB issued several amendments to the standard which provided additional implementation guidance and deferred the effective date of ASU 2014-09. While the Company does not expect net income (loss) or cash flows to be materially impacted, the Company is currently analyzing whether changes to total revenues and total expenses will be necessary to properly reflect revenue for certain pipeline gathering, transportation and gas processing agreements. The Company continues to evaluate the expected disclosure requirements, changes to relevant business practices, accounting policies, and control activities that will occur as a result of the adoption of this ASU, and has not yet developed estimates of the quantitative impact to its consolidated statements of financial position and operations. The Company plans to adopt the guidance using the modified retrospective method on the effective date of January 1, 2018. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) which requires lessees to recognize a right-of-use asset and a lease liability for virtually all leases currently classified as operating leases. The Company is currently analyzing the impact this standard has on the Company’s contract portfolio, including non-cancelable leases, drilling rig contracts, pipeline gathering, transportation and gas processing agreements, as well as other existing arrangements and is evaluating current accounting policies that will change as a result of this ASU. Appropriate systems, controls, and processes to support the recognition and disclosure of the new standard are also being evaluated. Based upon an initial assessment, adoption of this ASU is expected to result in: (i) an increase in assets and liabilities recorded, (ii) an increase in depreciation, depletion and amortization expense recorded, and (iii) an increase in interest expense recorded. The Company plans to adopt the guidance on the effective date of January 1, 2019. In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017-07”). This ASU requires presentation of service cost in the same line item(s) as other compensation costs arising from services rendered by employees during the period and presentation of the remaining components of net benefit cost in a separate line item, outside operating items. In addition, only the service cost component of net benefit cost is eligible for capitalization. The Company plans to adopt ASU 2017-07 on January 1, 2018, with retrospective application of the service cost component and the other components of net benefit cost in the consolidated statements of operations and prospective application for the capitalization of the service cost component of net benefit costs in assets. The Company is evaluating the impact of this ASU on its consolidated financial statements. Other than as disclosed above or in the 2016 Form 10-K, there are no other ASUs applicable to the Company that would have a material effect on the Company’s financial statements and related disclosures that have been issued but not yet adopted by the Company as of June 30, 2017 , and through the filing of this report.

Divestitures, Assets Held for S

Divestitures, Assets Held for Sale, and Acquisitions	6 Months Ended
	Jun. 30, 2017
Divestitures, Assets Held for Sale, and Acquisitions [Abstract]
Divestitures, Assets Held for Sale, and Acquisitions	Note 3 - Divestitures, Assets Held for Sale, and Acquisitions Divestitures On March 10, 2017 , the Company divested its outside-operated Eagle Ford shale assets, including its ownership interest in related midstream assets, for total cash received at closing, net of commissions (referred to throughout this report as “net divestiture proceeds”), of $747.4 million , and recorded an estimated net gain of $397.4 million for the six months ended June 30, 2017 . These assets were classified as held for sale as of December 31, 2016 . The following table presents income (loss) before income taxes from the outside-operated Eagle Ford shale assets sold for the three and six months ended June 30, 2017 , and 2016 . This divestiture is considered a disposal of a significant asset group. For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Income (loss) before income taxes (1) $ — $ 12,832 $ 24,324 $ (273,567 ) ____________________________________________ (1) Income (loss) before income taxes reflects oil, gas, and NGL production revenue, less oil, gas, and NGL production expense, and depletion, depreciation, amortization, and asset retirement obligation liability accretion. Additionally, income (loss) before income taxes included impairment of proved properties expense of approximately $269.6 million for the six months ended June 30, 2016 . During the second quarter of 2017, the Company divested a portion of its Divide County, North Dakota assets for net divestiture proceeds of $24.6 million . Also during the second quarter of 2017, the Company finalized the 2016 divestiture of its Raven/Bear Den assets resulting in a final net gain of $29.1 million . Assets Held for Sale Assets are classified as held for sale when the Company commits to a plan to sell the assets and there is reasonable certainty the sale will take place within one year. Upon classification as held for sale, long-lived assets are no longer depreciated or depleted, and a measurement for impairment is performed to identify and expense any excess of carrying value over fair value less estimated costs to sell. When assets no longer meet the criteria of assets held for sale, they are measured at the lower of the carrying value of the assets before being classified as held for sale, adjusted for any depletion, depreciation, and amortization expense that would have been recognized, or the fair value at the date they are reclassified to assets held for use. Any gain or loss recognized on assets held for sale or on assets held for sale that are subsequently reclassified to assets held for use is reflected in the net gain (loss) on divestiture activity line item in the accompanying condensed consolidated statements of operations (“accompanying statements of operations”). As of June 30, 2017 , there were $18.7 million of assets held for sale presented in the accompanying condensed consolidated balance sheets (“accompanying balance sheets”). During the second quarter of 2017 , the Company reclassified its retained Divide County assets previously held for sale to assets held for use due to the assets no longer being actively marketed as valuations in the sales process did not reach the Company’s expectations. A $359.6 million write-down was recorded on these assets in the first quarter of 2017 based on the estimated fair value less selling costs as of March 31, 2017. An additional $166.9 million write-down was recorded in the second quarter of 2017 based on market conditions that existed on the date the Company made its decision to retain these assets. For the first quarter of 2016, certain assets held for sale were written down by $68.3 million to reflect fair value less estimated costs to sell at March 31, 2016. During the second quarter of 2016, the Company estimated an increase in the fair value of certain of these previously impaired assets held for sale due to an increase in estimated selling prices, as evidenced by bid prices received from third parties, resulting in a $49.5 million gain recorded for the three months ended June 30, 2016 . Acquisitions During the first half of 2017, the Company acquired approximately 3,400 net acres of primarily unproved properties in the Midland Basin in multiple transactions totaling $72.3 million of cash consideration. Under authoritative accounting guidance, these transactions were considered asset acquisitions and the properties were recorded based on the fair value of the total consideration transferred on the acquisition date and transaction costs were capitalized as a component of the cost of the assets acquired. The Company finalized the 2016 acquisition of Midland Basin properties from Rock Oil Holdings, LLC (referred to as the “Rock Oil Acquisition”) during the first quarter of 2017 by paying an additional $7.4 million of cash consideration, resulting in total consideration of $998.4 million paid after final closing adjustments. Subsequent to June 30, 2017, the Company finalized the 2016 acquisition of Midland Basin properties from QStar LLC and RRP-QStar, LLC (referred to as the “QStar Acquisition”). The Company paid an additional $7.1 million of cash consideration during 2017, with the majority of this payment being made in the first quarter of 2017, resulting in total consideration of $1.6 billion after final closing adjustments. There were no material changes to the recorded basis of these proved and unproved properties acquired as a result of the final settlements. Also, during the first half of 2017, the Company completed several trades of properties, primarily unproved, in Howard and Martin Counties, Texas resulting in the Company acquiring approximately 6,550 net acres in exchange for approximately 5,700 net acres. These trades were recorded at carryover basis with no gain or loss recognized.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 4 - Income Taxes The income tax benefit recorded for the three and six months ended June 30, 2017 , and 2016 , differs from the amounts that would be provided by applying the statutory United States federal income tax rate to income or loss before income taxes primarily due to the effect of state income taxes, changes in valuation allowances, excess tax benefits and deficiencies from share-based payment awards, and accumulated impacts of other smaller permanent differences. The quarterly rate can also be affected by the proportional impacts of forecasted net income or loss as of each period end presented. The provision for income taxes for the three and six months ended June 30, 2017 , and 2016 , consisted of the following: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Current portion of income tax benefit (expense): Federal $ 4,607 $ — $ (2,832 ) $ — State 2,439 (77 ) (1,403 ) (241 ) Deferred portion of income tax benefit 64,015 95,975 30,790 291,014 Income tax benefit $ 71,061 $ 95,898 $ 26,555 $ 290,773 Effective tax rate 37.2 % 36.2 % 36.9 % 36.0 % On a year-to-date basis, a change in the Company’s effective tax rate between reporting periods will generally reflect differences in its estimated highest marginal state tax rate due to changes in the composition of income or loss from Company activities among multiple state tax jurisdictions. As a result of adopting ASU 2016-09 on January 1, 2017, excess tax benefits and deficiencies from share-based payment awards are expected to impact the Company’s effective tax rate between periods. As discussed in Note 7 - Compensation Plans , subsequent to June 30, 2017, the Company settled various RSU grants and the 2014 PSU grant. As a result of these share-based award settlements, the Company expects to record an excess tax deficiency in the third quarter of 2017. Cumulative effects of state tax rate changes are reflected in the period legislation is enacted. The change in the current portion of income tax benefit (expense) and the effective tax rate relates to the effect of anticipated utilization of carryover net operating losses, deferred tax expenses, and carryover tax credits. The Company is generally no longer subject to United States federal or state income tax examinations by tax authorities for years before 2013. Its 2003 to 2005 tax years have been reopened for net operating loss carryback claims and are currently under examination by the Internal Revenue Service.

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Long-term Debt [Text Block]	Note 5 - Long-Term Debt Credit Facility The Company’s Fifth Amended and Restated Credit Agreement, as amended (the “Credit Agreement”), provides for a maximum loan amount of $2.5 billion and has a maturity date of December 10, 2019 . On March 31, 2017 , the Company entered into a Ninth Amendment to the Credit Agreement (the “Ninth Amendment”) with its lenders. Pursuant to the Ninth Amendment, and as part of the regular, semi-annual borrowing base redetermination process, the borrowing base and aggregate lender commitments were reduced to $925 million . This expected reduction was primarily due to the sale of the Company’s outside-operated Eagle Ford shale assets in the first quarter of 2017 and the decrease in the value of the Company’s proved reserves at December 31, 2016. The borrowing base redetermination process considers the value of both the Company’s (a) proved oil and gas properties reflected in the Company’s most recent reserve report and (b) commodity derivative contracts, each as determined by the Company’s lender group. Additionally, the Ninth Amendment modified the Credit Agreement to allow the Company to enter into derivative contracts for an increased percentage of projected production volumes. As a result of the reduction to the Company’s borrowing base and aggregate lender commitments, the Company recorded approximately $1.1 million of expense related to the acceleration of unamortized deferred financing costs for the six months ended June 30, 2017 . The next scheduled redetermination date is October 1, 2017 . The Company must comply with certain financial and non-financial covenants under the terms of the Credit Agreement, including covenants limiting dividend payments and requiring the Company to maintain certain financial ratios, as defined by the Credit Agreement. Certain financial covenants under the Credit Agreement require, as of the last day of each of the Company’s fiscal quarters, the Company’s (a) ratio of senior secured debt to 12-month trailing adjusted EBITDAX to be not more than 2.75 to 1.0; (b) adjusted current ratio to be not less than 1.0 to 1.0; and (c) ratio of 12-month trailing adjusted EBITDAX to interest expense to be not less than 2.0 to 1.0. The Company was in compliance with all financial and non-financial covenants under the Credit Agreement as of June 30, 2017 , and through the filing of this report. Interest and commitment fees are accrued based on a borrowing base utilization grid set forth in the Credit Agreement and presented in Note 5 - Long-Term Debt to the Company’s consolidated financial statements in its 2016 Form 10-K. Eurodollar loans accrue interest at the London Interbank Offered Rate plus the applicable margin from the utilization table, and Alternate Base Rate and swingline loans accrue interest at the prime rate, plus the applicable margin from the utilization table. Commitment fees are accrued on the unused portion of the aggregate lender commitment amount and are included in interest expense in the accompanying statements of operations. The following table presents the outstanding balance, total amount of letters of credit outstanding, and available borrowing capacity under the Credit Agreement as of July 26, 2017 , June 30, 2017 , and December 31, 2016 : As of July 26, 2017 As of June 30, 2017 As of December 31, 2016 (in thousands) Credit facility balance (1) $ — $ — $ — Letters of credit (2) 200 200 200 Available borrowing capacity 924,800 924,800 1,164,800 Total aggregate lender commitment amount $ 925,000 $ 925,000 $ 1,165,000 ____________________________________________ (1) Unamortized deferred financing costs attributable to the credit facility are presented as a component of other noncurrent assets on the accompanying balance sheets and totaled $3.9 million and $5.9 million as of June 30, 2017 , and December 31, 2016 , respectively. (2) Letters of credit outstanding reduce the amount available under the credit facility on a dollar-for-dollar basis. Senior Notes The Company’s Senior Notes consist of 6.50% Senior Notes due 2021, 6.125% Senior Notes due 2022, 6.50% Senior Notes due 2023, 5.0% Senior Notes due 2024, 5.625% Senior Notes due 2025, and 6.75% Senior Notes due 2026 (collectively referred to as “Senior Notes”). The Senior Notes, net of unamortized deferred financing costs line on the accompanying balance sheets as of June 30, 2017 , and December 31, 2016 , consisted of the following: As of June 30, 2017 As of December 31, 2016 Principal Amount Unamortized Deferred Financing Costs Senior Notes, Net of Unamortized Deferred Financing Costs Principal Amount Unamortized Deferred Financing Costs Senior Notes, Net of Unamortized Deferred Financing Costs (in thousands) 6.50% Senior Notes due 2021 (1) (2) $ 344,611 $ 3,003 $ 341,608 $ 346,955 $ 3,372 $ 343,583 6.125% Senior Notes due 2022 (2) 561,796 6,390 555,406 561,796 6,979 554,817 6.50% Senior Notes due 2023 (2) 394,985 4,071 390,914 394,985 4,436 390,549 5.0% Senior Notes due 2024 500,000 6,072 493,928 500,000 6,533 493,467 5.625% Senior Notes due 2025 500,000 7,166 492,834 500,000 7,619 492,381 6.75% Senior Notes due 2026 500,000 7,660 492,340 500,000 8,078 491,922 Total $ 2,801,392 $ 34,362 $ 2,767,030 $ 2,803,736 $ 37,017 $ 2,766,719 ____________________________________________ (1) During the first quarter of 2017, the Company repurchased a total of $2.3 million in aggregate principal amount of 6.50% Senior Notes due 2021 in open market transactions at a slight premium. The Company canceled all of these repurchased Senior Notes upon cash settlement. (2) During the first quarter of 2016, the Company repurchased a total of $46.3 million in aggregate principal amount of certain of its Senior Notes in open market transactions for a settlement amount of $29.9 million , excluding interest. The Company recorded a net gain on extinguishment of debt of approximately $15.7 million for the six months ended June 30, 2016. This amount includes a gain of approximately $16.4 million associated with the discount realized upon repurchase, which was partially offset by approximately $0.7 million related to the acceleration of unamortized deferred financing costs. The Company canceled all of these repurchased Senior Notes upon cash settlement. 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 indentures governing the Senior Notes and was in compliance with all covenants as of June 30, 2017 , and through the filing of this report. The Company may redeem some or all of its Senior Notes prior to their maturity at redemption prices based on a premium, plus accrued and unpaid interest as described in the indentures governing the Senior Notes. Senior Convertible Notes On August 12, 2016 , the Company issued $172.5 million in aggregate principal amount of 1.50% Senior Convertible Notes due July 1, 2021 (the “Senior Convertible Notes”). The Senior Convertible 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. The Senior Convertible Notes mature on July 1, 2021 , unless earlier converted. Holders may convert their Senior Convertible Notes at their option at any time prior to January 1, 2021, only under certain circumstances as outlined in the indenture governing the Senior Convertible Notes and in Note 5 – Long-Term Debt to the Company’s consolidated financial statements in its 2016 Form 10-K. On or after January 1, 2021, until the maturity date, holders may convert their Senior Convertible Notes at any time. The Company may not redeem the Senior Convertible Notes prior to the maturity date. Upon conversion, the Senior Convertible Notes may be settled, at the Company’s election, in shares of the Company’s common stock, cash, or a combination of cash and common stock. Holders may convert their notes based on a conversion rate of 24.6914 shares of the Company’s common stock per $1,000 principal amount of the Senior Convertible Notes, which is equal to an initial conversion price of approximately $40.50 per share, subject to adjustment. The Company has initially elected a net-settlement method to satisfy its conversion obligation, which would result in the Company settling the principal amount in cash with any excess value in shares of the Company’s common stock. The Senior Convertible Notes were not convertible at the option of holders as of June 30, 2017 , or through the filing of this report. Notwithstanding the inability to convert, the if-converted value of the Senior Convertible Notes as of June 30, 2017 , did not exceed the principal amount. Upon the issuance of the Senior Convertible Notes, the Company recorded $132.3 million as the initial carrying amount of the debt component, which approximated its fair value at issuance, and was estimated by using an interest rate for nonconvertible debt with terms similar to the Senior Convertible Notes. The effective interest rate used was 7.25 percent . The $40.2 million excess of the principal amount of the Senior Convertible Notes over the fair value of the debt component was recorded as a debt discount and a corresponding increase in additional paid-in capital. The debt discount and debt-related issuance costs are amortized to the principal value of the Senior Convertible Notes as interest expense through the maturity date of July 1, 2021. Interest expense recognized on the Senior Convertible Notes related to the stated interest rate and amortization of the debt discount totaled $2.5 million and $4.9 million for the three and six months ended June 30, 2017 , respectively. The net carrying amount of the liability component of the Senior Convertible Notes, as reflected on the accompanying balance sheets as of June 30, 2017 , and December 31, 2016 , consisted of the following: As of June 30, 2017 As of December 31, 2016 (in thousands) Principal amount of Senior Convertible Notes $ 172,500 $ 172,500 Unamortized debt discount (33,913 ) (37,513 ) Unamortized deferred financing costs (3,669 ) (4,131 ) Net carrying amount $ 134,918 $ 130,856 The Company is subject to certain covenants under the indenture governing the Senior Convertible Notes and was in compliance with all covenants as of June 30, 2017 , and through the filing of this report. Capped Call Transactions In connection with the issuance of the Senior Convertible Notes, the Company entered into capped call transactions with affiliates of the underwriters of such issuance. The capped call transactions are generally expected to reduce the potential dilution upon conversion of the Senior Convertible Notes and/or partially offset any cash payments the Company is required to make in excess of the principal amount of converted Senior Convertible Notes in the event that the market price per share of the Company’s common stock is greater than the strike price of the capped call transactions, which initially corresponds to the approximate $40.50 per share conversion price of the Senior Convertible Notes. The cap price of the capped call transactions is initially $60.00 per share. If the market price per share exceeds the cap price of the capped call transactions, there could be dilution or there would not be an offset of such potential cash payments.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 6 - Commitments and Contingencies Commitments During the first quarter of 2017, the Company completed the divestiture of its outside-operated Eagle Ford shale assets. Upon closing of the sale, the Company is no longer subject to gathering, processing, and transportation throughput commitments totaling 514 Bcf of natural gas, 52 MMBbl of oil, and 13 MMBbl of NGLs, or $501.9 million of the potential undiscounted deficiency payments as of December 31, 2016. As of June 30, 2017 , the Company had total gathering, processing, transportation throughput, and purchase commitments with various third parties that require delivery of a minimum quantity of 883 Bcf of natural gas, 16 MMBbl of crude oil, and 25 MMBbl of water through 2028 and a minimum purchase quantity of 16 MMBbl of water by 2022. If the Company fails to deliver or purchase any product, as applicable, the aggregate undiscounted deficiency payments totaled approximately $456.4 million as of June 30, 2017. As of the filing of this report, the Company does not expect to incur any material shortfalls with regard to these commitments. Additionally, the Company entered into new and amended drilling rig contracts during the first half of 2017 and subsequent to June 30, 2017. As of July 26, 2017 , the Company’s total drilling rig commitment was $23.7 million ; however, if the Company terminated these rig contracts immediately, it would incur penalties of $15.1 million . There were no other material changes in commitments during the first half of 2017 . Please refer to Note 6 - Commitments and Contingencies to the Company’s consolidated financial statements in its 2016 Form 10-K for additional discussion of the Company’s commitments. 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 any pending litigation and claims are not expected to have a material effect on the results of operations, the financial position, or the cash flows of the Company.

Compensation Plans

Compensation Plans	6 Months Ended
	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation Plans	Note 7 - Compensation Plans Performance Share Units Under the Equity Incentive Compensation Plan The Company grants performance share units (“PSUs”) to eligible employees as part of its long-term equity compensation program. The number of shares of the Company’s common stock issued to settle PSUs ranges from 0% to 200% of the number of PSUs awarded and is determined based on certain performance criteria over a three -year measurement period. The performance criteria for 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. Compensation expense for PSUs is recognized within general and administrative and exploration expense over the vesting periods of the respective awards. Total compensation expense recorded for PSUs for the three months ended June 30, 2017 , and 2016 , was $1.7 million and $3.0 million , respectively, and $4.2 million and $5.9 million for the six months ended June 30, 2017 , and 2016 , respectively. As of June 30, 2017 , there was $10.6 million of total unrecognized compensation expense related to non-vested PSU awards, which is being amortized through 2019. There were no material changes to the outstanding and non-vested PSUs during the six months ended June 30, 2017 . Subsequent to June 30, 2017 , the Company granted 977,731 PSUs with a fair value of $15.5 million . These PSUs generally vest on the third anniversary of the date of the grant. Also, subsequent to June 30, 2017 , the Company settled PSUs that were granted in 2014 with no shares issued upon settlement as the grant settled at a zero multiplier. Restricted Stock Units Under the Equity Incentive Compensation Plan The Company grants restricted stock units (“RSUs”) as part of its long-term equity compensation program. Each RSU represents a right to receive one share of the Company’s common stock upon settlement of the award at the end of the specified vesting period. Compensation expense for RSUs is recognized within general and administrative expense and exploration expense over the vesting periods of the respective awards. Total compensation expense recorded for RSUs was $2.1 million and $3.3 million for the three months ended June 30, 2017 , and 2016 , respectively, and $4.6 million and $6.5 million for the six months ended June 30, 2017 , and 2016 , respectively. As of June 30, 2017 , there was $9.8 million of total unrecognized compensation expense related to non-vested RSU awards, which is being amortized through 2019. There were no material changes to the outstanding and non-vested RSUs during the six months ended June 30, 2017 . Subsequent to June 30, 2017 , the Company granted 1,010,298 RSUs with a fair value of $16.8 million . These RSUs generally vest one-third of the total grant on each of the next three anniversary dates of the grant. Also, subsequent to June 30, 2017 , the Company settled 243,951 RSUs that related to awards granted in previous years. The Company and the majority of grant participants mutually agreed to net share settle a portion of 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 169,891 net shares of common stock upon settlement of the awards. The remaining 74,060 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those RSUs. Director Shares During the second quarter of 2017 , the Company issued 71,573 shares of its common stock and 8,794 RSUs to its non-employee directors, under the Company’s Equity Incentive Compensation Plan, which fully vest on December 31, 2017. The Company issued 53,473 shares of its common stock to its non-employee directors during the second quarter of 2016. 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 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 either the first or last day of the purchase period. The ESPP is intended to qualify under Section 423 of the Internal Revenue Code (“IRC”). There were 123,678 and 140,853 shares issued under the ESPP during the second quarters of 2017 and 2016 , respectively. The fair value of ESPP grants is measured at the date of grant using the Black-Scholes option-pricing model.

Pension Benefits

Pension Benefits	6 Months Ended
	Jun. 30, 2017
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Pension Benefits	Note 8 - Pension Benefits Pension Plans The Company has a non-contributory defined benefit pension plan covering substantially all of its employees who joined the Company prior to January 1, 2015, and 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”). The Company froze the Pension Plans to new participants, effective as of December 31, 2015. Employees participating in the Pension Plans as of December 31, 2015, continue to earn benefits. Components of Net Periodic Benefit Cost for the Pension Plans The following table presents the components of the net periodic benefit cost for the Pension Plans: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Service cost $ 1,269 $ 2,113 $ 3,319 $ 4,100 Interest cost 617 830 1,344 1,454 Expected return on plan assets that reduces periodic pension benefit cost (563 ) (573 ) (1,122 ) (1,118 ) Amortization of prior service cost 5 5 9 9 Amortization of net actuarial loss 253 419 649 791 Net periodic benefit cost $ 1,581 $ 2,794 $ 4,199 $ 5,236 Prior service costs are amortized on a straight-line basis over the average remaining service period of active participants. Gains and losses in excess of 10 percent of the greater of the benefit obligation or the market-related value of assets are amortized over the average remaining service period of active participants. Contributions The Company contributed $7.0 million to the Qualified Pension Plan during the six months ended June 30, 2017 .

Earnings per Share

Earnings per Share	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Earnings per Share	Note 9 - Earnings Per Share Basic net income or loss per common share is calculated by dividing net income or loss available to common stockholders by the basic weighted-average number of common shares outstanding for the respective period. Diluted net income or loss per common share is calculated by dividing adjusted net income or loss by the diluted weighted-average number of common shares outstanding, which includes the effect of potentially dilutive securities. Potentially dilutive securities for this calculation consist of non-vested RSUs, contingent PSUs, and shares into which the Senior Convertible Notes are convertible, which are measured using the treasury stock method. 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, that would be issuable at the end of the respective reporting period, assuming that date was the end of the contingency period applicable to such PSUs. Please refer to Note 7 - Compensation Plans for additional discussion of the RSUs and PSUs granted and the net RSUs and PSUs settled subsequent to June 30, 2017. On August 12, 2016 , the Company issued $172.5 million in aggregate principal amount of Senior Convertible Notes due 2021 . Upon conversion, the Senior Convertible Notes may be settled, at the Company’s election, in shares of the Company’s common stock, cash, or a combination of cash and common stock. The Company has initially elected a net-settlement method to satisfy its conversion obligation, which would result in the Company settling the principal amount of the Senior Convertible Notes in cash and the excess conversion value in shares. However, the Company has not made this a formal legal irrevocable election and thereby reserves the right to settle the Senior Convertible Notes in any manner allowed under the indenture as business conditions warrant. Shares of the Company’s common stock traded at an average closing price below the $40.50 conversion price for the three and six months ended June 30, 2017 , and therefore, the Senior Convertible Notes had no dilutive impact. In connection with the offering of the Senior Convertible Notes, the Company entered into capped call transactions with affiliates of the underwriters that would effectively prevent dilution upon settlement up to the $60.00 cap price. The capped call transactions are not reflected in diluted net income (loss) per share, nor will they ever be, as they are anti-dilutive. Please refer to Note 5 - Long-Term Debt for additional discussion. When the Company recognizes a loss from continuing operations, as was the case for all periods presented, all potentially dilutive shares are anti-dilutive and are consequently excluded from the calculation of diluted net loss per common share. The following table details the weighted-average anti-dilutive securities for the periods presented: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Anti-dilutive 44 155 59 70 The following table sets forth the calculations of basic and diluted net loss per common share: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands, except per share amounts) Net loss $ (119,907 ) $ (168,681 ) $ (45,473 ) $ (515,891 ) Basic weighted-average common shares outstanding 111,277 68,102 111,274 68,090 Add: dilutive effect of non-vested RSUs and contingent PSUs — — — — Add: dilutive effect of Senior Convertible Notes — — — — Diluted weighted-average common shares outstanding 111,277 68,102 111,274 68,090 Basic net loss per common share $ (1.08 ) $ (2.48 ) $ (0.41 ) $ (7.58 ) Diluted net loss per common share $ (1.08 ) $ (2.48 ) $ (0.41 ) $ (7.58 )

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
	Jun. 30, 2017
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Derivative Financial Instruments	Note 10 - Derivative Financial Instruments Summary of Oil, Gas, and NGL Derivative Contracts in Place The Company has entered into various commodity derivative contracts to mitigate a portion of its exposure to potentially adverse market changes in commodity prices and the associated impact on cash flows. As of June 30, 2017 , all derivative counterparties were members of the Company’s credit facility lender group and all contracts were entered into for other-than-trading purposes. The Company’s commodity derivative contracts consist of swap and collar arrangements. In a typical commodity swap agreement, if the agreed upon published third-party index price (“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 arrangements, 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. As of June 30, 2017 , the Company had commodity derivative contracts outstanding as summarized in the tables below: Oil Swaps Contract Period NYMEX WTI Volumes Weighted-Average Contract Price (MBbls) (per Bbl) Third quarter 2017 1,340 $ 46.66 Fourth quarter 2017 1,254 $ 46.35 2018 1,493 $ 46.82 Total 4,087 Subsequent to June 30, 2017, the Company entered into derivative fixed price swap contracts for 2018 for a total of 2.0 million Bbls of oil production at a weighted-average contract price of $50.37 per Bbl. Oil Collars Contract Period NYMEX WTI Volumes Weighted- Average Floor Price Weighted- Average Ceiling Price (MBbls) (per Bbl) (per Bbl) Third quarter 2017 583 $ 45.00 $ 54.05 Fourth quarter 2017 1,086 $ 47.51 $ 56.05 2018 5,030 $ 50.00 $ 58.07 2019 3,128 $ 50.00 $ 58.84 Total 9,827 Oil Basis Swaps Contract Period Midland-Cushing Volumes Weighted-Average Contract Price (1) (MBbls) (per Bbl) Third quarter 2017 566 $ (1.62 ) Fourth quarter 2017 1,798 $ (1.52 ) 2018 6,868 $ (1.39 ) 2019 3,963 $ (1.45 ) Total 13,195 ____________________________________________ (1) Represents the price differential between WTI prices at Midland, Texas and WTI prices at Cushing, Oklahoma. Natural Gas Swaps Contract Period Sold Volumes Weighted-Average Contract Price Purchased Volumes (1) Weighted- Average Contract Price Net Volumes (BBtu) (per MMBtu) (BBtu) (per MMBtu) (BBtu) Third quarter 2017 23,657 $ 4.01 — $ — 23,657 Fourth quarter 2017 22,001 $ 3.98 — $ — 22,001 2018 93,014 $ 3.41 (30,606 ) $ 4.27 62,408 2019 41,394 $ 3.76 (24,415 ) $ 4.34 16,979 Total (2) 180,066 (55,021 ) 125,045 ____________________________________________ (1) During 2016, the Company restructured certain of its natural gas derivative contracts by buying fixed price volumes to offset existing 2018 and 2019 fixed price swap contracts totaling 55.0 million MMBtu. The Company then entered into new 2017 fixed price swap contracts totaling 38.6 million MMBtu with a contract price of $4.43 per MMBtu. No other cash or other consideration was included as part of the restructuring. (2) Total net volumes of natural gas swaps are comprised of IF El Paso Permian ( 1% ), IF HSC ( 97% ), and IF NNG Ventura ( 2% ). NGL Swaps OPIS Purity Ethane Mont Belvieu OPIS Propane Mont Belvieu Non-TET OPIS Normal Butane Mont Belvieu Non-TET OPIS Isobutane Mont Belvieu Non-TET OPIS Natural Gasoline Mont Belvieu Non-TET Contract Period Volumes Weighted-Average Contract Price Volumes Weighted-Average Volumes Weighted-Average Volumes Weighted-Average Volumes Weighted-Average (MBbls) (per Bbl) (MBbls) (per Bbl) (MBbls) (per Bbl) (MBbls) (per Bbl) (MBbls) (per Bbl) Third quarter 2017 906 $ 9.48 588 $ 21.91 163 $ 32.42 140 $ 33.28 222 $ 48.43 Fourth quarter 2017 966 $ 9.65 550 $ 21.91 149 $ 32.34 128 $ 33.23 203 $ 48.41 2018 4,017 $ 11.00 2,021 $ 23.38 225 $ 33.99 188 $ 33.56 305 $ 48.62 2019 3,112 $ 12.27 214 $ 22.66 — $ — — $ — — $ — 2020 539 $ 11.13 — $ — — $ — — $ — — $ — Total 9,540 3,373 537 456 730 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 $61.9 million as of June 30, 2017 , and a net liability of $91.7 million as of December 31, 2016 . The following tables detail the fair value of derivatives recorded in the accompanying balance sheets, by category: As of June 30, 2017 Derivative Assets Derivative Liabilities Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value (in thousands) Commodity contracts Current assets $ 85,962 Current liabilities $ 36,296 Commodity contracts Noncurrent assets 82,194 Noncurrent liabilities 69,915 Derivatives not designated as hedging instruments $ 168,156 $ 106,211 As of December 31, 2016 Derivative Assets Derivative Liabilities Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value (in thousands) Commodity contracts Current assets $ 54,521 Current liabilities $ 115,464 Commodity contracts Noncurrent assets 67,575 Noncurrent liabilities 98,340 Derivatives not designated as hedging instruments $ 122,096 $ 213,804 Offsetting of Derivative Assets and Liabilities As of June 30, 2017 , and December 31, 2016 , all derivative instruments held by the Company were subject to master netting arrangements with 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 settle on the same date and in the same currency. The Company’s agreements also provide that in the event of an early termination, the counterparties have the right to offset amounts owed or owing under that and any other agreement with the same counterparty. The Company’s accounting policy is to not offset these positions in its accompanying balance sheets. The following table provides a reconciliation between the gross assets and liabilities reflected on the accompanying balance sheets and the potential effects of master netting arrangements on the fair value of the Company’s derivative contracts: Derivative Assets Derivative Liabilities As of As of Offsetting of Derivative Assets and Liabilities June 30, December 31, 2016 June 30, December 31, 2016 (in thousands) Gross amounts presented in the accompanying balance sheets $ 168,156 $ 122,096 $ (106,211 ) $ (213,804 ) Amounts not offset in the accompanying balance sheets (64,628 ) (118,080 ) 64,628 118,080 Net amounts $ 103,528 $ 4,016 $ (41,583 ) $ (95,724 ) The following table summarizes the components of the net derivative (gain) loss presented in the accompanying statements of operations: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Derivative settlement (gain) loss: Oil contracts $ 2,754 $ (72,164 ) $ 11,838 $ (172,156 ) Gas contracts (21,751 ) (31,439 ) (39,257 ) (72,492 ) NGL contracts 2,694 1,893 11,109 (4,090 ) Total derivative settlement gain $ (16,303 ) $ (101,710 ) $ (16,310 ) $ (248,738 ) Total net derivative (gain) loss: Oil contracts $ (38,194 ) $ 60,773 $ (87,784 ) $ 50,341 Gas contracts (6,038 ) 62,489 (50,506 ) 38,466 NGL contracts (10,957 ) 40,089 (31,673 ) 60,316 Total net derivative (gain) loss $ (55,189 ) $ 163,351 $ (169,963 ) $ 149,123 Credit Related Contingent Features As of June 30, 2017 , and through the filing of this report, all of the Company’s derivative counterparties were members of the Company’s credit facility lender group. Under the Credit Agreement and derivative contracts, the Company is required to secure mortgages on assets having a value equal to at least 90 percent of the total PV-9 of the Company’s proved oil and gas properties evaluated in the most recent reserve report.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Text Block]	Note 11 - Fair Value Measurements The Company follows fair value measurement accounting guidance for all assets and liabilities measured at fair value. This 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 summarizes the Company’s assets and liabilities that are measured at fair value in the accompanying balance sheets and where they are classified within the fair value hierarchy as of June 30, 2017 : Level 1 Level 2 Level 3 (in thousands) Assets: Derivatives (1) $ — $ 168,156 $ — Liabilities: Derivatives (1) $ — $ 106,211 $ — ____________________________________________ (1) This represents a financial asset or liability that is measured at fair value on a recurring basis. The following table summarizes the Company’s assets and liabilities that are measured at fair value in the accompanying balance sheets and where they were classified within the fair value hierarchy as of December 31, 2016 : Level 1 Level 2 Level 3 (in thousands) Assets: Derivatives (1) $ — $ 122,096 $ — Total property and equipment, net (2) $ — $ — $ 88,205 Liabilities: Derivatives (1) $ — $ 213,804 $ — ____________________________________________ (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. All of the Company’s derivative counterparties are members of the Company’s credit facility lender group. 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, taking into account the Company’s credit rating, current credit facility margins, and any change in such margins since the last measurement date. The methods described above may result in a fair value estimate that may not be indicative of net realizable value or may not be reflective of future fair values and cash flows. While the Company believes that the valuation methods utilized are appropriate and consistent with authoritative accounting guidance and with other marketplace participants, the Company recognizes that third parties may use different methodologies or assumptions to determine the fair value of certain financial instruments that could result in a different estimate of fair value at the reporting date. Refer to Note 10 - Derivative Financial Instruments for more information regarding the Company’s derivative instruments. Proved and Unproved Oil and Gas Properties and Other Property and Equipment The Company did not have property and equipment measured at fair value within the accompanying balance sheets as of June 30, 2017 . Property and equipment, net measured at fair value totaled $88.2 million as of December 31, 2016 , and primarily consisted of the Company’s Powder River Basin assets, which were impaired at year-end as a result of downward performance reserve revisions. Proved oil and gas properties. Proved oil and gas property costs are evaluated for impairment and reduced to fair value when there is an indication 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 representative of the current operating environment, as selected by the Company’s management. The calculation of the discount rates are based on the best information available and the rates used ranged from 10 percent to 15 percent based on the reservoir specific weightings of future estimated proved and unproved cash flows as of June 30, 2017 , and December 31, 2016 . The Company believes the discount rates are representative of current market conditions and consider estimates of future cash payments, reserve categories, 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 forecast 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 forecast using OPIS Mont Belvieu pricing, for as long as the market is actively trading, after which a flat terminal price is used. Future operating costs are also adjusted as deemed appropriate for these estimates. The Company did not recognize any material impairment of proved properties expenses for the three or six months ended June 30, 2017 , or for the three months ended June 30, 2016 . The Company recorded impairment of proved properties expense of $269.8 million for the six months ended June 30, 2016, primarily related to the Company’s outside-operated Eagle Ford shale assets and the decline in expected cash flows driven by commodity price declines during the first quarter of 2016. Unproved oil and gas properties. 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: remaining lease terms, future development plans, risk weighted potential resource recovery, estimated reserve values, and estimated acreage value based on price(s) received for similar, recent acreage transactions by the Company or other market participants. There were no material abandonments or impairments of unproved properties expenses for the three or six months ended June 30, 2017 , or 2016 . Oil and gas properties held for sale. Proved and unproved properties and other property and equipment classified as held for sale, including the corresponding asset retirement obligation liability, are valued using a market approach based on an estimated net selling price, as evidenced by the most current bid prices received from third parties, if available, or by recent, comparable market transactions. If an estimated selling price is not available, the Company utilizes the various income valuation techniques discussed above. When assets no longer meet the criteria of assets held for sale, they are measured at the lower of the carrying value of the assets before being classified as held for sale, adjusted for any depletion, depreciation, and amortization expense that would have been recognized, or the fair value at the date they are reclassified to assets held for use. There were no assets held for sale that were recorded at fair value as of June 30, 2017 . However, for the six months ended June 30, 2017 , the Company recorded a $526.5 million write-down on its Divide County assets previously held for sale, of which $359.6 million was recorded in the first quarter of 2017 based on an estimated fair value less selling costs and $166.9 million was recorded in the second quarter of 2017 based on market conditions that existed on the date the Company decided to retain the assets. Certain assets held for sale as of June 30, 2016 , were written down by $68.3 million during the first quarter of 2016 and subsequently written up by $49.5 million in the second quarter of 2016 due to an increase in estimated selling prices, as evidenced by bid prices received from third parties. Certain of these assets were subsequently sold in the third quarter of 2016 for a small net gain due to successful marketing efforts. Please refer to Note 3 - Divestitures, Assets Held for Sale, and Acquisitions for additional discussion . Long-Term Debt The following table reflects the fair value of the Senior Notes and Senior Convertible Notes measured using Level 1 inputs based on quoted secondary market trading prices. These notes were not presented at fair value on the accompanying balance sheets as of June 30, 2017 , or December 31, 2016 , as they were recorded at carrying value, net of any unamortized discounts and deferred financing costs. Please refer to Note 5 - Long-Term Debt for additional discussion. As of June 30, 2017 As of December 31, 2016 Principal Amount Fair Value Principal Amount Fair Value (in thousands) 6.50% Senior Notes due 2021 $ 344,611 $ 338,794 $ 346,955 $ 354,546 6.125% Senior Notes due 2022 $ 561,796 $ 536,347 $ 561,796 $ 570,925 6.50% Senior Notes due 2023 $ 394,985 $ 377,211 $ 394,985 $ 403,134 5.0% Senior Notes due 2024 $ 500,000 $ 445,465 $ 500,000 $ 475,975 5.625% Senior Notes due 2025 $ 500,000 $ 449,335 $ 500,000 $ 485,000 6.75% Senior Notes due 2026 $ 500,000 $ 479,840 $ 500,000 $ 516,565 1.50% Senior Convertible Notes due 2021 $ 172,500 $ 154,612 $ 172,500 $ 202,189

Basis of Presentation, Signif19

Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards (Policies)	6 Months Ended
	Jun. 30, 2017
Basis of Presentation and Significant Accounting Policies [Abstract]
Consolidation, Policy [Policy Text Block]	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of SM Energy and its wholly-owned subsidiaries and have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and the instructions to Quarterly Report on Form 10-Q and Regulation S-X. These financial statements do not include all information and notes required by GAAP for annual financial statements. However, except as disclosed herein, there has been no material change in the information disclosed in the notes to consolidated financial statements included in SM Energy’s Annual Report on Form 10-K for the year ended December 31, 2016 (the “ 2016 Form 10-K”). In the opinion of management, all adjustments, consisting of normal recurring adjustments considered necessary for a fair presentation of interim financial information, have been included. Operating results for the periods presented are not necessarily indicative of expected results for the full year. In connection with the preparation of the Company’s unaudited condensed consolidated financial statements, the Company evaluated events subsequent to the balance sheet date of June 30, 2017 , and through the filing of this report. Certain prior period amounts have been reclassified to conform to the current presentation on the accompanying condensed consolidated financial statements.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Issued Accounting Standards Effective January 1, 2017, the Company adopted, using various transition methods, Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 is meant to simplify certain aspects of accounting for share-based arrangements, including income tax effects, accounting for forfeitures, and net share settlements. The Company adopted the various applicable amendments as summarized below: • On January 1, 2017, a $44.3 million cumulative-effect adjustment was made to retained earnings and a corresponding deferred tax asset was recorded for previously unrecognized excess tax benefits using a modified retrospective transition method. Additionally, going forward excess tax benefits will be presented in operating activities on the statement of cash flows. • Also on January 1, 2017, the Company elected to change its policy to account for forfeitures of share-based payment awards as they occur, rather than applying an estimated forfeiture rate. This change was made using a modified retrospective transition method and resulted in a net $0.7 million cumulative effect adjustment to retained earnings with a corresponding increase in additional paid-in capital and decrease in deferred tax assets. • As a result of adoption, excess tax benefits and deficiencies from share-based payments are expected to impact the Company’s effective tax rate between periods. Please refer to Note 4 - Income Taxes for additional discussion . In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”) . Under the new standard, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The FASB issued several amendments to the standard which provided additional implementation guidance and deferred the effective date of ASU 2014-09. While the Company does not expect net income (loss) or cash flows to be materially impacted, the Company is currently analyzing whether changes to total revenues and total expenses will be necessary to properly reflect revenue for certain pipeline gathering, transportation and gas processing agreements. The Company continues to evaluate the expected disclosure requirements, changes to relevant business practices, accounting policies, and control activities that will occur as a result of the adoption of this ASU, and has not yet developed estimates of the quantitative impact to its consolidated statements of financial position and operations. The Company plans to adopt the guidance using the modified retrospective method on the effective date of January 1, 2018. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) which requires lessees to recognize a right-of-use asset and a lease liability for virtually all leases currently classified as operating leases. The Company is currently analyzing the impact this standard has on the Company’s contract portfolio, including non-cancelable leases, drilling rig contracts, pipeline gathering, transportation and gas processing agreements, as well as other existing arrangements and is evaluating current accounting policies that will change as a result of this ASU. Appropriate systems, controls, and processes to support the recognition and disclosure of the new standard are also being evaluated. Based upon an initial assessment, adoption of this ASU is expected to result in: (i) an increase in assets and liabilities recorded, (ii) an increase in depreciation, depletion and amortization expense recorded, and (iii) an increase in interest expense recorded. The Company plans to adopt the guidance on the effective date of January 1, 2019. In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017-07”). This ASU requires presentation of service cost in the same line item(s) as other compensation costs arising from services rendered by employees during the period and presentation of the remaining components of net benefit cost in a separate line item, outside operating items. In addition, only the service cost component of net benefit cost is eligible for capitalization. The Company plans to adopt ASU 2017-07 on January 1, 2018, with retrospective application of the service cost component and the other components of net benefit cost in the consolidated statements of operations and prospective application for the capitalization of the service cost component of net benefit costs in assets. The Company is evaluating the impact of this ASU on its consolidated financial statements. Other than as disclosed above or in the 2016 Form 10-K, there are no other ASUs applicable to the Company that would have a material effect on the Company’s financial statements and related disclosures that have been issued but not yet adopted by the Company as of June 30, 2017 , and through the filing of this report.
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. 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. All of the Company’s derivative counterparties are members of the Company’s credit facility lender group. 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, taking into account the Company’s credit rating, current credit facility margins, and any change in such margins since the last measurement date. The methods described above may result in a fair value estimate that may not be indicative of net realizable value or may not be reflective of future fair values and cash flows. While the Company believes that the valuation methods utilized are appropriate and consistent with authoritative accounting guidance and with other marketplace participants, the Company recognizes that third parties may use different methodologies or assumptions to determine the fair value of certain financial instruments that could result in a different estimate of fair value at the reporting date. Refer to Note 10 - Derivative Financial Instruments for more information regarding the Company’s derivative instruments.
Property, Plant and Equipment, Impairment [Policy Text Block]	Proved and Unproved Oil and Gas Properties and Other Property and Equipment The Company did not have property and equipment measured at fair value within the accompanying balance sheets as of June 30, 2017 . Property and equipment, net measured at fair value totaled $88.2 million as of December 31, 2016 , and primarily consisted of the Company’s Powder River Basin assets, which were impaired at year-end as a result of downward performance reserve revisions. Proved oil and gas properties. Proved oil and gas property costs are evaluated for impairment and reduced to fair value when there is an indication 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 representative of the current operating environment, as selected by the Company’s management. The calculation of the discount rates are based on the best information available and the rates used ranged from 10 percent to 15 percent based on the reservoir specific weightings of future estimated proved and unproved cash flows as of June 30, 2017 , and December 31, 2016 . The Company believes the discount rates are representative of current market conditions and consider estimates of future cash payments, reserve categories, 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 forecast 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 forecast using OPIS Mont Belvieu pricing, for as long as the market is actively trading, after which a flat terminal price is used. Future operating costs are also adjusted as deemed appropriate for these estimates. The Company did not recognize any material impairment of proved properties expenses for the three or six months ended June 30, 2017 , or for the three months ended June 30, 2016 . The Company recorded impairment of proved properties expense of $269.8 million for the six months ended June 30, 2016, primarily related to the Company’s outside-operated Eagle Ford shale assets and the decline in expected cash flows driven by commodity price declines during the first quarter of 2016. Unproved oil and gas properties. 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: remaining lease terms, future development plans, risk weighted potential resource recovery, estimated reserve values, and estimated acreage value based on price(s) received for similar, recent acreage transactions by the Company or other market participants. There were no material abandonments or impairments of unproved properties expenses for the three or six months ended June 30, 2017 , or 2016 . Oil and gas properties held for sale. Proved and unproved properties and other property and equipment classified as held for sale, including the corresponding asset retirement obligation liability, are valued using a market approach based on an estimated net selling price, as evidenced by the most current bid prices received from third parties, if available, or by recent, comparable market transactions. If an estimated selling price is not available, the Company utilizes the various income valuation techniques discussed above. When assets no longer meet the criteria of assets held for sale, they are measured at the lower of the carrying value of the assets before being classified as held for sale, adjusted for any depletion, depreciation, and amortization expense that would have been recognized, or the fair value at the date they are reclassified to assets held for use. There were no assets held for sale that were recorded at fair value as of June 30, 2017 . However, for the six months ended June 30, 2017 , the Company recorded a $526.5 million write-down on its Divide County assets previously held for sale, of which $359.6 million was recorded in the first quarter of 2017 based on an estimated fair value less selling costs and $166.9 million was recorded in the second quarter of 2017 based on market conditions that existed on the date the Company decided to retain the assets. Certain assets held for sale as of June 30, 2016 , were written down by $68.3 million during the first quarter of 2016 and subsequently written up by $49.5 million in the second quarter of 2016 due to an increase in estimated selling prices, as evidenced by bid prices received from third parties. Certain of these assets were subsequently sold in the third quarter of 2016 for a small net gain due to successful marketing efforts. Please refer to Note 3 - Divestitures, Assets Held for Sale, and Acquisitions for additional discussion .

Divestitures, Assets Held for20

Divestitures, Assets Held for Sale, and Acquisitions (Tables)	6 Months Ended
	Jun. 30, 2017
Non-Operated Eagle Ford Divestiture 2017 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations [Table Text Block]	The following table presents income (loss) before income taxes from the outside-operated Eagle Ford shale assets sold for the three and six months ended June 30, 2017 , and 2016 . This divestiture is considered a disposal of a significant asset group. For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Income (loss) before income taxes (1) $ — $ 12,832 $ 24,324 $ (273,567 ) ____________________________________________ (1) Income (loss) before income taxes reflects oil, gas, and NGL production revenue, less oil, gas, and NGL production expense, and depletion, depreciation, amortization, and asset retirement obligation liability accretion. Additionally, income (loss) before income taxes included impairment of proved properties expense of approximately $269.6 million for the six months ended June 30, 2016 .

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Schedule of provision for income taxes	The provision for income taxes for the three and six months ended June 30, 2017 , and 2016 , consisted of the following: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Current portion of income tax benefit (expense): Federal $ 4,607 $ — $ (2,832 ) $ — State 2,439 (77 ) (1,403 ) (241 ) Deferred portion of income tax benefit 64,015 95,975 30,790 291,014 Income tax benefit $ 71,061 $ 95,898 $ 26,555 $ 290,773 Effective tax rate 37.2 % 36.2 % 36.9 % 36.0 %

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Schedule of Line of Credit Facilities [Table Text Block]	The following table presents the outstanding balance, total amount of letters of credit outstanding, and available borrowing capacity under the Credit Agreement as of July 26, 2017 , June 30, 2017 , and December 31, 2016 : As of July 26, 2017 As of June 30, 2017 As of December 31, 2016 (in thousands) Credit facility balance (1) $ — $ — $ — Letters of credit (2) 200 200 200 Available borrowing capacity 924,800 924,800 1,164,800 Total aggregate lender commitment amount $ 925,000 $ 925,000 $ 1,165,000 ____________________________________________ (1) Unamortized deferred financing costs attributable to the credit facility are presented as a component of other noncurrent assets on the accompanying balance sheets and totaled $3.9 million and $5.9 million as of June 30, 2017 , and December 31, 2016 , respectively. (2) Letters of credit outstanding reduce the amount available under the credit facility on a dollar-for-dollar basis.
Schedule of Long-term Debt Instruments [Table Text Block]	The Senior Notes, net of unamortized deferred financing costs line on the accompanying balance sheets as of June 30, 2017 , and December 31, 2016 , consisted of the following: As of June 30, 2017 As of December 31, 2016 Principal Amount Unamortized Deferred Financing Costs Senior Notes, Net of Unamortized Deferred Financing Costs Principal Amount Unamortized Deferred Financing Costs Senior Notes, Net of Unamortized Deferred Financing Costs (in thousands) 6.50% Senior Notes due 2021 (1) (2) $ 344,611 $ 3,003 $ 341,608 $ 346,955 $ 3,372 $ 343,583 6.125% Senior Notes due 2022 (2) 561,796 6,390 555,406 561,796 6,979 554,817 6.50% Senior Notes due 2023 (2) 394,985 4,071 390,914 394,985 4,436 390,549 5.0% Senior Notes due 2024 500,000 6,072 493,928 500,000 6,533 493,467 5.625% Senior Notes due 2025 500,000 7,166 492,834 500,000 7,619 492,381 6.75% Senior Notes due 2026 500,000 7,660 492,340 500,000 8,078 491,922 Total $ 2,801,392 $ 34,362 $ 2,767,030 $ 2,803,736 $ 37,017 $ 2,766,719 ____________________________________________ (1) During the first quarter of 2017, the Company repurchased a total of $2.3 million in aggregate principal amount of 6.50% Senior Notes due 2021 in open market transactions at a slight premium. The Company canceled all of these repurchased Senior Notes upon cash settlement. (2) During the first quarter of 2016, the Company repurchased a total of $46.3 million in aggregate principal amount of certain of its Senior Notes in open market transactions for a settlement amount of $29.9 million , excluding interest. The Company recorded a net gain on extinguishment of debt of approximately $15.7 million for the six months ended June 30, 2016. This amount includes a gain of approximately $16.4 million associated with the discount realized upon repurchase, which was partially offset by approximately $0.7 million related to the acceleration of unamortized deferred financing costs. The Company canceled all of these repurchased Senior Notes upon cash settlement.
Convertible Debt [Table Text Block]	The net carrying amount of the liability component of the Senior Convertible Notes, as reflected on the accompanying balance sheets as of June 30, 2017 , and December 31, 2016 , consisted of the following: As of June 30, 2017 As of December 31, 2016 (in thousands) Principal amount of Senior Convertible Notes $ 172,500 $ 172,500 Unamortized debt discount (33,913 ) (37,513 ) Unamortized deferred financing costs (3,669 ) (4,131 ) Net carrying amount $ 134,918 $ 130,856

Pension Benefits (Tables)

Pension Benefits (Tables)	6 Months Ended
	Jun. 30, 2017
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Components of the net periodic benefit cost for both the Qualified and the Nonqualified Pension Plan	The following table presents the components of the net periodic benefit cost for the Pension Plans: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Service cost $ 1,269 $ 2,113 $ 3,319 $ 4,100 Interest cost 617 830 1,344 1,454 Expected return on plan assets that reduces periodic pension benefit cost (563 ) (573 ) (1,122 ) (1,118 ) Amortization of prior service cost 5 5 9 9 Amortization of net actuarial loss 253 419 649 791 Net periodic benefit cost $ 1,581 $ 2,794 $ 4,199 $ 5,236

Earnings per Share (Tables)

Earnings per Share (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]	The following table details the weighted-average anti-dilutive securities for the periods presented: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Anti-dilutive 44 155 59 70
Schedule of calculation of basic and diluted earnings per share	The following table sets forth the calculations of basic and diluted net loss per common share: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands, except per share amounts) Net loss $ (119,907 ) $ (168,681 ) $ (45,473 ) $ (515,891 ) Basic weighted-average common shares outstanding 111,277 68,102 111,274 68,090 Add: dilutive effect of non-vested RSUs and contingent PSUs — — — — Add: dilutive effect of Senior Convertible Notes — — — — Diluted weighted-average common shares outstanding 111,277 68,102 111,274 68,090 Basic net loss per common share $ (1.08 ) $ (2.48 ) $ (0.41 ) $ (7.58 ) Diluted net loss per common share $ (1.08 ) $ (2.48 ) $ (0.41 ) $ (7.58 )

Derivative Financial Instrume25

Derivative Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2017
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]	As of June 30, 2017 , the Company had commodity derivative contracts outstanding as summarized in the tables below: Oil Swaps Contract Period NYMEX WTI Volumes Weighted-Average Contract Price (MBbls) (per Bbl) Third quarter 2017 1,340 $ 46.66 Fourth quarter 2017 1,254 $ 46.35 2018 1,493 $ 46.82 Total 4,087 Subsequent to June 30, 2017, the Company entered into derivative fixed price swap contracts for 2018 for a total of 2.0 million Bbls of oil production at a weighted-average contract price of $50.37 per Bbl. Oil Collars Contract Period NYMEX WTI Volumes Weighted- Average Floor Price Weighted- Average Ceiling Price (MBbls) (per Bbl) (per Bbl) Third quarter 2017 583 $ 45.00 $ 54.05 Fourth quarter 2017 1,086 $ 47.51 $ 56.05 2018 5,030 $ 50.00 $ 58.07 2019 3,128 $ 50.00 $ 58.84 Total 9,827 Oil Basis Swaps Contract Period Midland-Cushing Volumes Weighted-Average Contract Price (1) (MBbls) (per Bbl) Third quarter 2017 566 $ (1.62 ) Fourth quarter 2017 1,798 $ (1.52 ) 2018 6,868 $ (1.39 ) 2019 3,963 $ (1.45 ) Total 13,195 ____________________________________________ (1) Represents the price differential between WTI prices at Midland, Texas and WTI prices at Cushing, Oklahoma. Natural Gas Swaps Contract Period Sold Volumes Weighted-Average Contract Price Purchased Volumes (1) Weighted- Average Contract Price Net Volumes (BBtu) (per MMBtu) (BBtu) (per MMBtu) (BBtu) Third quarter 2017 23,657 $ 4.01 — $ — 23,657 Fourth quarter 2017 22,001 $ 3.98 — $ — 22,001 2018 93,014 $ 3.41 (30,606 ) $ 4.27 62,408 2019 41,394 $ 3.76 (24,415 ) $ 4.34 16,979 Total (2) 180,066 (55,021 ) 125,045 ____________________________________________ (1) During 2016, the Company restructured certain of its natural gas derivative contracts by buying fixed price volumes to offset existing 2018 and 2019 fixed price swap contracts totaling 55.0 million MMBtu. The Company then entered into new 2017 fixed price swap contracts totaling 38.6 million MMBtu with a contract price of $4.43 per MMBtu. No other cash or other consideration was included as part of the restructuring. (2) Total net volumes of natural gas swaps are comprised of IF El Paso Permian ( 1% ), IF HSC ( 97% ), and IF NNG Ventura ( 2% ). NGL Swaps OPIS Purity Ethane Mont Belvieu OPIS Propane Mont Belvieu Non-TET OPIS Normal Butane Mont Belvieu Non-TET OPIS Isobutane Mont Belvieu Non-TET OPIS Natural Gasoline Mont Belvieu Non-TET Contract Period Volumes Weighted-Average Contract Price Volumes Weighted-Average Volumes Weighted-Average Volumes Weighted-Average Volumes Weighted-Average (MBbls) (per Bbl) (MBbls) (per Bbl) (MBbls) (per Bbl) (MBbls) (per Bbl) (MBbls) (per Bbl) Third quarter 2017 906 $ 9.48 588 $ 21.91 163 $ 32.42 140 $ 33.28 222 $ 48.43 Fourth quarter 2017 966 $ 9.65 550 $ 21.91 149 $ 32.34 128 $ 33.23 203 $ 48.41 2018 4,017 $ 11.00 2,021 $ 23.38 225 $ 33.99 188 $ 33.56 305 $ 48.62 2019 3,112 $ 12.27 214 $ 22.66 — $ — — $ — — $ — 2020 539 $ 11.13 — $ — — $ — — $ — — $ — Total 9,540 3,373 537 456 730
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 June 30, 2017 Derivative Assets Derivative Liabilities Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value (in thousands) Commodity contracts Current assets $ 85,962 Current liabilities $ 36,296 Commodity contracts Noncurrent assets 82,194 Noncurrent liabilities 69,915 Derivatives not designated as hedging instruments $ 168,156 $ 106,211 As of December 31, 2016 Derivative Assets Derivative Liabilities Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value (in thousands) Commodity contracts Current assets $ 54,521 Current liabilities $ 115,464 Commodity contracts Noncurrent assets 67,575 Noncurrent liabilities 98,340 Derivatives not designated as hedging instruments $ 122,096 $ 213,804
Schedule of the potential effects of master netting arrangements [Table Text Block]	The following table provides a reconciliation between the gross assets and liabilities reflected on the accompanying balance sheets and the potential effects of master netting arrangements on the fair value of the Company’s derivative contracts: Derivative Assets Derivative Liabilities As of As of Offsetting of Derivative Assets and Liabilities June 30, December 31, 2016 June 30, December 31, 2016 (in thousands) Gross amounts presented in the accompanying balance sheets $ 168,156 $ 122,096 $ (106,211 ) $ (213,804 ) Amounts not offset in the accompanying balance sheets (64,628 ) (118,080 ) 64,628 118,080 Net amounts $ 103,528 $ 4,016 $ (41,583 ) $ (95,724 )
Schedule of derivative (gain) loss	The following table summarizes the components of the net derivative (gain) loss presented in the accompanying statements of operations: For the Three Months Ended For the Six Months Ended 2017 2016 2017 2016 (in thousands) Derivative settlement (gain) loss: Oil contracts $ 2,754 $ (72,164 ) $ 11,838 $ (172,156 ) Gas contracts (21,751 ) (31,439 ) (39,257 ) (72,492 ) NGL contracts 2,694 1,893 11,109 (4,090 ) Total derivative settlement gain $ (16,303 ) $ (101,710 ) $ (16,310 ) $ (248,738 ) Total net derivative (gain) loss: Oil contracts $ (38,194 ) $ 60,773 $ (87,784 ) $ 50,341 Gas contracts (6,038 ) 62,489 (50,506 ) 38,466 NGL contracts (10,957 ) 40,089 (31,673 ) 60,316 Total net derivative (gain) loss $ (55,189 ) $ 163,351 $ (169,963 ) $ 149,123

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]	The following table summarizes the Company’s assets and liabilities that are measured at fair value in the accompanying balance sheets and where they are classified within the fair value hierarchy as of June 30, 2017 : Level 1 Level 2 Level 3 (in thousands) Assets: Derivatives (1) $ — $ 168,156 $ — Liabilities: Derivatives (1) $ — $ 106,211 $ — ____________________________________________ (1) This represents a financial asset or liability that is measured at fair value on a recurring basis. The following table summarizes the Company’s assets and liabilities that are measured at fair value in the accompanying balance sheets and where they were classified within the fair value hierarchy as of December 31, 2016 : Level 1 Level 2 Level 3 (in thousands) Assets: Derivatives (1) $ — $ 122,096 $ — Total property and equipment, net (2) $ — $ — $ 88,205 Liabilities: Derivatives (1) $ — $ 213,804 $ — ____________________________________________ (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.
Long Term Debt Fair Value [Table Text Block]	The following table reflects the fair value of the Senior Notes and Senior Convertible Notes measured using Level 1 inputs based on quoted secondary market trading prices. These notes were not presented at fair value on the accompanying balance sheets as of June 30, 2017 , or December 31, 2016 , as they were recorded at carrying value, net of any unamortized discounts and deferred financing costs. Please refer to Note 5 - Long-Term Debt for additional discussion. As of June 30, 2017 As of December 31, 2016 Principal Amount Fair Value Principal Amount Fair Value (in thousands) 6.50% Senior Notes due 2021 $ 344,611 $ 338,794 $ 346,955 $ 354,546 6.125% Senior Notes due 2022 $ 561,796 $ 536,347 $ 561,796 $ 570,925 6.50% Senior Notes due 2023 $ 394,985 $ 377,211 $ 394,985 $ 403,134 5.0% Senior Notes due 2024 $ 500,000 $ 445,465 $ 500,000 $ 475,975 5.625% Senior Notes due 2025 $ 500,000 $ 449,335 $ 500,000 $ 485,000 6.75% Senior Notes due 2026 $ 500,000 $ 479,840 $ 500,000 $ 516,565 1.50% Senior Convertible Notes due 2021 $ 172,500 $ 154,612 $ 172,500 $ 202,189

Basis of Presentation, Signif27

Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards Recently Issued Accounting Standards (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Jan. 01, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 786,608		$ 794,020
ASU 2016-09 Cumulative Effect Adjustment for Timing of Recognition of Excess Tax Benefits [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		$ 44,300
ASU 2016-09 Cumulative Effect of Actual Forfeiture Rate [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		$ (700)

Divestitures, Assets Held for28

Divestitures, Assets Held for Sale, and Acquisitions Divestitures and Assets Held for Sale (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended		7 Months Ended
		Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from the sale of oil and gas properties						$ 766,247	$ 12,967
Net gain (loss) on divestiture activity		$ (167,133)		$ 50,046		(129,670)	(18,975)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		(190,968)		(264,579)		(72,028)	(806,664)
Impairment of Proved Oil and Gas Properties		3,806		0		3,806	269,785
Disposal Group, Including Discontinued Operation, Assets, Current		18,739				18,739		$ 18,739	$ 372,621
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down				(49,500)	$ 68,300
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from the sale of oil and gas properties						747,400
Net gain (loss) on divestiture activity						397,400
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	[1]	0		$ 12,832		24,324	(273,567)
Impairment of Proved Oil and Gas Properties							$ 269,600
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Divide County Divestiture 2017 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from the sale of oil and gas properties		24,600
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Raven/Bear Den Divestiture 2016 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain (loss) on divestiture activity								$ 29,100
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Divide County Disposal Group [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of Proved Oil and Gas Properties						$ 526,500
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down		$ 166,900	$ 359,600
[1]	Income (loss) before income taxes reflects oil, gas, and NGL production revenue, less oil, gas, and NGL production expense, and depletion, depreciation, amortization, and asset retirement obligation liability accretion. Additionally, income (loss) before income taxes included impairment of proved properties expense of approximately $269.6 million for the six months ended June 30, 2016.

Divestitures, Assets Held for29

Divestitures, Assets Held for Sale, and Acquisitions Acquisitions (Details) $ in Thousands	3 Months Ended	6 Months Ended			9 Months Ended
	Mar. 31, 2017USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2017USD ($)a	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)
Business Acquisition [Line Items]
Payments to Acquire Oil and Gas Property and Equipment			$ 88,140	$ 17,751
Other Howard and Martin Counties Trades [Member]
Business Acquisition [Line Items]
Non-monetary Trade, Acreage Acquired | a			6,550
Non-monetary Trade, Acreage Exchanged | a			5,700
Rock Oil Acquisition 2016 [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 7,400				$ 998,400
Other Midland Basin Acquisition 2017 [Member]
Business Acquisition [Line Items]
Net Acres Acquired | a			3,400
Payments to Acquire Oil and Gas Property and Equipment			$ 72,300
QStar Acquisition 2016 [Member]
Business Acquisition [Line Items]
Payments to Acquire Oil and Gas Property and Equipment			$ 7,100
Acquisition of Oil And Gas Property And Equipment, Consideration Transferred		$ 1,600,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Components of the provision for income taxes
Federal	$ 4,607	$ 0	$ (2,832)	$ 0
State	2,439	(77)	(1,403)	(241)
Deferred portion of income tax (expense) benefit	64,015	95,975	30,790	291,014
Income tax (expense) benefit	$ 71,061	$ 95,898	$ 26,555	$ 290,773
Effective tax rate	37.20%	36.20%	36.90%	36.00%

Long-Term Debt Revolving Credit

Long-Term Debt Revolving Credit Facility (Details) $ in Thousands		6 Months Ended
		Jun. 30, 2017USD ($)	Jul. 26, 2017USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Long-term Line of Credit, Noncurrent		$ 0		$ 0
Line of Credit [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		2,500,000
Line of Credit Facility, Current Borrowing Capacity		925,000		1,165,000
Accelerated Amortization of Debt Issuance Costs Related To Borrowing Base And Lender Commitment Revisions		1,100
Long-term Line of Credit, Noncurrent	[1]	0		0
Letters of Credit Outstanding, Amount	[2]	200		200
Line of Credit Facility, Remaining Borrowing Capacity		924,800		1,164,800
Unamortized Debt Issuance Expense		$ 3,900		$ 5,900
Maximum [Member] | Line of Credit [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Compliance, Senior Secured Debt To Adjusted EBITDAX Ratio		2.75
Minimum [Member] | Line of Credit [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Compliance, Adjusted Current Ratio		1
Debt Instrument, Covenant Compliance, Adjusted EBITDAX To Interest Expense		2
Subsequent Event [Member] | Line of Credit [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity			$ 925,000
Long-term Line of Credit, Noncurrent			0
Letters of Credit Outstanding, Amount	[2]		200
Line of Credit Facility, Remaining Borrowing Capacity			$ 924,800
[1]	Unamortized deferred financing costs attributable to the credit facility are presented as a component of other noncurrent assets on the accompanying balance sheets and totaled $3.9 million and $5.9 million as of June 30, 2017, and December 31, 2016, respectively.
[2]	Letters of credit outstanding reduce the amount available under the credit facility on a dollar-for-dollar basis.

Long-Term Debt Senior Notes (De

Long-Term Debt Senior Notes (Details)		Jun. 30, 2017USD ($)$ / shares		Jun. 30, 2017USD ($)$ / shares		Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)$ / shares		Jun. 30, 2016USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)		Aug. 12, 2016USD ($)	Mar. 31, 2016USD ($)
Debt Instrument [Line Items]
Senior Notes, Noncurrent		$ 2,767,030,000		$ 2,767,030,000			$ 2,767,030,000				$ 2,766,719,000
Gain (loss) on extinguishment of debt				0		$ 0	(35,000)		$ 15,722,000
Gains (losses) on extinguishment of debt, noncash portion							(22,000)		15,722,000
Convertible Debt, Noncurrent		$ 134,918,000		$ 134,918,000			$ 134,918,000				130,856,000
Capped Call, Cap Price | $ / shares		$ 60		$ 60			$ 60
6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[1]	$ 344,611,000		$ 344,611,000			$ 344,611,000
Unamortized Debt Issuance Expense		(3,003,000)	[1]	(3,003,000)	[1]		(3,003,000)	[1]			(3,372,000)	[2]
Senior Notes, Noncurrent		341,608,000	[1]	341,608,000	[1]		341,608,000	[1]			343,583,000	[2]
6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		561,796,000		561,796,000			561,796,000
Unamortized Debt Issuance Expense		(6,390,000)		(6,390,000)			(6,390,000)				(6,979,000)	[2]
Senior Notes, Noncurrent		555,406,000		555,406,000			555,406,000				554,817,000	[2]
6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		394,985,000		394,985,000			394,985,000
Unamortized Debt Issuance Expense		(4,071,000)		(4,071,000)			(4,071,000)				(4,436,000)	[2]
Senior Notes, Noncurrent		390,914,000		390,914,000			390,914,000				390,549,000	[2]
5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		500,000,000		500,000,000			500,000,000
Unamortized Debt Issuance Expense		(6,072,000)		(6,072,000)			(6,072,000)				(6,533,000)
Senior Notes, Noncurrent		493,928,000		493,928,000			493,928,000				493,467,000
5.625% Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		500,000,000		500,000,000			500,000,000
Unamortized Debt Issuance Expense		(7,166,000)		(7,166,000)			(7,166,000)				(7,619,000)
Senior Notes, Noncurrent		492,834,000		492,834,000			492,834,000				492,381,000
6.75% Senior Notes Due 2026 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		500,000,000		500,000,000			500,000,000
Unamortized Debt Issuance Expense		(7,660,000)		(7,660,000)			(7,660,000)				(8,078,000)
Senior Notes, Noncurrent		492,340,000		492,340,000			492,340,000				491,922,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		2,801,392,000		2,801,392,000			2,801,392,000				2,803,736,000
Unamortized Debt Issuance Expense		(34,362,000)		(34,362,000)			(34,362,000)				(37,017,000)
Senior Notes, Noncurrent		$ 2,767,030,000		$ 2,767,030,000			$ 2,767,030,000				2,766,719,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount														$ 46,300,000
Debt Instrument, Repurchased Settlement Amount									29,900,000
Gain (loss) on extinguishment of debt									15,700,000
Debt Instrument, Repurchase Discount									16,400,000
Gains (losses) on extinguishment of debt, noncash portion									$ (700,000)
Senior Notes [Member] | 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%		6.50%			6.50%
Debt Instrument, Face Amount		$ 344,611,000		$ 344,611,000			$ 344,611,000				346,955,000
Debt Instrument, Repurchased Face Amount										$ 2,300,000
Senior Notes [Member] | 6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.125%		6.125%			6.125%
Debt Instrument, Face Amount		$ 561,796,000		$ 561,796,000			$ 561,796,000				561,796,000
Senior Notes [Member] | 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%		6.50%			6.50%
Debt Instrument, Face Amount		$ 394,985,000		$ 394,985,000			$ 394,985,000				394,985,000
Senior Notes [Member] | 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.00%		5.00%			5.00%
Debt Instrument, Face Amount		$ 500,000,000		$ 500,000,000			$ 500,000,000				500,000,000
Senior Notes [Member] | 5.625% Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.625%		5.625%			5.625%
Debt Instrument, Face Amount		$ 500,000,000		$ 500,000,000			$ 500,000,000				500,000,000
Senior Notes [Member] | 6.75% Senior Notes Due 2026 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.75%		6.75%			6.75%
Debt Instrument, Face Amount		$ 500,000,000		$ 500,000,000			$ 500,000,000				500,000,000
Convertible Debt [Member] | 1.50% Senior Convertible Notes Due 2021 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.50%		1.50%			1.50%
Debt Instrument, Face Amount		$ 172,500,000		$ 172,500,000			$ 172,500,000				172,500,000
Unamortized Debt Issuance Expense		(3,669,000)		(3,669,000)			$ (3,669,000)				(4,131,000)
Debt Instrument, Convertible, Conversion Ratio							24.6914
Debt Instrument, Principal Amount of Note		$ 1,000		$ 1,000			$ 1,000
Debt Instrument, Convertible, Conversion Price | $ / shares		$ 40.50		$ 40.50			$ 40.50
Debt Instrument, Convertible, Initial Fair Value of Liability Component													$ 132,300,000
Debt Instrument, Convertible, Comparable Yield		7.25%
Debt Instrument, Convertible, Initial Value of Equity Component													$ 40,200,000
Interest Expense, Debt				$ 2,500,000			$ 4,900,000
Debt Instrument, Unamortized Discount		$ (33,913,000)		(33,913,000)			(33,913,000)				(37,513,000)
Convertible Debt, Noncurrent		$ 134,918,000		$ 134,918,000			$ 134,918,000				$ 130,856,000
[1]	During the first quarter of 2017, the Company repurchased a total of $2.3 million in aggregate principal amount of 6.50% Senior Notes due 2021 in open market transactions at a slight premium. The Company canceled all of these repurchased Senior Notes upon cash settlement.
[2]	During the first quarter of 2016, the Company repurchased a total of $46.3 million in aggregate principal amount of certain of its Senior Notes in open market transactions for a settlement amount of $29.9 million, excluding interest. The Company recorded a net gain on extinguishment of debt of approximately $15.7 million for the six months ended June 30, 2016. This amount includes a gain of approximately $16.4 million associated with the discount realized upon repurchase, which was partially offset by approximately $0.7 million related to the acceleration of unamortized deferred financing costs. The Company canceled all of these repurchased Senior Notes upon cash settlement.

Commitments and Contingencies (

Commitments and Contingencies (Details) MMcf in Thousands, $ in Millions	Jun. 30, 2017USD ($)MMcfMMBbls	Jun. 30, 2017USD ($)MMcfMMBbls	Jul. 26, 2017USD ($)	Dec. 31, 2016USD ($)MMcfMMBbls
Other Commitments [Line Items]
Document Fiscal Year Focus		2,017
Gas gathering and Oil and Gas Through-put Commitments [Member]
Other Commitments [Line Items]
Contractual Obligation | $	$ 456.4	$ 456.4
Water Pipeline Commitment [Member]
Other Commitments [Line Items]
Water Delivery Commitments and Contracts, Remaining Contractual Volume	25	25
Water Purchase Commitment [Member]
Other Commitments [Line Items]
Long-term Purchase Commitment, Minimum Volume Required	16
Natural Gas Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume | MMcf	883	883
Crude Oil Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume	16	16
Non-Operated Eagle Ford Divestiture 2017 [Member] | Gas gathering and Oil and Gas Through-put Commitments [Member]
Other Commitments [Line Items]
Contractual Obligation, Non-Operated Eagle Ford Assets | $				$ 501.9
Non-Operated Eagle Ford Divestiture 2017 [Member] | Natural Gas Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume on Non-Operated Eagle Ford Assets | MMcf				514
Non-Operated Eagle Ford Divestiture 2017 [Member] | Crude Oil Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume on Non-Operated Eagle Ford Assets				52
Non-Operated Eagle Ford Divestiture 2017 [Member] | Natural Gas Liquids Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume on Non-Operated Eagle Ford Assets				13
Subsequent Event [Member] | Drilling Rig Leasing Contracts [Member]
Other Commitments [Line Items]
Contractual Obligation | $			$ 23.7
Early Termination Penalty for Rig Contract Cancellation | $			$ 15.1

Compensation Plans (Details)

Compensation Plans (Details)	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 26, 2017USD ($)shares	Jun. 30, 2017USD ($)shares	Jun. 30, 2016USD ($)shares	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $				$ 9,813,000	$ 13,915,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				3 years
Stock-based compensation expense | $		$ 1,700,000	$ 3,000,000	$ 4,200,000	5,900,000
Unrecognized stock based compensation expense | $		10,600,000		$ 10,600,000
Performance Shares [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier Applied to PSU Awards at Settlement				0
Performance Shares [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier Applied to PSU Awards at Settlement				2
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $		2,100,000	$ 3,300,000	$ 4,600,000	$ 6,500,000
Unrecognized stock based compensation expense | $		$ 9,800,000		$ 9,800,000
Subsequent Event [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier Applied to PSU Awards at Settlement	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	977,731
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Total Fair Value | $	$ 15,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	0
Subsequent Event [Member] | 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, Grants in Period	1,010,298
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Total Fair Value | $	$ 16,800,000
Restricted Stock, Shares Issued Net of Shares for Tax Withholdings	169,891
Shares Paid for Tax Withholding for Share Based Compensation	74,060
Stock Issued During Period, Shares, Share-based Compensation, Gross	243,951
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate		15.00%		15.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription | $		$ 25,000		$ 25,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent				85.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans		123,678	140,853
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Share-based Compensation, Gross		71,573	53,473
Director [Member] | 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, Grants in Period		8,794

Pension Benefits (Details)

Pension Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Components of Net Periodic Benefit Costs for Both Pension Plans
Service cost	$ 1,269	$ 2,113	$ 3,319	$ 4,100
Interest cost	617	830	1,344	1,454
Expected return on plan assets that reduces periodic pension costs	(563)	(573)	(1,122)	(1,118)
Amortization of prior service costs	5	5	9	9
Amortization of net actuarial loss	253	419	649	791
Net periodic benefit cost	$ 1,581	$ 2,794	$ 4,199	$ 5,236

Pension Benefits Pension Narrat

Pension Benefits Pension Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)
Pension Narrative [Abstract]
Pension And Other Post-retirement Benefit Plans, Gain (Loss) Amortization Threshold	10.00%
Pension and Other Postretirement Benefit Contributions	$ 7

Earnings per Share (Details)

Earnings per Share (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017USD ($)$ / sharesshares	Jun. 30, 2016USD ($)$ / sharesshares	Jun. 30, 2017USD ($)$ / sharesshares	Jun. 30, 2016USD ($)$ / sharesshares	Dec. 31, 2016USD ($)
Earnings per share
Capped Call, Cap Price | $ / shares	$ 60		$ 60
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	44	155	59	70
Calculation of basic and diluted earnings per share
Net loss | $	$ (119,907)	$ (168,681)	$ (45,473)	$ (515,891)
Basic weighted-average common shares outstanding	111,277	68,102	111,274	68,090
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	0	0	0
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities, Treasury Stock Method	0	0	0	0
Diluted weighted-average common shares outstanding	111,277	68,102	111,274	68,090
Basic net income (loss) per common share | $ / shares	$ (1.08)	$ (2.48)	$ (0.41)	$ (7.58)
Diluted net income (loss) per common share | $ / shares	$ (1.08)	$ (2.48)	$ (0.41)	$ (7.58)
Minimum [Member] | Performance Shares [Member]
Earnings per share
Multiplier Applied to PSU Awards at Settlement			0
Maximum [Member] | Performance Shares [Member]
Earnings per share
Multiplier Applied to PSU Awards at Settlement			2
Convertible Debt [Member] | 1.50% Senior Convertible Notes Due 2021 [Domain]
Earnings per share
Debt Instrument, Face Amount | $	$ 172,500		$ 172,500		$ 172,500
Debt Instrument, Convertible, Conversion Price | $ / shares	$ 40.50		$ 40.50

Derivative Financial Instrume38

Derivative Financial Instruments (Details) bbl in Thousands, MMBTU in Thousands		Aug. 01, 2017$ / Barrelsbbl	Jun. 30, 2017MMBTU$ / EnergyContent$ / Barrelsbbl		Dec. 31, 2016MMBTU$ / EnergyContent
NYMEX Oil Swap Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			1,340
Derivative, Swap Type, Average Fixed Price | $ / Barrels			46.66
NYMEX Oil Swap Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			1,254
Derivative, Swap Type, Average Fixed Price | $ / Barrels			46.35
NYMEX Oil Swap Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			1,493
Derivative, Swap Type, Average Fixed Price | $ / Barrels			46.82
NYMEX Oil Swap Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			4,087
NYMEX Oil Collar Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			583
Derivative, Floor Price | $ / Barrels			45
Derivative, Cap Price | $ / Barrels			54.05
NYMEX Oil Collar Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			1,086
Derivative, Floor Price | $ / Barrels			47.51
Derivative, Cap Price | $ / Barrels			56.05
NYMEX Oil Collar Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			5,030
Derivative, Floor Price | $ / Barrels			50
Derivative, Cap Price | $ / Barrels			58.07
NYMEX Oil Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			3,128
Derivative, Floor Price | $ / Barrels			50
Derivative, Cap Price | $ / Barrels			58.84
NYMEX Oil Collar Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			9,827
Oil Basis Swap Contract Third Quarter 2017 [Domain]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			566
Derivative, Swap Type, Average Fixed Price | $ / Barrels	[1]		(1.62)
Oil Basis Swap Contract Fourth Quarter 2017 [Domain]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			1,798
Derivative, Swap Type, Average Fixed Price | $ / Barrels	[1]		(1.52)
Oil Basis Swap Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			6,868
Derivative, Swap Type, Average Fixed Price | $ / Barrels	[1]		(1.39)
Oil Basis Swap Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			3,963
Derivative, Swap Type, Average Fixed Price | $ / Barrels	[1]		(1.45)
Oil Basis Swap [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			13,195
Gas Swaps Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			4.01
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU			23,657
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | MMBTU			0
Derivative, Swap Type, Average Fixed Price, Purchased Volumes | $ / EnergyContent			0
Derivative, Nonmonetary Notional Amount, Energy Measure, Net of Purchased Volumes | MMBTU			23,657
Gas Swaps Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			3.98
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU			22,001
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | MMBTU			0
Derivative, Swap Type, Average Fixed Price, Purchased Volumes | $ / EnergyContent			0
Derivative, Nonmonetary Notional Amount, Energy Measure, Net of Purchased Volumes | MMBTU			22,001
Gas Swaps Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			3.41
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU			93,014
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | MMBTU	[2]		(30,606)
Derivative, Swap Type, Average Fixed Price, Purchased Volumes | $ / EnergyContent			4.27
Derivative, Nonmonetary Notional Amount, Energy Measure, Net of Purchased Volumes | MMBTU			62,408
Gas Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			3.76
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU			41,394
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | MMBTU	[2]		(24,415)
Derivative, Swap Type, Average Fixed Price, Purchased Volumes | $ / EnergyContent			4.34
Derivative, Nonmonetary Notional Amount, Energy Measure, Net of Purchased Volumes | MMBTU			16,979
Gas Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	[3]		180,066
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | MMBTU			(55,021)	[2],[3]	(55,021)
Derivative, Nonmonetary Notional Amount, Energy Measure, Net of Purchased Volumes | MMBTU	[3]		125,045
Gas Swaps Contract 2017 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent					4.43
Derivative, Nonmonetary Notional Amount, Energy Measure, Sold Volumes | MMBTU					38,600
IF El Paso Permian [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps			1.00%
IF HSC [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps			97.00%
IF NNG Ventura [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps			2.00%
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			906
Derivative, Swap Type, Average Fixed Price | $ / Barrels			9.48
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			966
Derivative, Swap Type, Average Fixed Price | $ / Barrels			9.65
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			4,017
Derivative, Swap Type, Average Fixed Price | $ / Barrels			11
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			3,112
Derivative, Swap Type, Average Fixed Price | $ / Barrels			12.27
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			539
Derivative, Swap Type, Average Fixed Price | $ / Barrels			11.13
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			9,540
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			588
Derivative, Swap Type, Average Fixed Price | $ / Barrels			21.91
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			550
Derivative, Swap Type, Average Fixed Price | $ / Barrels			21.91
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			2,021
Derivative, Swap Type, Average Fixed Price | $ / Barrels			23.38
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			214
Derivative, Swap Type, Average Fixed Price | $ / Barrels			22.66
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			3,373
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			163
Derivative, Swap Type, Average Fixed Price | $ / Barrels			32.42
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			149
Derivative, Swap Type, Average Fixed Price | $ / Barrels			32.34
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			225
Derivative, Swap Type, Average Fixed Price | $ / Barrels			33.99
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			537
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			140
Derivative, Swap Type, Average Fixed Price | $ / Barrels			33.28
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			128
Derivative, Swap Type, Average Fixed Price | $ / Barrels			33.23
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			188
Derivative, Swap Type, Average Fixed Price | $ / Barrels			33.56
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			456
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			222
Derivative, Swap Type, Average Fixed Price | $ / Barrels			48.43
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2017 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			203
Derivative, Swap Type, Average Fixed Price | $ / Barrels			48.41
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			305
Derivative, Swap Type, Average Fixed Price | $ / Barrels			48.62
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume			730
Subsequent Event [Member] | NYMEX Oil Swap Contract 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume		1,979
Derivative, Swap Type, Average Fixed Price | $ / Barrels		50.37
[1]	Represents the price differential between WTI prices at Midland, Texas and WTI prices at Cushing, Oklahoma.
[2]	During 2016, the Company restructured certain of its natural gas derivative contracts by buying fixed price volumes to offset existing 2018 and 2019 fixed price swap contracts totaling 55.0 million MMBtu. The Company then entered into new 2017 fixed price swap contracts totaling 38.6 million MMBtu with a contract price of $4.43 per MMBtu. No other cash or other consideration was included as part of the restructuring.
[3]	Total net volumes of natural gas swaps are comprised of IF El Paso Permian (1%), IF HSC (97%), and IF NNG Ventura (2%).

Derivative Financial Instrume39

Derivative Financial Instruments Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2017		Dec. 31, 2016
Fair value of derivative assets and liabilities
Derivative, Fair Value, Net	$ 61,900		$ (91,700)
Derivative asset current	85,962		54,521
Derivative asset noncurrent	82,194		67,575
Derivative Asset, Fair Value, Gross Asset	168,156		122,096
Derivative liability current	36,296		115,464
Derivatives liability noncurrent	69,915		98,340
Derivative Liability, Fair Value, Gross Liability	106,211		213,804
Derivatives not designated as hedging instruments
Fair value of derivative assets and liabilities
Derivative asset current	85,962		54,521
Derivative asset noncurrent	82,194		67,575
Derivative liability current	36,296		115,464
Derivatives liability noncurrent	69,915		98,340
Fair Value, Inputs, Level 2 [Member] | Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member]
Fair value of derivative assets and liabilities
Derivative Asset, Fair Value, Gross Asset	168,156	[1]	122,096	[2]
Derivative Liability, Fair Value, Gross Liability	$ 106,211	[1]	$ 213,804	[2]
[1]	This represents a financial asset or liability that is measured at fair value on a recurring basis.
[2]	This represents a financial asset or liability that is measured at fair value on a recurring basis.

Derivative Financial Instrume40

Derivative Financial Instruments Offsetting of Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Offsetting of Derivative Assets and Liabilities [Abstract]
Derivative Asset, Fair Value, Gross Asset	$ 168,156	$ 122,096
Derivative Liability, Fair Value, Gross Liability	(106,211)	(213,804)
Derivative Asset, Not Offset, Policy Election Deduction	(64,628)	(118,080)
Derivative Liability, Not Offset, Policy Election Deduction	64,628	118,080
Derivative Asset, Fair Value, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	103,528	4,016
Derivative Liability, Fair Value, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	$ (41,583)	$ (95,724)

Derivative Financial Instrume41

Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Document Fiscal Year Focus			2,017
Derivative settlement (gain) loss	$ (16,303)	$ (101,710)	$ (16,310)	$ (248,738)
Net derivative (gain) loss	(55,189)	163,351	(169,963)	149,123
Oil Contracts [Member]
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative settlement (gain) loss	2,754	(72,164)	11,838	(172,156)
Net derivative (gain) loss	(38,194)	60,773	(87,784)	50,341
Gas Contracts [Member]
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative settlement (gain) loss	(21,751)	(31,439)	(39,257)	(72,492)
Net derivative (gain) loss	(6,038)	62,489	(50,506)	38,466
NGL Contracts [Member]
Gain and loss from derivative cash settlements and changes in fair value of derivative contracts
Derivative settlement (gain) loss	2,694	1,893	11,109	(4,090)
Net derivative (gain) loss	$ (10,957)	$ 40,089	$ (31,673)	$ 60,316

Derivative Financial Instrume42

Derivative Financial Instruments Credit Facility and Derivative Counterparties (Details)	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Percentage of Proved Property Secured for Credit Facility Borrowing	90.00%

Fair Value Measurements Fair 43

Fair Value Measurements Fair Value (Details) - USD ($) $ in Thousands		Jun. 30, 2017		Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 168,156		$ 122,096
Property, Plant and Equipment, Net		5,346,411		6,081,354
Derivative Liability, Fair Value, Gross Liability		106,211		213,804
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	[1]			0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	[1]			0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	[1]			88,205
Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	[2]	0	[3]
Derivative Liability, Fair Value, Gross Liability		0	[2]	0	[3]
Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		168,156	[2]	122,096	[3]
Derivative Liability, Fair Value, Gross Liability		106,211	[2]	213,804	[3]
Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	[2]	0	[3]
Derivative Liability, Fair Value, Gross Liability		$ 0	[2]	$ 0	[3]
[1]	This represents a non-financial asset that is measured at fair value on a nonrecurring basis.
[2]	This represents a financial asset or liability that is measured at fair value on a recurring basis.
[3]	This represents a financial asset or liability that is measured at fair value on a recurring basis.

Fair Value Measurements Long-te

Fair Value Measurements Long-term Debt (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
6.50% Senior Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount	[1]	$ 344,611
6.125% Senior Notes Due 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount		561,796
6.50% Senior Notes Due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount		394,985
5% Senior Notes Due 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount		500,000
5.625% Senior Notes Due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount		500,000
6.75% Senior Notes Due 2026 [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Face Amount		$ 500,000
Senior Notes [Member] | 6.50% Senior Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%
Debt Instrument, Face Amount		$ 344,611	$ 346,955
Long-term Debt, Fair Value		$ 338,794	354,546
Senior Notes [Member] | 6.125% Senior Notes Due 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.125%
Debt Instrument, Face Amount		$ 561,796	561,796
Long-term Debt, Fair Value		$ 536,347	570,925
Senior Notes [Member] | 6.50% Senior Notes Due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%
Debt Instrument, Face Amount		$ 394,985	394,985
Long-term Debt, Fair Value		$ 377,211	403,134
Senior Notes [Member] | 5% Senior Notes Due 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.00%
Debt Instrument, Face Amount		$ 500,000	500,000
Long-term Debt, Fair Value		$ 445,465	475,975
Senior Notes [Member] | 5.625% Senior Notes Due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.625%
Debt Instrument, Face Amount		$ 500,000	500,000
Long-term Debt, Fair Value		$ 449,335	485,000
Senior Notes [Member] | 6.75% Senior Notes Due 2026 [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.75%
Debt Instrument, Face Amount		$ 500,000	500,000
Long-term Debt, Fair Value		$ 479,840	516,565
Convertible Debt [Member] | 1.50% Senior Convertible Notes Due 2021 [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.50%
Debt Instrument, Face Amount		$ 172,500	172,500
Long-term Debt, Fair Value		$ 154,612	$ 202,189
[1]	During the first quarter of 2017, the Company repurchased a total of $2.3 million in aggregate principal amount of 6.50% Senior Notes due 2021 in open market transactions at a slight premium. The Company canceled all of these repurchased Senior Notes upon cash settlement.

Fair Value Measurements Proved

Fair Value Measurements Proved and Unproved Oil and Gas Properties (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended		12 Months Ended
		Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net		$ 5,346,411				$ 5,346,411		$ 6,081,354
Impairment of Proved Oil and Gas Properties		3,806		$ 0		$ 3,806	$ 269,785
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down				$ (49,500)	$ 68,300
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	[1]							$ 88,205
Oil and Gas Properties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast						5 years
Oil and Gas Properties [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate						10.00%		10.00%
Oil and Gas Properties [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate						15.00%		15.00%
Divide County Disposal Group [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Proved Oil and Gas Properties						$ 526,500
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down		$ 166,900	$ 359,600
[1]	This represents a non-financial asset that is measured at fair value on a nonrecurring basis.