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			2017
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

This is focus fiscal year of the document report in CCYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006.

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- Definition

Realized gain (loss) recognized in earnings from the settlement of derivative instruments not designated as hedges.

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- Definition

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959

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