Acquisitions and Divestitures - Divestitures (Woodford and Mississippian Lime Interests) (Details) $ in Thousands, Mcfe in Millions		3 Months Ended	12 Months Ended
	Jun. 04, 2015 USD ($) term	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) Mcfe	Dec. 31, 2013 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of assets		$ 21,500	$ 21,937	$ 0	$ 0
Woodford And Mississippian Lime
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from sale of a majority of interests	$ 280,000
Cash received from sale	$ 257,700
Number of renewal terms for contract operator | term	2
Contract operator term for sold assets	1 year
Proved reserves | Mcfe				227.2
Estimated proved reserves attributable to Sold Assets (percent of total)				57.00%
Gain on sale of assets			$ 23,200
Woodford And Mississippian Lime | Current Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other receivable	$ 13,900