Acquisitions and Divestitures - Divestiture (Woodford and Mississippian Lime) (Details) $ in Thousands, Mcfe in Billions	1 Months Ended		3 Months Ended		6 Months Ended
	Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 04, 2015 USD ($)	Dec. 31, 2014 Mcfe
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of oil and gas properties		$ 21,500	$ 0	$ 21,531	$ 0	$ 21,531
Sale of oil and gas properties	$ 7,000				24,909	$ 257,698
Required purchase price of the non-producing assets if agreement not reached					$ 5,000
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							$ 260,200
Proved reserves (Bcfe) | Mcfe								227
Estimated proved reserves attributable to Sold Assets (percent of total)								57.00%