Asset Impairment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended					9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 587		$ 399,394			$ 220,612	$ 466,390
Price curve, term						5 years
Increase (decrease) in carrying amount of properties, percent						3.00%
Oil
Impaired Long-Lived Assets Held and Used [Line Items]
Increase (decrease) in carrying amount of properties, percent		(5.00%)	(19.00%)
Natural Gas
Impaired Long-Lived Assets Held and Used [Line Items]
Increase (decrease) in carrying amount of properties, percent		(4.00%)	(12.00%)
Permian Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment		$ 208,300	$ 390,200	$ 51,500	$ 4,300
Permian Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	587	4,700	9,148			$ 4,722	20,092
San Juan Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 0	$ 7,500	$ 0			$ 7,519	$ 0