Asset Impairment - Summary of Impairments Recognized (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 29	$ 0		$ 1,489	$ 220,025
Central Basin Platform
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	0	0		1,096	187,043
Delaware Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	0	0		0	21,288
San Juan Basin properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	0	0	$ 7,500	0	7,519
Permian Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	29	0	$ 4,100	393	4,135
San Juan Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 0	$ 0		$ 0	$ 40