Asset Impairment - Summary of Impairments Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 220,025	$ 6,583
Central Basin Platform
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	187,043	0
Delaware Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	21,288	4,330
San Juan Basin
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	7,519	0
Permian Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	4,135	2,005
San Juan Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 40	$ 248