Net Property and Equipment - Schedule of Net Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment, Net [Abstract]
Proved crude oil and natural gas properties	$ 21,362,199	$ 19,802,395
Unproved crude oil and natural gas properties	365,413	429,562
Service properties, equipment and other	290,111	301,788
Total property and equipment	22,017,723	20,533,745
Accumulated depreciation, depletion and amortization	(9,083,934)	(7,652,518)
Net property and equipment	$ 12,933,789	$ 12,881,227