Income Tax - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax asset:
Oil and gas properties and equipment	$ 93,854	$ 193,095	$ 235,884
Federal tax loss carryforwards	114,652	145,628	61,006
Derivative instruments and other	1,064	16,829
State effect of deferreds			540
Other, net	4,639	4,259	3,434
Deferred tax asset	214,209	359,811	300,864
Valuation allowance	(213,800)	(359,098)	(287,786)
Net deferred tax assets	409	713	13,078
Deferred tax liability:
Derivative instruments and other			12,054
Other, net	409	713	484
Net deferred tax liability	$ 409	$ 713	12,538
Net deferred tax asset			$ 540