Summary of Significant Accounting Policies - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Liabilities, Current [Abstract]
Accrued drilling costs	$ 5,874	$ 7,498
Accrued interest payable	21,277	22,721
Accrued transportation costs	3,269	2,227
Accrued employee compensation	6,449	6,292
Asset retirement obligation – assets held for sale	4,557
Other	1,029	1,628
Total accrued expenses	$ 42,455	$ 40,366