Supplemental Oil and Natural Gas Information - Standardized Measure of Discounted Net Future Cash Flows (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Net Cash Flows [Abstract]
Future cash inflows (total revenues)	$ 6,730,000	$ 4,750,238	$ 1,143,142
Future production costs	(2,964,098)	(2,332,310)	(725,724)
Future development costs (capital costs)	(855,932)	(879,399)	(116,988)
Future income tax expense	(136,472)
Future net cash flows	2,773,498	1,538,529	300,430
10% annual discount for estimated timing of cash flows	(1,444,188)	(808,843)	(94,449)
Standardized measure of Discounted Future Net Cash Flow	$ 1,329,310	$ 729,686	$ 205,981	$ 212,865