Supplemental Crude Oil and Natural Gas Information - Standardized Measure of Discounted Future Net Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Crude Oil and Natural Gas Information [Abstract]
Discount factor utilized as standardized measure for future net cash flows	10.00%
Future cash inflows	$ 61,510,432	$ 42,574,897	$ 31,008,587
Future production costs	(16,139,001)	(11,159,362)	(9,175,410)
Future development and abandonment costs	(9,706,114)	(6,487,097)	(6,452,647)
Future income taxes	(6,012,439)	(3,488,755)	(3,018,839)
Future net cash flows	29,652,878	21,439,683	12,361,691
10% annual discount for estimated timing of cash flows	(13,968,061)	(10,969,506)	(6,851,468)
Standardized measure of discounted future net cash flows	$ 15,684,817	$ 10,470,177	$ 5,510,223	$ 6,476,284