Supplemental Crude Oil and Natural Gas Information - Schedule of Proved Crude Oil and Natural Gas Reserves (Detail)	12 Months Ended
	Dec. 31, 2018 MBoe MMcf MBbls	Dec. 31, 2017 MBoe MMcf MBbls	Dec. 31, 2016 MBoe MMcf MBbls	Dec. 31, 2015 MBoe
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserve, Net (Energy) | MBoe	1,522,365	1,330,995	1,274,864	1,225,811
Changes in Proved Reserves [Roll Forward]
Revisions of previous estimates | MBoe	(269,253)	(82,012)	(110,474)
Extensions, discoveries, and other additions | MBoe	565,030	240,206	249,430
Proved Developed and Undeveloped Reserve, Production (Energy) | MBoe	108,839	88,562	79,390
Sales of minerals in place, Total | MBoe	(8,011)	(15,197)	(10,513)
Purchases of minerals in place, Total | MBoe	12,443	1,696	0
Percent of proved crude oil reserve estimates prepared by external reserve engineers	98.00%	96.00%	99.00%
Natural Gas [Member]
Changes in Proved Reserves [Roll Forward]
Proved reserves at beginning of period | MMcf	4,140,281	3,789,818	3,151,786
Revisions of previous estimates | MMcf	(1,153,555)	(25,390)	(63,057)
Extensions, discoveries and other additions | MMcf	1,871,777	661,867	911,062
Production | MMcf	(284,730)	(228,159)	(195,240)
Sales of minerals in place | MMcf	(35,142)	(64,989)	(14,733)
Purchases of minerals in place | MMcf	52,983	7,134	0
Proved reserves at end of period | MMcf	4,591,614	4,140,281	3,789,818
Crude Oil [Member]
Changes in Proved Reserves [Roll Forward]
Proved reserves at beginning of period | MBbls	640,949	643,228	700,514
Revisions of previous estimates | MBbls	(76,994)	(77,779)	(99,966)
Extensions, discoveries and other additions | MBbls	253,066	129,895	97,587
Production | MBbls	(61,384)	(50,536)	(46,850)
Sales of minerals in place | MBbls	(2,154)	(4,365)	(8,057)
Purchases of minerals in place | MBbls	3,613	506	0
Proved reserves at end of period | MBbls	757,096	640,949	643,228