Supplemental Information on Natural Gas and Oil Exploration, Development and Production Activities (Unaudited) - Additional Information (Detail) Bcfe in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2019 USD ($) MMcfe Bcfe $ / MMBTU $ / bbl $ / Mcf MMcf MBbls	Dec. 31, 2018 MMcfe $ / MMBTU $ / bbl $ / Mcf MMcf MBbls	Dec. 31, 2017 MMcfe $ / MMBTU $ / bbl $ / Mcf MMcf MBbls	Dec. 31, 2016 MMcfe MMcf MBbls
Reserve Quantities [Line Items]
Percentage of proved resources reviewed by consultants		90.00%
Proved reserve and pretax present value of reserve discounted		10.00%
Variance in reserve estimates		less than 5%.
Scheduled to be drilling period maximum for undeveloped reserves		scheduled to be drilled within five years
Reserve additions attributable to natural gas		83.00%	72.00%	82.00%
Proved undeveloped reserves dropped		601,300	379,000	668,000
Revision of negative pricing		17,800
Revision of positive pricing and performance			957,000
Revisions of positive pricing			154,000	46,000
Improved recoveries				597,000
Cost spent on undeveloped reserves transferred to developed reserves | $		$ 340.4
Estimated future development costs over next five years | $		$ 2,900.0
Proved undeveloped reserves reported for more than five years | Bcfe		86
Crude Oil and NGL
Reserve Quantities [Line Items]
Benchmark price used for calculating average realized prices | $ / bbl		55.73	65.55	51.19
Crude Oil and Condensate
Reserve Quantities [Line Items]
Estimate reserve information average realized prices | $ / bbl		49.24	59.96	45.73
Proved developed and undeveloped reserves | MBbls		74,532	85,856	69,854	70,252
NGLs
Reserve Quantities [Line Items]
Estimate reserve information average realized prices | $ / bbl		17.32	25.22	17.84
Proved developed and undeveloped reserves | MBbls		938,236	921,594	763,264	630,066
Natural Gas
Reserve Quantities [Line Items]
Estimate reserve information average realized prices | $ / Mcf		2.38	2.98	2.60
Proved developed and undeveloped reserves | MMcf		12,114,977	12,027,702	10,263,649	7,870,416
Natural Gas, Per Thousand Cubic Feet
Reserve Quantities [Line Items]
Benchmark price used for calculating average realized prices | $ / MMBTU		2.58	3.10	2.98
Natural Gas Equivalents
Reserve Quantities [Line Items]
Proved reserves from drilling activities and evaluations of proved areas	[1]	1,161,274	3,143,898	3,487,519
Proved developed and undeveloped reserve balances	[1]	18,191,583	18,072,406	15,262,361	12,072,322
Revisions of previous estimates	[1]	303,068	731,735	506,919
Revision of positive performance		922,200		532,000
Ethane and Natural Gas Equivalents
Reserve Quantities [Line Items]
Proved developed and undeveloped reserve balances		2,102,000	2,075,000	1,596,000
Proved developed and undeveloped reserves | MBbls		475,000.0	468,900	360,600
Maximum
Reserve Quantities [Line Items]
Statement that reserve estimates differ from auditors		0.10

[1] Oil and NGLs volumes are converted to mcfe at the rate of one barrel equals six mcf based upon the approximate relative energy content of oil to natural gas, which is not indicative of the relationship between oil and natural gas prices.