Supplemental Oil and Natural Gas Information (unaudited) - Proved Developed and Proved Undeveloped Reserves (Detail)	12 Months Ended
	Dec. 31, 2019 Bcfe Bcf MBbls	Dec. 31, 2018 Bcfe Bcf MBbls	Dec. 31, 2017 Bcfe Bcf MBbls	Dec. 31, 2016 Bcfe Bcf MBbls
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves (energy), beginning balance | Bcfe	1,864.7	1,458.6	469.4
Revisions (energy) | Bcfe	(59.6)	(42.8)	695.6
Extensions and discoveries (energy) | Bcfe	599.2	558.1	405.1
Acquisitions (energy) | Bcfe	525.5	16.3	1.9
Divestitures (energy) | Bcfe		(0.2)
Production (energy) | Bcfe	(200.0)	(125.3)	(113.4)
Proved Developed and Undeveloped Reserves (energy), ending balance | Bcfe	2,729.8	1,864.7	1,458.6
Proved developed reserves (energy) | Bcfe	1,494.2	670.7	456.0	297.8
Proved undeveloped reserves (energy) | Bcfe	1,235.6	1,194.1	1,002.6	171.6
Natural Gas [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves, beginning balance | Bcf	1,531.2	1,090.1	386.4
Revisions | Bcf	(77.0)	5.6	515.1
Extensions and discoveries | Bcf	418.7	515.8	274.4
Acquisitions | Bcf	418.9	9.9	1.6
Divestitures | Bcf		(0.2)
Production | Bcf	(154.1)	(90.0)	(87.4)
Proved Developed and Undeveloped Reserves, ending balance | Bcf	2,137.7	1,531.2	1,090.1
Proved developed reserves | Bcf	1,183.2	501.0	334.6	226.1
Proved undeveloped reserves | Bcf	954.5	1,030.2	755.5	160.4
Natural Gas Liquids [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves, beginning balance	34,730.9	41,930.6	8,675.5
Revisions	4,454.5	(8,307.5)	20,327.3
Extensions and discoveries	19,016.3	4,059.4	15,598.8
Acquisitions	14,844.0	551.4	42.6
Production	(4,686.3)	(3,503.0)	(2,713.6)
Proved Developed and Undeveloped Reserves, ending balance	68,359.4	34,730.9	41,930.6
Proved developed reserves	39,316.3	20,213.8	13,782.9	7,520.0
Proved undeveloped reserves	29,043.2	14,517.2	28,147.7	1,155.5
Oil [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves, beginning balance	20,852.1	19,480.8	5,157.7
Revisions	(1,569.8)	231.2	9,746.8
Extensions and discoveries	11,078.1	2,995.7	6,192.9
Acquisitions	2,915.2	522.2	5.8
Production	(2,950.8)	(2,377.8)	(1,622.4)
Proved Developed and Undeveloped Reserves, ending balance	30,324.8	20,852.1	19,480.8
Proved developed reserves	12,512.6	8,058.7	6,449.6	4,439.5
Proved undeveloped reserves	17,812.2	12,793.4	13,031.2	718.1