Supplemental Gas and Oil Information (Unaudited) Estimated Quantities of Proved Gas and Oil Reserves (Details) MMBoe in Millions, MMBbls in Millions, Bcf in Billions		12 Months Ended
		Dec. 31, 2020 MMBoe MMBbls Bcf	Dec. 31, 2019 MMBoe Bcf MMBbls		Dec. 31, 2018 MMBoe MMBbls Bcf
Oil [Member]
Reserve Quantities [Line Items]
Proved reserves balance, beginning balance		254.9	339.1		320.5
Revisions of previous estimates		2.7	(94.9)		2.1	[1]
Extensions and discoveries		0.1	33.6		57.1
Purchase of reserves in place			3.6		8.2
Sale of reserves in place		(0.1)	(4.9)		(24.9)
Production		(19.7)	(21.6)		(23.9)
Proved reserves balance, ending balance		237.9	254.9		339.1
Proved undeveloped reserves, beginning balance		137.4	205.5		204.5
Proved undeveloped reserve, ending balance		136.7	137.4		205.5
Proved developed reserves, beginning balance		117.5	133.6		116.0
Proved developed reserves, ending balance		101.2	117.5		133.6
Gas [Member]
Reserve Quantities [Line Items]
Proved reserves balance, beginning balance | Bcf		373.3	1,487.6		1,793.6
Revisions of previous estimates | Bcf		27.6	(23.0)		314.0	[1]
Extensions and discoveries | Bcf		0.2	40.0		56.5
Purchase of reserves in place | Bcf			4.0		7.9
Sale of reserves in place | Bcf		(0.3)	(1,102.2)		(544.8)
Production | Bcf		(32.5)	(33.1)		(139.6)
Proved reserves balance, ending balance | Bcf		368.3	373.3		1,487.6
Proved undeveloped reserves, beginning balance | Bcf		156.3	1,105.3		1,138.1
Proved undeveloped reserve, ending balance | Bcf		183.3	156.3		1,105.3
Proved developed reserves, beginning balance | Bcf		217.0	382.3		655.5
Proved developed reserves, ending balance | Bcf		185.0	217.0		382.3
Natural Gas Liquids [Member]
Reserve Quantities [Line Items]
Proved reserves balance, beginning balance		65.2	71.2		65.2
Revisions of previous estimates		4.1	(8.7)		6.7	[1]
Extensions and discoveries		0.0	7.4		9.8
Purchase of reserves in place			0.7		1.3
Sale of reserves in place		0.0	(0.3)		(7.1)
Production		(5.2)	(5.1)		(4.7)
Proved reserves balance, ending balance		64.1	65.2		71.2
Proved undeveloped reserves, beginning balance		28.5	39.7		37.3
Proved undeveloped reserve, ending balance		32.1	28.5		39.7
Proved developed reserves, beginning balance		36.7	31.5		27.9
Proved developed reserves, ending balance		32.0	36.7		31.5
Barrels of oil equivalent production [Member]
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves, beginning balance | MMBoe	[2]	382.3	658.2		684.7
Revisions of previous estimates | MMBoe		11.4	(107.3)	[2]	61.0	[1],[2]
Extensions and discoveries | MMBoe	[2]	0.2	47.6		76.3
Purchase of reserves in place | MMBoe	[2]		4.9		10.9
Sale of reserves in place | MMBoe	[2]	(0.2)	(188.9)		(122.8)
Production | MMBoe	[2]	(30.3)	(32.2)		(51.9)
Proved developed and undeveloped reserves, ending balance | MMBoe	[2]	363.4	382.3		658.2
Proved undeveloped reserves, beginning balance | MMBoe		191.9	429.3		431.6
Proved undeveloped reserves, ending balance | MMBoe		199.4	191.9		429.3
Proved developed reserves, beginning balance | MMBoe		190.4	228.9		253.1
Proved developed reserves, ending balance | MMBoe		164.0	190.4		228.9
Pricing Revisions [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe		41.4	17.0		17.3
Performance Revisions [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe			13.7		8.7
Positive revisions [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe		63.0	4.6
Operating Cost Revisions [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe		4.2			11.7
Other Revisions [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe		2.5	10.9
Development plan change [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe			44.5		23.4
PUD Removals [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe		16.9	25.8
Positive PUD Revisions [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates | MMBoe		58.8

[1] Revisions of previous estimates in 2018 totaling 61.0 MMboe of positive revisions include 23.4 MMboe of other revisions, primarily related to changing our development plans in the Haynesville/Cotton Valley; 17.3 MMboe of positive revisions related to pricing, primarily driven by higher oil prices; 11.7 MMboe of positive revisions related to lower operating costs; and 8.7 MMboe of positive performance revisions. (2)Extensions and discoveries in 2018 primarily related to new well completions and associated new PUD locations in the Permian Basin. (3)Purchase of reserves in place in 2018 primarily relates to the additional acquisitions in the Permian Basin as discussed in Note 3 – Acquisitions and Divestitures. (4)Sale of reserves in place in 2018 was primarily related to QEP's Uinta Basin Divestiture as discussed in Note 3 – Acquisitions and Divestitures. (5)Revisions of previous estimates in 2019 totaling 107.3 MMboe of negative revisions includes 44.5 MMboe of negative PUD revisions as a result of changes to the development sequence in the Permian Basin, to maximize capital efficiency (see offset in extensions and discoveries footnote 6 below); 25.8 MMboe of PUD removals, primarily in the Williston Basin, that will not be developed within five years of the initial date of booking due to the reduction in future capital expenditures; 17.0 MMboe of negative revisions related to pricing, primarily driven by lower oil prices; 13.7 MMboe of negative performance revisions, primarily associated with updated volume projections for high-density wells and certain undrilled locations in the Permian Basin; 10.9 MMboe of other negative revisions, partially offset by 4.6 MMboe of positive revisions related to lower operating costs. (6)Extensions and discoveries in 2019 primarily related to new PUD locations in the Permian Basin due to changes in the development sequence in the Permian Basin to maximize capital efficiency. See partial offset in revisions to previous estimates in footnote 9 above. (7)Purchase of reserves in place in 2019 primarily relates to the additional acquisitions in the Permian Basin as discussed in Note 3 – Acquisitions and Divestitures. (8)Sale of reserves in place in 2019 was primarily related to QEP's Haynesville Divestiture as discussed in Note 3 – Acquisitions and Divestitures. (9)Revisions of previous estimates in 2020 totaling 11.4 MMboe of positive revisions includes 63.0 MMboe of positive revisions, of which 58.8 MMboe was positive PUD revisions, as a result of changes in development sequence in the Permian Basin to maximize Free Cash Flow. Additionally, there were 4.2 MMboe of positive revisions related to lower operating costs and 2.5 MMboe of other positive revisions, partially offset by 41.4 MMboe of negative price revisions, primarily driven by lower oil prices and 16.9 MMboe of PUD removals, primarily in Permian Basin, that will not be developed within five years of the initial date of booking due to the reduction in future capital expenditures. (10)Generally, gas consumed in operations was excluded from reserves, however, in some cases, produced gas consumed in operations was included in reserves when the volumes replaced fuel purchases.

[2] Stand