Commitments and Contingencies, Asset Retirement Obligations (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		$ 399		$ 324
Amounts Incurred		0		26	[1]
Amounts Settled		0		(3)	[2]
Accretion		16		14
Cash Flow Revisions		7	[3]	38	[4]
Ending balance		422	[5]	399
Electric Plant Steam and Other Production Ash Containment
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		137		100
Amounts Incurred	[1]			0
Amounts Settled	[2]			0
Accretion		5		4
Cash Flow Revisions		10	[3]	33	[4]
Ending balance		152	[5]	137
Electric Plant Wind Production
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		40		16
Amounts Incurred	[1]			26
Amounts Settled	[2]			(3)
Accretion		2		1
Cash Flow Revisions		0	[3]	0	[4]
Ending balance		42	[5]	40
Electric Plant Electric Distribution
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		15		14
Amounts Incurred	[1]			0
Amounts Settled	[2]			0
Accretion		1		1
Cash Flow Revisions		0	[3]	0	[4]
Ending balance		16	[5]	15
Natural Gas Plant Gas Transmission and Distribution
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		203		190
Amounts Incurred	[1]			0
Amounts Settled	[2]			0
Accretion		9		8
Cash Flow Revisions		(8)	[3]	5	[4]
Ending balance		204	[5]	203
Natural Gas Plant Other
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		3		3
Amounts Incurred	[1]			0
Amounts Settled	[2]			0
Accretion		0		0
Cash Flow Revisions		5	[3]	0	[4]
Ending balance		8	[5]	3
Common and Other Property Common Miscellaneous
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		1		1
Amounts Incurred	[1]			0
Amounts Settled	[2]			0
Accretion		(1)		0
Cash Flow Revisions		0	[3]	0	[4]
Ending balance		$ 0	[5]	$ 1

[1] Amounts incurred related to the Cheyenne Ridge wind farm placed in service in 2020.

[2] Amounts settled related to removal of wind facilities.

[3] In 2021, AROs were revised for changes in timing and estimates of cash flows. Revisions in steam, hydro, and other production AROs primarily related to changes in cost estimates for remediation of ash containment facilities. Changes in gas transmission and distribution AROs were primarily related to changes in labor rates coupled with increased gas line mileage and number of services.

[4] In 2020, AROs were revised for changes in timing and estimates of cash flows. Revisions in steam, hydro, and other production AROs primarily related to changes in cost estimates for remediation of ash containment facilities.

[5] There were no ARO amounts incurred or settled in 2021.