Commitments and Contingencies, Asset Retirement Obligations (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	[1]	$ 18	[2],[3]	$ 18
Accretion	[1]			1
Cash Flow Revisions		4	[2],[4]	(1)	[1]
Ending balance	[2]	22	[5]	18	[1],[3]
Electric Plant Electric Distribution
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		5	[3]	5
Accretion				0
Cash Flow Revisions		0	[4]	0
Ending balance		5	[5]	5	[3]
Electric Plant Steam Production Asbestos
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		4	[3]	4
Accretion				0
Cash Flow Revisions		4	[4]	0
Ending balance		8	[5]	4	[3]
Natural Gas Plant Gas Distribution
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance		9	[3]	9
Accretion				1
Cash Flow Revisions		0	[4]	(1)
Ending balance		$ 9	[5]	$ 9	[3]

[1] Included in other long-term liabilities balance in the consolidated balance sheet

[2] Included in other long-term liabilities balance in the consolidated balance sheet.

[3] There were no ARO amounts incurred or settled in 2019.

[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 2020.