Commitments and Contingencies Regulatory Plant Decommissioning Recovery (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Percentage Of Total Obligation For Decommissioning Expected To Be Funded By External Funds		100.00%
Assumed annual escalation rate during operations and radiological portion of decommissioning		4.36%
Assumed annual escalation rate during independent fuel storage installation and site restoration portion of decommissioning		3.36%
Average risk-free interest rate		1.96%		1.64%
Asset Retirement Obligation		$ 2,585	[1]	$ 2,350		$ 2,280
Nuclear Decommissioning Expense	[2],[3]	22		20		20
Approved annual accrual for decommissioning costs		14		14		14
Nuclear Plant [Member]
Public Utilities, General Disclosures [Line Items]
Discounted decommissioning cost obligation		6,554		7,024
Differences in Discount Rate and Market Risk Premium		(2,209)		(2,628)
Operating and Maintenance Costs Not Included for GAAP		(1,584)		(1,734)
ARO differences between 2020 and 2014 cost studies		(705)		(705)
Asset Retirement Obligation		$ 2,056	[1]	1,957		$ 2,068
Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Assumed after tax rate of return used to determine funding for external decommissioning trust fund		5.23%
Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Assumed after tax rate of return used to determine funding for external decommissioning trust fund		6.30%
Nuclear Decommissioning Fund [Member] | Fair Value Measured on a Recurring Basis | Estimate of Fair Value Measurement [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Decommissioning Cost Obligation From Most Recently Approved Study		$ 3,012		3,012
Effect Of Escalating Costs To Current Year Dollars		1,006		844
Estimated Decommissioning Cost Obligation In Current Dollars		4,018		3,856
Effect Of Escalating Costs To Payment Date		7,187		7,349
Estimated Future Decommissioning Costs Undiscounted		11,205		11,205
Effect Of Discounting Obligation Using Risk Free Interest Rate		(4,651)		(4,181)
Discounted decommissioning cost obligation		6,554		7,024
Decommissioning Fund Investments		3,256	[4]	2,777	[5]
Discounted Decommissioning Obligation Compared To Assets Currently Held In Trust		$ 3,298		$ 4,247

[1] There were no ARO amounts settled in 2021.

[2] Decommissioning expense does not include depreciation of the capitalized nuclear asset retirement costs.

[3] Decommissioning expenses in 2021, 2020 and 2019 include Minnesota’s retail jurisdiction annual funding requirement of approximately $14 million.

[4] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $52 million of rabbi trust assets and miscellaneous investments.

[5] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheet, which also includes $53 million of rabbi trust assets and miscellaneous investments.