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Investments and Restricted Cash and Cash Equivalents - MEC (Details) - USD ($)
$ in Millions
Dec. 31, 2023
Dec. 31, 2022
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Total investments $ 4,039 $ 6,462
Total 9,510 11,273
Quad Cities Station nuclear decommissioning trust funds    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Nuclear decommissioning trust 767 664
MEC    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Rabbi trusts 239 215
Total investments 24 23
Total $ 1,030 $ 902
MEC | U.S. companies    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Ownership percentage 56.00% 54.00%
MEC | US Government Corporations and Agencies Securities    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Ownership percentage 33.00% 32.00%
MEC | Corporate obligations    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Ownership percentage 9.00% 11.00%
MEC | Other    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Ownership percentage 2.00% 3.00%
MEC | Quad Cities Station nuclear decommissioning trust funds    
Investments, Including Equity Method And Restricted Cash And Investments [Line Items]    
Nuclear decommissioning trust $ 767 $ 664