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Asset Retirement Obligations - MEC - Asset Retirement Obligations By Type (Details) - USD ($)
$ in Millions
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Asset Retirement Obligations By Type [Line Items]      
Regulatory liabilities $ 7,214 $ 7,475  
Asset retirement obligations 1,340 1,341 $ 1,272
Quad Cities Station      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 427 376  
Fossil fuel facilities      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 466 529  
Wind generating facilities      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 299 273  
Other      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 109 123  
MEC      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 787 818 $ 839
MEC | Quad Cities Station      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 427 376  
MEC | Fossil fuel facilities      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 161 255  
MEC | Wind generating facilities      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 197 185  
MEC | Other      
Asset Retirement Obligations By Type [Line Items]      
Asset retirement obligations 2 2  
Quad Cities Station | MEC      
Asset Retirement Obligations By Type [Line Items]      
Quad Cities Station nuclear decommissioning trust funds 768 676  
Cost of removal      
Asset Retirement Obligations By Type [Line Items]      
Regulatory liabilities 2,424 2,435  
Cost of removal | MEC      
Asset Retirement Obligations By Type [Line Items]      
Regulatory liabilities $ 394 $ 466