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Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents $ 496 $ 168    
Restricted cash and cash equivalents 28 17    
Cash and cash equivalents, including restricted amounts 524 185 $ 861 $ 157
Consumers Energy Company        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 9 20    
Restricted cash and cash equivalents 25 15    
Cash and cash equivalents, including restricted amounts $ 34 $ 35 $ 628 $ 28