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Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($)
$ in Millions
Mar. 31, 2019
Dec. 31, 2018
Mar. 31, 2018
Dec. 31, 2017
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents $ 234 $ 153    
Other non-current assets 0 1    
Cash and cash equivalents, including restricted amounts 267 175 $ 227 $ 204
Consumers Energy Company        
Cash and Cash Equivalents [Line Items]        
Cash and cash equivalents 37 39    
Other non-current assets 0 0    
Cash and cash equivalents, including restricted amounts $ 64 $ 56 $ 146 $ 65