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Financings and Capitalization (Narrative) (Details) - USD ($)
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2019
Dec. 31, 2018
Financing And Capitalization [Line Items]      
Amount available for dividend payments $ 4,900,000,000 $ 4,900,000,000  
Common stock dividends from Consumers   $ 172,000,000  
Stock offering program maximum value     $ 250,000,000
Settlement required (in shares) 424,770 424,770  
Consumers Energy Company      
Financing And Capitalization [Line Items]      
Unrestricted retained earnings $ 1,300,000,000 $ 1,300,000,000  
Consumers Energy Company | Commercial Paper      
Financing And Capitalization [Line Items]      
Short-term debt, authorized borrowings   500,000,000  
Short-term debt 30,000,000 $ 30,000,000  
Forward Contracts      
Financing And Capitalization [Line Items]      
Forward sales contracts aggregate price $ 250,000,000