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Revenue (Narrative) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Disaggregation of Revenue [Line Items]      
Bad debt expense $ 34 $ 50 $ 22
Unbilled receivables 494 663  
Consumers Energy Company      
Disaggregation of Revenue [Line Items]      
Bad debt expense 34 50 22
Regulatory liability 3,950 3,900  
Unbilled receivables 494 663  
Consumers Energy Company | Contributions to assistance programs      
Disaggregation of Revenue [Line Items]      
Regulatory liability 10    
Consumers Energy Company | Voluntary refund mechanism      
Disaggregation of Revenue [Line Items]      
Regulatory liability   22  
Consumers Energy Company | Reserve for customer refunds      
Disaggregation of Revenue [Line Items]      
Regulatory liability 15    
Accounts Receivable      
Disaggregation of Revenue [Line Items]      
Bad debt expense 34 50 22
Accounts Receivable | Consumers Energy Company      
Disaggregation of Revenue [Line Items]      
Bad debt expense $ 34 $ 50 $ 22