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Regulatory Matters (Schedule Of The Components Of Regulatory Assets and Liabilities) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, current $ 37 $ 20
Regulatory assets, noncurrent 1,743 1,764
Regulatory liabilities, current 155 80
Regulatory liability, noncurrent 3,681 3,715
Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, current 37 20
Regulatory assets, noncurrent 1,743 1,764
Total regulatory assets 1,780 1,784
Regulatory liabilities, current 155 80
Regulatory liability, noncurrent 3,681 3,715
Total regulatory liabilities $ 3,836 3,795
TCJA reserve for refund | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Current regulatory liability recovery end date 2019  
Regulatory liabilities, current $ 98 0
Regulatory liability, noncurrent $ 35 0
Reserve for customer refunds | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Current regulatory liability recovery end date 2019  
Regulatory liabilities, current $ 36 25
Income taxes, net | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Current regulatory liability recovery end date 2019  
Regulatory liabilities, current $ 18 52
Regulatory liability, noncurrent $ 1,537 1,564
Total regulatory liabilities   1,600
Other | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Current regulatory liability recovery end date 2019  
Regulatory liabilities, current $ 3 3
Regulatory liability, noncurrent 9 10
Cost of removal | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory liability, noncurrent $ 1,966 1,844
Renewable energy grant | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Noncurrent regulatory liability recovery end date 2043  
Regulatory liability, noncurrent $ 54 56
Renewable energy plan | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Noncurrent regulatory liability recovery end date 2028  
Regulatory liability, noncurrent $ 42 56
ARO | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory liability, noncurrent 38 50
Postretirement benefits | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory liability, noncurrent $ 0 135
Energy Waste Reduction Plan Incentive | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Current regulatory asset recovery end date 2019  
Regulatory assets, current $ 32 18
Regulatory assets, noncurrent $ 34 31
Regulatory Noncurrent Asset, End Date for Recovery Dec. 31, 2020  
Other | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Current regulatory asset recovery end date 2019  
Regulatory assets, current $ 5 2
Regulatory assets, noncurrent 2 2
Energy Waste Reduction Plan | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, noncurrent 26 39
Postretirement benefits | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, noncurrent 1,028 1,028
Securitized Costs | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, noncurrent $ 273 298
Regulatory Noncurrent Asset, End Date for Recovery Dec. 31, 2029  
ARO | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, noncurrent $ 175 161
Manufactured Gas Plant | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, noncurrent   142
Unamortized Loss On Reacquired Debt | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, noncurrent 68 53
Gas Storage Inventory Adjustments | Consumers Energy Company    
Public Utilities, General Disclosures [Line Items]    
Regulatory assets, noncurrent $ 4 $ 10