v3.25.4
Retirement Benefits (Schedule of Retirement Benefit Plan Assets (Liabilities)) (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]    
Non-current assets $ 1,957 $ 1,627
Non-current liabilities 95 96
Consumers Energy Company    
Defined Benefit Plan Disclosure [Line Items]    
Non-current assets 1,821 1,514
Non-current liabilities 70 70
DB Pension Plans    
Defined Benefit Plan Disclosure [Line Items]    
Non-current assets 1,054 870
DB Pension Plans | Consumers Energy Company    
Defined Benefit Plan Disclosure [Line Items]    
Non-current assets 1,009 836
OPEB Plan    
Defined Benefit Plan Disclosure [Line Items]    
Non-current assets 903 757
OPEB Plan | Consumers Energy Company    
Defined Benefit Plan Disclosure [Line Items]    
Non-current assets 812 678
DB SERP    
Defined Benefit Plan Disclosure [Line Items]    
Current liabilities 10 10
Non-current liabilities 94 95
DB SERP | Consumers Energy Company    
Defined Benefit Plan Disclosure [Line Items]    
Current liabilities 7 7
Non-current liabilities $ 69 $ 69