v3.25.4
Retirement Benefits (Narrative) (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2025
USD ($)
yr
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Defined Benefit Plan Disclosure [Line Items]      
Ultimate health care cost trend rate 4.75%    
Year health care cost trend rate reaches ultimate trend rate 2034    
Union employees percentage 44.00%    
Under Age 65      
Defined Benefit Plan Disclosure [Line Items]      
Health care cost trend rate assumed next fiscal year 8.00% 8.50%  
Over Age 65      
Defined Benefit Plan Disclosure [Line Items]      
Health care cost trend rate assumed next fiscal year 9.75% 10.25%  
OPEB Plan      
Defined Benefit Plan Disclosure [Line Items]      
Retirement age requirement | yr 55    
Retirement years of service 10 years    
Retirement years of service with disability 15 years    
Estimated time of amortization of gains losses 9 years 9 years 9 years
Estimated time of prior service cost 7 years    
OPEB Plan | Volatility Mechanism      
Defined Benefit Plan Disclosure [Line Items]      
Deferred credits (costs) $ 6 $ 11  
OPEB Plan | Volatility Mechanism      
Defined Benefit Plan Disclosure [Line Items]      
Deferred credits (costs)     $ 23
DB Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Amortized net gains and losses in excess of PBO or MRV 10.00%    
Period for gains or losses to be included in market related value 5 years    
Accumulated benefit obligation $ 1,900 1,900  
DB Pension Plans | Fixed-income securities      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 40.00%    
DB Pension Plans | Equity securities      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 38.00%    
DB Pension Plans | Real asset investments      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 11.00%    
DB Pension Plans | Return-seeking fixed income      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 7.00%    
DB Pension Plans | Liquid alternative investments      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 4.00%    
DB Pension Plans | Volatility Mechanism      
Defined Benefit Plan Disclosure [Line Items]      
Deferred credits (costs)   $ 15 11
DB Pension Plans | Volatility Mechanism      
Defined Benefit Plan Disclosure [Line Items]      
Deferred credits (costs) $ (3)    
Postretirement Health Trusts | Fixed-income securities      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 40.00%    
Postretirement Health Trusts | Equity securities      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 38.00%    
Postretirement Health Trusts | Real asset investments      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 11.00%    
Postretirement Health Trusts | Return-seeking fixed income      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 7.00%    
Postretirement Health Trusts | Liquid alternative investments      
Defined Benefit Plan Disclosure [Line Items]      
Target allocation percentage 4.00%    
Consumers Energy Company      
Defined Benefit Plan Disclosure [Line Items]      
Ultimate health care cost trend rate 4.75%    
Year health care cost trend rate reaches ultimate trend rate 2034    
Union employees percentage 45.00%    
Consumers Energy Company | Under Age 65      
Defined Benefit Plan Disclosure [Line Items]      
Health care cost trend rate assumed next fiscal year 8.00% 8.50%  
Consumers Energy Company | Over Age 65      
Defined Benefit Plan Disclosure [Line Items]      
Health care cost trend rate assumed next fiscal year 9.75% 10.25%  
Consumers Energy Company | OPEB Plan      
Defined Benefit Plan Disclosure [Line Items]      
Retirement age requirement | yr 55    
Retirement years of service 10 years    
Retirement years of service with disability 15 years    
Estimated time of prior service cost 7 years    
Defined Company Contribution Plan      
Defined Benefit Plan Disclosure [Line Items]      
Plan cost, defined contribution plan $ 57 $ 53 51
Defined Company Contribution Plan | Consumers Energy Company      
Defined Benefit Plan Disclosure [Line Items]      
Plan cost, defined contribution plan 55 52 50
DC SERP      
Defined Benefit Plan Disclosure [Line Items]      
Plan cost, defined contribution plan $ 1 1 1
Minimum years of participation before vesting 5 years    
Trust assets $ 18 17  
401 (K) Plan      
Defined Benefit Plan Disclosure [Line Items]      
Plan cost, defined contribution plan 46 41 41
401 (K) Plan | Consumers Energy Company      
Defined Benefit Plan Disclosure [Line Items]      
Plan cost, defined contribution plan $ 44 $ 39 $ 40
Pension Plan A | DB Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Estimated time of amortization of gains losses 7 years 8 years 8 years
Pension Plan B | DB Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Estimated time of amortization of gains (losses) life expectancy 17 years 17 years 17 years
Minimum | Defined Company Contribution Plan      
Defined Benefit Plan Disclosure [Line Items]      
Contribution range 5.00%    
Minimum | DC SERP      
Defined Benefit Plan Disclosure [Line Items]      
Plan contribution percentage 5.00%    
Minimum | 401 (K) Plan      
Defined Benefit Plan Disclosure [Line Items]      
Contribution range 4.00%    
Maximum | Defined Company Contribution Plan      
Defined Benefit Plan Disclosure [Line Items]      
Contribution range 10.00%    
Maximum | DC SERP      
Defined Benefit Plan Disclosure [Line Items]      
Plan contribution percentage 15.00%    
Maximum | 401 (K) Plan      
Defined Benefit Plan Disclosure [Line Items]      
Contribution range 6.00%