v3.26.1
Financings and Capitalization (Schedule of Major Long-Term Debt Issuances and Retirements) (Details) - USD ($)
$ in Millions
6 Months Ended
Dec. 31, 2026
Jun. 30, 2026
Jun. 30, 2025
Debt Instrument [Line Items]      
Principal Amount   $ 1,216  
Payment for purchase of first mortgage bonds   883 $ 841
Repayments of debt   685  
Consumers Energy Company      
Debt Instrument [Line Items]      
Principal Amount   $ 850  
Debt instrument, interest rate, stated (in percent)   5.24%  
Payment for purchase of first mortgage bonds   $ 175 $ 57
Repayments of debt   115  
First mortgage bonds | First mortgage bonds | Consumers Energy Company      
Debt Instrument [Line Items]      
Principal Amount   $ 850  
Debt instrument, interest rate, stated (in percent)   5.125%  
NorthStar Clean Energy, Including Subsidiaries      
Debt Instrument [Line Items]      
Debt instrument, increase (decrease), net   $ 366  
Repayments of debt   270  
NorthStar Clean Energy, Including Subsidiaries | Construction financing agreement      
Debt Instrument [Line Items]      
Payment for purchase of first mortgage bonds   156  
Repayments of debt   270  
NorthStar Clean Energy, Including Subsidiaries | Term Loan      
Debt Instrument [Line Items]      
Debt instrument, increase (decrease), net   24  
NorthStar Clean Energy, Including Subsidiaries | Term Loan      
Debt Instrument [Line Items]      
Debt instrument, increase (decrease), net   90  
NorthStar Clean Energy, Including Subsidiaries | Construction Financing Agreement, Second Half Of 2026 | Construction financing agreement      
Debt Instrument [Line Items]      
Debt instrument, increase (decrease), net   252  
NorthStar Clean Energy, Including Subsidiaries | Construction Financing Agreement, Second Half Of 2026 | Construction financing agreement | Forecast      
Debt Instrument [Line Items]      
Debt conversion, converted instrument, amount $ 133    
Debt instrument, term (in years) 5 years    
Payment for purchase of first mortgage bonds $ 119    
NorthStar Clean Energy, Including Subsidiaries | Construction Financing Agreement, First Half Of 2026 | Construction financing agreement      
Debt Instrument [Line Items]      
Debt conversion, converted instrument, amount   114  
CMS Energy      
Debt Instrument [Line Items]      
Repayments of debt   $ 300  
CMS Energy | Senior notes | Senior notes      
Debt Instrument [Line Items]      
Debt instrument, interest rate, stated (in percent)   3.00%  
Repayments of debt   $ 300