Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Benefits [Line Items]
Deferred income taxes and investment tax credits		$ 142,000,000	$ 157,000,000	$ 89,000,000
Interest accrued		0	0	0
Local Tax Authority
Income Tax Benefits [Line Items]
Valuation allowance - loss carryforward		1,000,000
2024 Renewable Energy Tax Credits
Income Tax Benefits [Line Items]
Deferred income taxes and investment tax credits		59,000,000
Consumers Energy Company
Income Tax Benefits [Line Items]
Deferred income taxes and investment tax credits		115,000,000	156,000,000	134,000,000
Interest accrued		0	$ 0	$ 0
Consumers Energy Company | 2023 Renewable Energy Tax Credits
Income Tax Benefits [Line Items]
Deferred income taxes and investment tax credits		37,000,000
Consumers Energy Company | 2024 Renewable Energy Tax Credits
Income Tax Benefits [Line Items]
Deferred income taxes and investment tax credits		$ 39,000,000
Consumers Energy Company | 2024 Renewable Energy Tax Credits | Forecast
Income Tax Benefits [Line Items]
Deferred income taxes and investment tax credits	$ 13,000,000