Income Taxes (Summary of Principal Components of Deferred Income Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred income tax assets
Tax loss and credit carryforwards	$ 428	$ 385
Net regulatory tax liability	305	318
Reserves and accruals	28	35
Total deferred income tax assets	761	738
Valuation allowance	(2)	(2)
Total deferred income tax assets, net of valuation allowance	759	736
Deferred income tax liabilities
Plant, property, and equipment	(2,520)	(2,515)
Employee benefits	(473)	(433)
Gas inventory	(66)	(53)
Securitized costs	(194)	(39)
Other	(121)	(103)
Total deferred income tax liabilities	(3,374)	(3,143)
Total net deferred income tax liabilities	(2,615)	(2,407)
Consumers Energy Company
Deferred income tax assets
Tax loss and credit carryforwards	175	145
Net regulatory tax liability	305	318
Reserves and accruals	27	28
Total deferred income tax assets, net of valuation allowance	507	491
Deferred income tax liabilities
Plant, property, and equipment	(2,498)	(2,458)
Employee benefits	(459)	(423)
Gas inventory	(66)	(53)
Securitized costs	(194)	(39)
Other	(79)	(103)
Total deferred income tax liabilities	(3,296)	(3,076)
Total net deferred income tax liabilities	$ (2,789)	$ (2,585)