Income Taxes (Summary of Principal Components of Deferred Income Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Deferred income tax assets
Tax loss and credit carryforwards	$ 258	$ 428
Net regulatory tax liability	307	305
Reserves and accruals	27	28
Total deferred income tax assets	592	761
Valuation allowance	(1)	(2)
Total deferred income tax assets, net of valuation allowance	591	759
Deferred income tax liabilities
Plant, property, and equipment	(2,682)	(2,520)
Employee benefits	(507)	(473)
Gas inventory	(38)	(66)
Securitized costs	(167)	(194)
Other	(122)	(121)
Total deferred income tax liabilities	(3,516)	(3,374)
Total net deferred income tax liabilities	(2,925)	(2,615)
Consumers Energy Company
Deferred income tax assets
Tax loss and credit carryforwards	37	175
Net regulatory tax liability	307	305
Reserves and accruals	24	27
Total deferred income tax assets, net of valuation allowance	368	507
Deferred income tax liabilities
Plant, property, and equipment	(2,658)	(2,498)
Employee benefits	(489)	(459)
Gas inventory	(38)	(66)
Securitized costs	(167)	(194)
Other	(69)	(79)
Total deferred income tax liabilities	(3,421)	(3,296)
Total net deferred income tax liabilities	$ (3,053)	$ (2,789)