Income Taxes (Principal Components Of Deferred Income Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred income tax assets
Tax loss and credit carryforwards	$ 332	$ 483
Net regulatory tax liability	349	372
Reserves and accruals	32	62
Total deferred income tax assets	713	917
Valuation allowance	(2)	(1)
Total deferred income tax assets, net of valuation allowance	711	916
Deferred income tax liabilities
Plant, property, and equipment	(2,395)	(2,287)
Employee benefits	(399)	(364)
Securitized costs	(46)	(53)
Gas inventory	(22)	(24)
Other	(59)	(51)
Total deferred income tax liabilities	(2,921)	(2,779)
Total net deferred income tax liabilities	(2,210)	(1,863)
Consumers Energy Company
Deferred income tax assets
Tax loss and credit carryforwards	134	216
Net regulatory tax liability	349	372
Reserves and accruals	24	24
Total deferred income tax assets, net of valuation allowance	507	612
Deferred income tax liabilities
Plant, property, and equipment	(2,341)	(2,230)
Employee benefits	(388)	(365)
Securitized costs	(46)	(53)
Gas inventory	(22)	(24)
Other	(50)	(34)
Total deferred income tax liabilities	(2,847)	(2,706)
Total net deferred income tax liabilities	$ (2,340)	$ (2,094)