Income Taxes (Principal Components Of Deferred Income Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets
Tax loss and credit carryforwards	$ 239	$ 385
Net regulatory tax liability	385	395
Reserves and accruals	43	39
Total deferred income tax assets	667	819
Valuation allowance	(2)	(8)
Total deferred income tax assets, net of valuation allowance	665	811
Deferred income tax liabilities
Plant, property, and equipment	(2,033)	(1,955)
Employee benefits	(172)	(165)
Securitized costs	(59)	(65)
Gas inventory	(32)	(35)
Other	(24)	(78)
Total deferred income tax liabilities	(2,320)	(2,298)
Total net deferred income tax liabilities	(1,655)	(1,487)
Consumers Energy Company
Deferred income tax assets
Tax loss and credit carryforwards	20	64
Net regulatory tax liability	385	395
Reserves and accruals	24	21
Total deferred income tax assets, net of valuation allowance	429	480
Deferred income tax liabilities
Plant, property, and equipment	(1,995)	(1,943)
Employee benefits	(178)	(172)
Securitized costs	(59)	(65)
Gas inventory	(32)	(35)
Other	(29)	(74)
Total deferred income tax liabilities	(2,293)	(2,289)
Total net deferred income tax liabilities	$ (1,864)	$ (1,809)