Income Taxes (Principal Components Of Deferred Income Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets
Tax loss and credit carryforwards	$ 385	$ 453
Net regulatory tax liability	395	411
Reserves and accruals	39	40
Total deferred income tax assets	819	904
Valuation allowance	(8)	(15)
Total deferred income tax assets, net of valuation allowance	811	889
Deferred income tax liabilities
Plant, property, and equipment	(1,955)	(1,891)
Employee benefits	(165)	(96)
Securitized costs	(65)	(71)
Gas inventory	(35)	(37)
Other	(78)	(63)
Total deferred income tax liabilities	(2,298)	(2,158)
Total net deferred income tax liabilities	(1,487)	(1,269)
Consumers Energy Company
Deferred income tax assets
Tax loss and credit carryforwards	64	101
Net regulatory tax liability	395	411
Reserves and accruals	21	21
Total deferred income tax assets, net of valuation allowance	480	533
Deferred income tax liabilities
Plant, property, and equipment	(1,943)	(1,901)
Employee benefits	(172)	(105)
Securitized costs	(65)	(71)
Gas inventory	(35)	(37)
Other	(74)	(59)
Total deferred income tax liabilities	(2,289)	(2,173)
Total net deferred income tax liabilities	$ (1,809)	$ (1,640)