Income Taxes (Principal Components Of Deferred Income Tax Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Employee benefits	$ (99)	$ 3
Gas inventory	(130)	(147)
Property, plant and equipment	(1,856)	(1,783)
Net regulatory tax liability	86	131
Reserves and accruals	57	71
Securitized costs	(190)	(73)
Tax loss and credit carryforwards	629	733
Other	15	(15)
Gross Deferred Tax Liabilities	(1,488)	(1,080)
Less: valuation allowance	(2)	(3)
Total net deferred income tax liabilities	(1,490)	(1,083)
Deferred tax assets, net of valuation reserves	785	935
Deferred tax liabilities	(2,275)	(2,018)
Consumers Energy Company [Member]
Employee benefits	(119)	(36)
Gas inventory	(130)	(147)
Property, plant and equipment	(1,911)	(1,848)
Net regulatory tax liability	86	131
Reserves and accruals	31	41
Securitized costs	(190)	(73)
Tax loss and credit carryforwards	48	61
Other	16	(13)
Gross Deferred Tax Liabilities	(2,169)	(1,884)
Less: valuation allowance	(1)	(1)
Total net deferred income tax liabilities	(2,170)	(1,885)
Deferred tax assets, net of valuation reserves	180	232
Deferred tax liabilities	$ (2,350)	$ (2,117)