Contingencies and Commitments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended				9 Months Ended							1 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Oct. 31, 2010	Dec. 31, 2004	Sep. 30, 2011 Consumers Energy Company [Member] Michigan Single Business Tax [Member]	Sep. 30, 2011 Michigan Single Business Tax [Member]	Sep. 30, 2011 Consumers Energy Company [Member] Manufactured Gas Plant [Member]	Sep. 30, 2011 Consumers Energy Company [Member] Manufactured Gas Plant [Member]	Sep. 30, 2011 Consumers Energy Company [Member] Deferred MGP Expenditures [Member]	Sep. 30, 2011 Consumers Energy Company [Member] NREPA [Member]	Sep. 30, 2011 Consumers Energy Company [Member] Superfund Liability [Member]	Jul. 31, 2011 Consumers Energy Company [Member] Nuclear Fuel Disposal Cost [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Nuclear Fuel Disposal Cost [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Spent Nuclear Fuel Principal [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Spent Nuclear Fuel Interest [Member]	Sep. 30, 2011 Consumers Energy Company [Member]	Dec. 31, 2010 Consumers Energy Company [Member]
Demand For Payment By USEPA			$ 7
Cumulative Environmental Charge	224
Recorded liability	82
Accrual for Environmental Loss Contingencies								28		2	2
Spent Nuclear Fuel Obligation, Noncurrent													163	44	119
Discounted projected costs rate	4.34%
Site Contingency Accrual Inflation Rate	1.00%
Remaining undiscounted obligation amount	103
Undiscounted amount due within one year	8
Undiscounted amount due within two year	18
Undiscounted amount due within third year	8
Undiscounted amount due within fourth year	5
Undiscounted amount due within five year	4
Foreign Government Tax Claim On Sale				142
Remediation and other response activity costs, minimum								28			2
Remediation and other response activity costs. maximum								42			8
Litigation Settlement, Gross												120
Regulatory assets	2,002	2,093							26							2,002	2,093
Regulatory Liability, Noncurrent	1,874	1,988														1,874	1,988
Number of former MGPs																23
Regulatory asset							54
MGP Average Five Year Expenditures								5
Carrying Amounts																1
Maximum Obligation																30
Change in Non Income Related Tax Accrual					$ 10	$ 17