Contingencies and Commitments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended										1 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Oct. 31, 2010	Dec. 31, 2004	Jun. 30, 2011 Consumers Energy Company [Member] Manufactured Gas Plant [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Manufactured Gas Plant [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Deferred MGP Expenditures [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Big Rock [Member]	Jun. 30, 2011 Consumers Energy Company [Member] NREPA [Member]	Jun. 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]	Jun. 30, 2011 Consumers Energy Company [Member]	Dec. 31, 2010 Consumers Energy Company [Member]
Demand For Payment By USEPA			$ 7
Cumulative Environmental Charge	223
Recorded liability	88
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	109
Undiscounted amount due within one year	16
Undiscounted amount due within two year	16
Undiscounted amount due within third year	7
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						43				8
Litigation Settlement, Gross											120
Regulatory assets	2,050	2,093					27	85							2,050	2,093
Regulatory Liability, Noncurrent	1,860	1,988													1,860	1,988
Number of former MGPs															23
Regulatory asset					55
MGP Average Five Year Expenditures						$ 6