Contingencies and Commitments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended								1 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Oct. 31, 2010	Dec. 31, 2004	Dec. 31, 2011 Consumers Energy Company [Member]	Dec. 31, 2010 Consumers Energy Company [Member]	Dec. 31, 2011 NREPA [Member] Consumers Energy Company [Member]	Dec. 31, 2011 Superfund Liability [Member] Consumers Energy Company [Member]	Jul. 31, 2011 Nuclear Fuel Disposal Cost [Member] Consumers Energy Company [Member]	Jun. 30, 2011 Nuclear Fuel Disposal Cost [Member] Consumers Energy Company [Member]	Jun. 30, 2011 Spent Nuclear Fuel Principal [Member] Consumers Energy Company [Member]	Jun. 30, 2011 Spent Nuclear Fuel Interest [Member] Consumers Energy Company [Member]	Dec. 31, 2011 Manufactured Gas Plant [Member] Consumers Energy Company [Member]	Dec. 31, 2011 Manufactured Gas Plant [Member] Consumers Energy Company [Member]	Dec. 31, 2011 MGP Sites [Member] Consumers Energy Company [Member]		Dec. 31, 2010 MGP Sites [Member] Consumers Energy Company [Member]
Demand For Payment By USEPA			$ 7
Cumulative Environmental Charge	224
Recorded liability	77
Accrual for Environmental Loss Contingencies							1	2					128
Spent Nuclear Fuel Obligation, Noncurrent										163	44	119
Discounted projected costs rate	4.34%												2.57%
Site Contingency Accrual Inflation Rate	1.00%												2.50%
Remaining undiscounted obligation amount	100												142
Undiscounted amount due within one year	21												14
Undiscounted amount due within two year	8												12
Undiscounted amount due within third year	4												12
Undiscounted amount due within fourth year	4												21
Undiscounted amount due within five year	5												13
Foreign Government Tax Claim On Sale				142
Remediation and other response activity costs, minimum							1	2
Remediation and other response activity costs. maximum							4	8
Litigation Settlement, Gross									120
Regulatory assets	2,466	2,093			2,466	2,093									156	[1]	58	[1]
Regulatory Liability, Noncurrent	1,875	1,988			1,875	1,988
Number of former MGPs					23
Increase in MGP Liability													104
Regulatory asset					2,467	2,112								156
Carrying Amounts					1
Maximum Obligation					$ 30

[1] These regulatory assets represent expenditures for which the MPSC has provided, or Consumers expects, recovery without a return on investment.