Contingencies and Commitments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended									1 Months Ended					3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Oct. 31, 2010	Dec. 31, 2004	Mar. 31, 2012 Consumers Energy Company [Member]	Dec. 31, 2011 Consumers Energy Company [Member]	Mar. 31, 2012 NREPA [Member] Consumers Energy Company [Member]	Mar. 31, 2012 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]	Mar. 31, 2012 Manufactured Gas Plant [Member] Consumers Energy Company [Member]	Mar. 31, 2012 Indemnification Expiration [Member]
Demand For Payment By USEPA				$ 7
Cumulative Environmental Charge	225
Recorded liability	71
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	95													141
Undiscounted amount due within one year	16													11
Undiscounted amount due within two year	8													11
Undiscounted amount due within third year	4													11
Undiscounted amount due within fourth year	4													20
Undiscounted amount due within five year	5													11
Foreign Government Tax Claim On Sale					142
After Tax Income in Discontinued Operations Recognized After Expiration of Tax Indemnification	7	2													7
Remediation and other response activity costs, minimum								1	2
Remediation and other response activity costs. maximum								4	8
Litigation Settlement, Gross										120
Regulatory assets, noncurrent	2,362		2,466			2,362	2,466							155
Regulatory Liability, Noncurrent	1,919		1,875			1,919	1,875
Number of former MGPs						23
Carrying Amounts						1
Maximum Obligation						$ 30