Contingencies And Commitments (Contingencies And Commitments) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended								1 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Oct. 31, 2010	Sep. 30, 2012 Consumers Energy Company [Member]	Dec. 31, 2011 Consumers Energy Company [Member]	Sep. 30, 2012 NREPA [Member] Consumers Energy Company [Member]	Sep. 30, 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]	Sep. 30, 2012 Manufactured Gas Plant [Member] Consumers Energy Company [Member] item
Demand for payment by USEPA				$ 7
Cumulative environmental charge	226
Recorded liability	64												125
Accrual for environmental loss contingencies							4	2
Discounted projected costs rate	4.34%												2.57%
Site contingency accrual inflation rate	1.00%												2.50%
Remaining undiscounted obligation amount	85												137
Undiscounted amount due within one year	4												7
Undiscounted amount due within two year	10												11
Undiscounted amount due within third year	5												11
Undiscounted amount due within fourth year	4												20
Undiscounted amount due within five year	4												11
Foreign government tax claim on sale	142
After tax income in discontinued operations recognized after expiration of tax indemnification	7	2
Remediation and other response activity costs, minimum							4	2
Remediation and other response activity costs. maximum							7	8
Litigation settlement, gross									120
Spent nuclear fuel obligation, noncurrent										163	44	119
Number of former MGPs													23
Regulatory assets, noncurrent	$ 2,273		$ 2,466		$ 2,273	$ 2,466							$ 153