Regulatory Matters (Schedule of GCR Reconciliation Filing Pending with the MPSC) (Details) (USD $) In Millions	3 Months Ended		9 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Mar. 31, 2011 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member]	Mar. 31, 2010 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member]	Sep. 30, 2011 Consumers Energy Company [Member]	Sep. 30, 2010 Consumers Energy Company [Member]	Sep. 30, 2011 Consumers Energy Company [Member]	Sep. 30, 2010 Consumers Energy Company [Member]
Date Of Filing					June 2011	June 2010
Net Over/(Under) Recovery, Including Interest, Requested by Consumers					$ 6	$ 1
Cost of gas sold	$ 107	$ 104	$ 1,095	$ 1,060	$ 1,200	$ 1,300	$ 88	$ 92	$ 1,038	$ 1,001