Regulatory Matters (Schedule of GCR Reconciliation Filing Pending with the MPSC) (Details) (USD $) In Millions	3 Months Ended		6 Months Ended		12 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 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]	Jun. 30, 2011 Consumers Energy Company [Member]	Jun. 30, 2010 Consumers Energy Company [Member]	Jun. 30, 2011 Consumers Energy Company [Member]	Jun. 30, 2010 Consumers Energy Company [Member]
Date Of Filing					June 2011	June 2010
Net Over-/(Under) Recovery of GCR Expense, Including Interest					$ 6	$ 1
Cost of gas sold	$ 220	$ 178	$ 988	$ 956	$ 1,200	$ 1,300	$ 197	$ 163	$ 950	$ 909