Notes Receivable (Schedule Of Current And Non-Current Notes Receivable) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current notes receivable	$ 41	$ 49
Total notes receivable	561	511
Consumers Energy Company [Member]
Current notes receivable		23
Total notes receivable	16	24
EnerBank [Member]
Current notes receivable	40	19
Noncurrent notes receivable	504	461
Other [Member]
Current notes receivable	1	30
Noncurrent notes receivable	16	1
Other [Member] | Consumers Energy Company [Member]
Current notes receivable		23
Noncurrent notes receivable	$ 16	$ 1