Notes Receivable (Schedule Of Current And Non-Current Notes Receivable) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	$ 84	$ 41
Total notes receivable	623	561
Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	25
Total notes receivable	25	16
EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	58	40
Noncurrent notes receivable	539	504
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	26	1
Noncurrent notes receivable		16
Other [Member] | Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	25
Noncurrent notes receivable		$ 16