Notes Receivable (Schedule Of Current And Non-Current Notes Receivable) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	$ 197	$ 180
EnerBank notes receivable held for sale	31	39
Total notes receivable	1,382	1,326
Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	30	29
Total notes receivable	46	45
EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Noncurrent notes receivable	1,134	1,088
Receivables, Net Of Allowance For Loan Losses [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	167	151
Receivables Held For Sale [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
EnerBank notes receivable held for sale	31	39
Michigan Tax Settlement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	30	29
Noncurrent notes receivable	20	19
Michigan Tax Settlement [Member] | Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	30	29
Noncurrent notes receivable	$ 16	$ 16