Notes Receivable (Schedule Of Current And Non-Current Notes Receivable) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	$ 180	$ 128
EnerBank notes receivable held for sale	39	16
Total notes receivable	1,326	1,161
Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	29
Total notes receivable	45
EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	219	144
Noncurrent notes receivable	1,088	1,017
Receivables, Net Of Allowance For Loan Losses [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	151	128
Receivables Held For Sale [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	39	$ 16
State Of Michigan Tax Settlement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	29
Noncurrent notes receivable	19
State Of Michigan Tax Settlement [Member] | Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	29
Noncurrent notes receivable	$ 16