Notes Receivable (Schedule Of Current And Non-Current Notes Receivable) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	$ 198	$ 180
Total notes receivable	1,371	1,326
Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	17	29
Total notes receivable	17	45
EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Noncurrent notes receivable	1,171	1,088
Receivables, Net Of Allowance For Loan Losses [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	178	151
Receivables Held For Sale [Member] | EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	2	39
Michigan Tax Settlement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	20	29
Noncurrent notes receivable		19
Michigan Tax Settlement [Member] | Consumers Energy Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current notes receivable	$ 17	29
Noncurrent notes receivable		$ 16