Regulatory Matters (Schedule Of The Components Of PSCR And GCR Over/(Under) Recoveries) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Public Utilities, General Disclosures [Line Items]
Accrued rate refunds	$ 33	$ 21
Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Accrued rate refunds	33	21
Consumers Energy Company [Member] | Power Supply Cost Recover (PSCR) [Member]
Public Utilities, General Disclosures [Line Items]
Accrued rate refunds	27	8
Consumers Energy Company [Member] | Gas Cost Recover (GCR) [Member]
Public Utilities, General Disclosures [Line Items]
Accrued rate refunds	$ 6	$ 13