Retirement Benefits (Schedule Of Major Components Of Actuarial Losses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	$ 458	$ (308)
Pension Plan [Member] | Discount Rate Changes [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	235
Pension Plan [Member] | RP-2014 Mortality Table [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	150
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	230	(440)
OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	223	(424)
OPEB [Member] | Discount Rate Changes [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	155
OPEB [Member] | Discount Rate Changes [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	150
OPEB [Member] | RP-2014 Mortality Table [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	145
OPEB [Member] | RP-2014 Mortality Table [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	$ 141