Retirement Benefits (Schedule Of Net Benefit Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension And DB SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 54	$ 49	$ 49
Interest expense	100	105	106
Expected return on plan assets	(127)	(125)	(112)
Amortization of Net loss	101	79	65
Amortization of Prior service cost (credit)	3	5	5
Net periodic cost (credit)	131	113	113
Pension And DB SERP [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	52	48	48
Interest expense	96	100	101
Expected return on plan assets	(124)	(122)	(109)
Amortization of Net loss	98	77	63
Amortization of Prior service cost (credit)	3	5	5
Net periodic cost (credit)	125	108	108
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	29	32	27
Interest expense	65	82	77
Expected return on plan assets	(77)	(66)	(66)
Amortization of Net loss	26	46	30
Amortization of Prior service cost (credit)	(31)	(20)	(20)
Net periodic cost (credit)	12	74	48
OPEB [Member] | Consumers Energy Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	28	31	26
Interest expense	63	79	74
Expected return on plan assets	(72)	(61)	(61)
Amortization of Net loss	27	47	31
Amortization of Prior service cost (credit)	(30)	(20)	(20)
Net periodic cost (credit)	$ 16	$ 76	$ 50