Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Level 3 Inputs) (Details) (Fair Value, Inputs, Level 3 [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance at beginning of period			$ 4	$ 2
Total gains (losses) included in earnings		(1)
Total gains (losses) offset through regulatory accounting	1	9	(18)	7
Purchases			(1)	(1)
Settlements			16
Balance at end of period	1	8	1	8
Unrealized gains (losses) included in earnings relating to assets and liabilities still held at end of period		(1)		(1)
Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance at beginning of period			4	2
Total gains (losses) offset through regulatory accounting	1	9	(18)	7
Purchases			(1)	1
Settlements		1	16
Balance at end of period	$ 1	$ 10	$ 1	$ 10