Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Amortization of net actuarial loss, tax	$ 1	$ 1	$ 2	$ 1
Unrealized gain (loss) on investments, tax expense (tax benefit)
Reclassification adjustments included in net income (loss), tax
Consumers Energy Company [Member]
Amortization of net actuarial loss, tax	$ 1		$ 1
Unrealized gain (loss) on investments, tax expense (tax benefit)	$ (1)	$ 1	(1)	$ 2
Reclassification adjustments included in net income, tax			$ (3)