Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Amortization of net actuarial loss, tax	$ 1		$ 3	$ 1
Amortization of prior service credit, tax
Unrealized gain (loss) on investments, tax expense (tax benefit)	$ 1		$ 1
Reclassification adjustments included in net income (loss), tax
Consumers Energy Company [Member]
Amortization of net actuarial loss, tax			$ 1
Unrealized gain (loss) on investments, tax expense (tax benefit)		$ (1)	(1)	$ 1
Reclassification adjustments included in net income, tax			$ (3)