Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Amortization of net actuarial loss, tax		$ 1		$ 3
Amortization of prior service credit, tax
Unrealized gain (loss) on investments, tax expense (tax benefit)		(1)		(1)
Consumers Energy Company [Member]
Amortization of net actuarial loss, tax				1
Unrealized gain (loss) on investments, tax expense (tax benefit)	(1)		2	(1)
Reclassification adjustments included in net income, tax				$ (3)