Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Amortization of net actuarial loss, tax		$ 1		$ 2
Amortization of prior service credit, tax
Unrealized gain (loss) on investments, tax expense (tax benefit)
Consumers Energy Company [Member]
Amortization of net actuarial loss, tax		1		1
Unrealized gain (loss) on investments, tax expense (tax benefit)	1	(1)	3	(1)
Reclassification adjustments included in net income, tax				$ (3)