Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net gain (loss) arising during the period, tax	$ (5)		$ (18)
Amortization of net actuarial loss, tax		$ 4	1
Amortization of prior service credit, tax
Unrealized gain (loss) on investments, tax expense (tax benefit)		(1)	(1)
Other-than-temporary impairment, tax	2
Reclassification adjustments included in net income (loss), tax
Consumers Energy Company [Member]
Net gain (loss) arising during the period, tax	(1)	2	(7)
Amortization of net actuarial loss, tax		2	1
Unrealized gain (loss) on investments, tax expense (tax benefit)	2	(1)	$ 2
Reclassification adjustments included in net income, tax		$ (3)
Other-than-temporary impairment, tax	$ 2