Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net loss arising during the period TAX	$ (1)	$ (4)	$ (5)
Prior service credit adjustment TAX	0	3	0
Amortization of net actuarial loss TAX	1	1	0
Amortization of prior service credit TAX	(1)	0	0
Unrealized gain on investments TAX	0	0	0
Other-than-temporary impairment included in net income TAX	0	0	2
Unrealized loss on derivative instruments, TAX	0	0	0
Consumers Energy Company
Net loss arising during the period TAX	2	(1)	(1)
Amortization of net actuarial loss TAX	0	0	0
Unrealized gain on investments TAX	0	1	2
Reclassification adjustments included in net income TAX	0	(6)	0
Other-than-temporary impairment included in net income TAX	$ 0	$ 0	$ 2