Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Income	$ 659	$ 462	$ 553
Retirement Benefits Liability
Net loss arising during the period, net of tax	(4)	(5)	(8)
Prior service credit adjustment, net of tax	(1)	4	0
Amortization of net actuarial loss	4	2	2
Amortization of prior service credit, net of tax	(1)	(1)	(1)
Investments
Unrealized gain on investments	0	0	1
Other-than-temporary impairment included in net income, net of tax	0	0	3
Derivatives
Unrealized loss on derivative instruments, net of tax of $- for all periods	(2)	0	0
Other Comprehensive Loss	(2)	0	(3)
Comprehensive Income	657	462	550
Comprehensive Income Attributable to Noncontrolling Interests	2	2	2
Comprehensive Income Attributable to CMS Energy	655	460	548
Consumers Energy Company
Net Income	705	632	616
Retirement Benefits Liability
Net loss arising during the period, net of tax	6	(4)	(3)
Amortization of net actuarial loss	2	1	1
Investments
Unrealized gain on investments	(1)	3	3
Reclassification adjustments included in net income	1	(9)	0
Other-than-temporary impairment included in net income, net of tax	0	0	2
Derivatives
Other Comprehensive Loss	8	(9)	3
Comprehensive Income Attributable to CMS Energy	$ 713	$ 623	$ 619