Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Income	$ 682	$ 659	$ 462
Retirement Benefits Liability
Net loss arising during the period, net of tax	(7)	(4)	(5)
Prior service credit adjustment, net of tax	0	(1)	4
Amortization of net actuarial loss	3	4	2
Amortization of prior service credit, net of tax	(2)	(1)	(1)
Derivatives
Unrealized loss on derivative instruments, net of tax of $(1), $-, and $-	(3)	(2)
Unrealized loss on derivative instruments, net of tax of $(1), $-, and $-			0
Reclassification adjustments included in net income, net of tax of $- for all periods	1	0
Reclassification adjustments included in net income, net of tax of $- for all periods			0
Other Comprehensive Loss	(8)	(4)	0
Comprehensive Income	674	655	462
Comprehensive Income Attributable to Noncontrolling Interests	2	2	2
Comprehensive Income Attributable to CMS Energy	672	653	460
Consumers Energy Company
Net Income	743	705	632
Retirement Benefits Liability
Net loss arising during the period, net of tax	(8)	6	(4)
Amortization of net actuarial loss	1	2	1
Investments
Unrealized gain on investments	0	(1)	3
Reclassification adjustments included in net income	0	1	(9)
Derivatives
Other Comprehensive Loss	(7)	8	(9)
Comprehensive Income	$ 736	$ 713	$ 623