Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Income	$ 172	$ 186	$ 464	$ 475
Retirement Benefits Liability
Amortization of net actuarial loss, net of tax		1	1	2
Amortization of prior service credit, net of tax				(1)
Investments
Unrealized gain (loss) on investments, net of tax	1	1	2	1
Other Comprehensive Income (Loss)	1	2	3	2
Comprehensive Income	173	188	467	477
Comprehensive Income Attributable to Noncontrolling Interest			1	1
Comprehensive Income Attributable to CMS Energy	173	188	466	476
Consumers Energy Company [Member]
Net Income	181	195	496	499
Retirement Benefits Liability
Amortization of net actuarial loss, net of tax			1
Investments
Unrealized gain (loss) on investments, net of tax		(2)	2	3
Reclassification adjustments included in net income, net of tax			(8)
Other Comprehensive Income (Loss)		(2)	(5)	3
Comprehensive Income Attributable to CMS Energy	$ 181	$ 193	$ 491	$ 502