Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net income	$ 525	$ 479	$ 454
Retirement Benefits Liability
Net gain (loss) arising during the period, net of tax	1	(29)	26
Prior service credit adjustment, net of tax			5
Amortization of net actuarial loss (gain), net of tax	5	3	4
Amortization of prior service credit, net of tax	(1)	(1)
Investments
Unrealized gain (loss) on investments, net of tax	(3)	(1)	(2)
Derivative Instruments
Reclassification adjustments included in net income, net of tax		1
Other Comprehensive Income (Loss)	2	(27)	33
Comprehensive Income	527	452	487
Comprehensive Income Attributable to Noncontrolling Interest	2	2	2
Comprehensive Income Attributable to CMS Energy	525	450	485
Consumers Energy Company [Member]
Net income	594	567	534
Retirement Benefits Liability
Net gain (loss) arising during the period, net of tax	3	(11)	5
Amortization of net actuarial loss (gain), net of tax	4	2	3
Investments
Unrealized gain (loss) on investments, net of tax	(1)	4	1
Reclassification adjustments included in net income, net of tax	(5)		(3)
Derivative Instruments
Other Comprehensive Income (Loss)	1	(5)	6
Comprehensive Income Attributable to CMS Energy	$ 595	$ 562	$ 540