Consolidated Statements Of Changes In Equity - USD ($) $ in Millions	Consumers Energy Company [Member] CMS Energy Common Stock [Member]	Consumers Energy Company [Member] Other Paid-in Capital [Member]	Consumers Energy Company [Member] Accumulated Other Comprehensive Loss [Member]	Consumers Energy Company [Member] Retirement Benefits Liability [Member]	Consumers Energy Company [Member] Investments [Member]	Consumers Energy Company [Member] Retained Earnings (Accumulated Deficit) [Member]	Consumers Energy Company [Member] Preferred Stock [Member]	Consumers Energy Company [Member]	CMS Energy Common Stock [Member]	Other Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retirement Benefits Liability [Member]	Investments [Member]	Retained Earnings (Accumulated Deficit) [Member]	Noncontrolling Interest [Member]	Total
Total Equity, beginning at Dec. 31, 2014	$ 841	$ 3,574	$ (7)	$ (26)	$ 19	$ 832	$ 37	$ 5,277	$ 3	$ 4,774	$ (49)	$ (48)	$ (1)	$ (1,058)	$ 37	$ 3,707
Beginning of period, shares at Dec. 31, 2014									275,184,000
Common stock issued										65
Number of Shares Issued									2,062,000
Common stock repurchased										(12)
Common stock repurchased, shares									(306,000)
Common stock reissued										10
Common stock reissued, shares									288,000
Common stock reacquired, value
Common stock reacquired, shares									(65,000)
Stockholder contribution		150
Net gain (loss) arising during the period				3				3				1				1
Amortization of net actuarial loss				4				4				5				5
Amortization of prior service credit												(1)				(1)
Unrealized gain (loss) on investments					(1)			(1)					(3)			(3)
Reclassification adjustments included in net income, net of tax					(5)			(5)
Net income (loss) attributable to CMS Energy														523		523
Net Income						594		594								525
Dividends declared on common stock						(474)								(320)
Dividends declared on preferred stock						(2)
Income Attributable to Noncontrolling Interests															2	2
Distributions, and other changes in noncontrolling interests															(2)
End of period, shares at Dec. 31, 2015									277,163,000
Total Equity, end at Dec. 31, 2015	841	3,724	(6)	(19)	13	950	37	5,546	$ 3	4,837	(47)	(43)	(4)	(855)	37	3,975
Common stock issued										90
Number of Shares Issued									2,580,000
Common stock repurchased										(11)
Common stock repurchased, shares									(292,000)
Common stock reissued
Common stock reissued, shares
Common stock reacquired, value
Common stock reacquired, shares									(245,000)
Stockholder contribution		275
Net gain (loss) arising during the period				(3)				(3)				(8)				(8)
Amortization of net actuarial loss				1				1				2				2
Amortization of prior service credit												(1)				(1)
Unrealized gain (loss) on investments					3			3					1			1
Reclassification adjustments included in net income, net of tax
Other-than-temporary impairment included in net income					2			2					3			3
Net income (loss) attributable to CMS Energy														551		551
Net Income						616		$ 616								553
Dividends declared on common stock						(499)								(345)
Dividends declared on preferred stock						(2)
Income Attributable to Noncontrolling Interests															2	$ 2
Distributions, and other changes in noncontrolling interests															(2)
End of period, shares at Dec. 31, 2016								84,100,000	279,206,000							279,200,000
Total Equity, end at Dec. 31, 2016	841	3,999	(3)	(21)	18	1,065	37	$ 5,939	$ 3	4,916	(50)	(50)		(616)	37	$ 4,290
Cumulative effect of change in accounting principle														33
Common stock issued										102						$ 70
Number of Shares Issued									2,492,000							1,494,371
Common stock repurchased										(14)
Common stock repurchased, shares									(317,000)
Common stock reissued										15
Common stock reissued, shares									360,000
Common stock reacquired, value
Common stock reacquired, shares									(94,000)
Stockholder contribution		450
Net gain (loss) arising during the period				(4)				(4)				(5)				$ (5)
Prior service credit adjustment												4				4
Amortization of net actuarial loss				1				1				2				2
Amortization of prior service credit												(1)				(1)
Unrealized gain (loss) on investments					3			3
Reclassification adjustments included in net income, net of tax					(9)			(9)
Net income (loss) attributable to CMS Energy														460		460
Net Income						632		$ 632								462
Dividends declared on common stock						(522)								(375)
Dividends declared on preferred stock						(2)
Income Attributable to Noncontrolling Interests															2	$ 2
Distributions, and other changes in noncontrolling interests															(2)
End of period, shares at Dec. 31, 2017								84,100,000	281,647,000							281,600,000
Total Equity, end at Dec. 31, 2017	$ 841	$ 4,449	$ (12)	$ (24)	$ 12	$ 1,173	$ 37	$ 6,488	$ 3	$ 5,019	$ (50)	$ (50)		$ (531)	$ 37	$ 4,478