Consolidated Statements Of Changes In Equity - USD ($) shares in Thousands, $ 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 Income (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 Income (Loss) [Member]	Retirement Benefits Liability [Member]	Investments [Member]	Derivative Instruments [Member]	Retained Earnings (Accumulated Deficit) [Member]	Noncontrolling Interest [Member]	Total
Total Equity, beginning at Dec. 31, 2012	$ 841	$ 3,107	$ (8)	$ (25)	$ 17	$ 598	$ 44	$ 4,582	$ 3	$ 4,669	$ (55)	$ (56)	$ 2	$ (1)	$ (1,423)	$ 44	$ 3,238
Beginning of period, shares at Dec. 31, 2012									264,072
Common stock issued										51
Number of Shares Issued									2,238
Common stock repurchased										(10)
Common stock repurchased, shares									(356)
Common stock reissued										$ 5
Common stock reissued, shares									205
Conversion option on convertible debt
Common stock reacquired, value
Common stock reacquired, shares									(22)
Stockholder contribution		$ 150
Return of stockholder contribution
Net gain arising during the period				5				5				26					26
Prior service credit adjustment												5					5
Amortization of net actuarial loss (gain)				3				3				4					4
Unrealized gain (loss) on investments, net of tax					1			1					$ (2)				(2)
Reclassification adjustments included in net income, net of tax					(3)			3
Reclassification adjustments included in net income
Net income (loss) attributable to CMS Energy															452		452
Net income						534		534									454
Dividends declared on common stock						(406)									(271)
Preferred stock dividends and distributions declared						(2)
Income Attributable to Noncontrolling Interests																2	2
Distributions, redemptions, and other changes in noncontrolling interests																(9)
Preferred stock redeemed							(7)
End of period, shares at Dec. 31, 2013									266,137
Total Equity, end at Dec. 31, 2013	841	$ 3,257	(2)	(17)	15	724	$ 37	4,857	$ 3	$ 4,715	(22)	(21)		$ (1)	(1,242)	37	3,491
Common stock issued										59
Number of Shares Issued									9,371
Common stock repurchased										$ (7)
Common stock repurchased, shares									(271)
Common stock reissued
Common stock reissued, shares
Conversion option on convertible debt										$ 7
Common stock reacquired, value
Common stock reacquired, shares									(53)
Stockholder contribution		495
Return of stockholder contribution		(178)
Net gain arising during the period				(11)				(11)				$ (29)					(29)
Prior service credit adjustment
Amortization of net actuarial loss (gain)				2				2				$ 3					3
Amortization of prior service credit												(1)					(1)
Unrealized gain (loss) on investments, net of tax					$ 4			4					$ (1)				(1)
Reclassification adjustments included in net income, net of tax
Reclassification adjustments included in net income														$ 1			(1)
Net income (loss) attributable to CMS Energy															477		477
Net income						567		$ 567									479
Dividends declared on common stock						(457)									(293)
Preferred stock dividends and distributions declared						(2)
Income Attributable to Noncontrolling Interests																2	$ 2
Distributions, redemptions, and other changes in noncontrolling interests																(2)
Preferred stock redeemed
End of period, shares at Dec. 31, 2014								84,100	275,184								275,200
Total Equity, end 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
Common stock issued										65
Number of Shares Issued									2,062
Common stock repurchased										(12)
Common stock repurchased, shares									(306)
Common stock reissued										$ 10
Common stock reissued, shares									288
Conversion option on convertible debt
Common stock reacquired, value
Common stock reacquired, shares									(65)
Stockholder contribution		$ 150
Return of stockholder contribution
Net gain arising during the period				3				3				$ 1					1
Prior service credit adjustment
Amortization of net actuarial loss (gain)				4				4				$ 5					5
Amortization of prior service credit												(1)					(1)
Unrealized gain (loss) on investments, net of tax					(1)			(1)					(3)				(3)
Reclassification adjustments included in net income, net of tax					(5)			5
Reclassification adjustments included in net income
Net income (loss) attributable to CMS Energy															523		523
Net income						594		$ 594									525
Dividends declared on common stock						(474)									(320)
Preferred stock dividends and distributions declared						(2)
Income Attributable to Noncontrolling Interests																2	$ 2
Distributions, redemptions, and other changes in noncontrolling interests																(2)
Preferred stock redeemed
End of period, shares at Dec. 31, 2015								84,100	277,163								277,200
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