Consolidated Statements Of Changes In Equity - USD ($) shares in Millions, $ 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, 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										45
Common stock repurchased										(6)
Conversion option on convertible debt										7
Stockholder contribution		315
Amortization of net actuarial loss (gain)				1				1				1					1
Unrealized gain (loss) on investments, net of tax					$ 3			3
Reclassification adjustments included in net income, net of tax
Reclassification adjustments included in net income														$ 1			(1)
Net income attributable to CMS Energy																	287
Net income						330		330							287		288
Dividends declared on common stock						(255)									(144)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions, redemptions, and other changes in noncontrolling interests																(1)
Total Equity, end at Jun. 30, 2014	841	3,572	2	(16)	$ 18	798	37	5,250	3	4,761	(20)	(20)			(1,099)	37	3,682
Total Equity, beginning at Mar. 31, 2014	841	3,407		(17)	17	810	37	5,095	3	4,746	(21)	(21)			(1,110)	37	3,655
Common stock issued										$ 8
Common stock repurchased
Conversion option on convertible debt										$ 7
Stockholder contribution		165
Amortization of net actuarial loss (gain)				1				1				1					1
Unrealized gain (loss) on investments, net of tax					$ 1			1
Reclassification adjustments included in net income, net of tax
Reclassification adjustments included in net income
Net income attributable to CMS Energy																	83
Net income						109		109							83		84
Dividends declared on common stock						(120)									(72)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions, redemptions, and other changes in noncontrolling interests																(1)
Total Equity, end at Jun. 30, 2014	841	3,572	2	(16)	$ 18	798	37	5,250	3	4,761	(20)	(20)			(1,099)	37	3,682
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								84.1									275.2
Common stock issued										39
Common stock repurchased										(11)
Common stock reissued										10
Stockholder contribution		150
Amortization of net actuarial loss (gain)				2				$ 2				2					$ 2
Unrealized gain (loss) on investments, net of tax					(2)			(2)					(1)				(1)
Reclassification adjustments included in net income, net of tax					(5)			5
Reclassification adjustments included in net income
Net income attributable to CMS Energy																	269
Net income						299		$ 299							269		270
Dividends declared on common stock						(254)									(160)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	$ 1
Distributions, redemptions, and other changes in noncontrolling interests																(1)
End of period, shares at Jun. 30, 2015								84.1									276.7
Total Equity, end at Jun. 30, 2015	841	3,724	(12)	(24)	12	876	37	$ 5,466	3	4,812	(48)	(46)	(2)		(949)	37	$ 3,855
Total Equity, beginning at Mar. 31, 2015	841	$ 3,724	(11)	(25)	14	925	37	5,516	3	4,783	(48)	(47)	(1)		(936)	37	3,839
Common stock issued										$ 29
Common stock repurchased
Stockholder contribution
Amortization of net actuarial loss (gain)				1				1				1					1
Unrealized gain (loss) on investments, net of tax					$ (2)			(2)					(1)				(1)
Reclassification adjustments included in net income, net of tax
Reclassification adjustments included in net income
Net income attributable to CMS Energy																	67
Net income						84		$ 84							67		68
Dividends declared on common stock						(132)									(80)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	$ 1
Distributions, redemptions, and other changes in noncontrolling interests																(1)
End of period, shares at Jun. 30, 2015								84.1									276.7
Total Equity, end at Jun. 30, 2015	$ 841	$ 3,724	$ (12)	$ (24)	$ 12	$ 876	$ 37	$ 5,466	$ 3	$ 4,812	$ (48)	$ (46)	$ (2)		$ (949)	$ 37	$ 3,855