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 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 Jun. 30, 2013		$ 3,257	$ (9)	$ (23)	$ 14	$ 665	$ 37	$ 4,791		$ 4,710	$ (56)	$ (54)	$ (1)	$ (1)	$ (1,334)	$ 37	$ 3,360
Common stock issued										7
Common stock repurchased										(9)
Stockholder contribution
Net gain arising during the period												10					10
Prior service credit adjustment												5					5
Amortization of net actuarial loss												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															126
Net income						153		153									127
Common stock dividends declared						(106)									(68)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions, redemptions, and other changes in noncontrolling interests																(1)
Preferred stock redeemed
Total Equity, end at Sep. 30, 2013	841	3,257	(9)	(23)	14	711	37	4,837	3	4,708	(39)	(38)		(1)	(1,276)	37	3,433
Total Equity, beginning at Dec. 31, 2012		3,107	(8)	(25)	17	598	44	4,582		4,669	(55)	(56)	2	(1)	(1,423)	44	3,238
Common stock issued										44
Common stock repurchased										(10)
Common stock reissued										5
Stockholder contribution		150
Net gain arising during the period												10					10
Prior service credit adjustment												5					5
Amortization of net actuarial loss				2				2				3					3
Unrealized gain (loss) on investments, net of tax													(2)				(2)
Reclassification adjustments included in net income, net of tax					(3)			3
Reclassification adjustments included in net income
Net income attributable to CMS Energy															350
Net income						415		415									352
Common stock dividends declared						(300)									(203)
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)
Total Equity, end at Sep. 30, 2013	841	3,257	(9)	(23)	14	711	37	4,837	3	4,708	(39)	(38)		(1)	(1,276)	37	3,433
Total Equity, beginning at Dec. 31, 2013		3,257	(2)	(17)	15	724	37	4,857		4,715	(22)	(21)		(1)	(1,242)	37	3,491
Common stock issued										52
Common stock repurchased										(7)
Conversion option on convertible debt										7
Stockholder contribution		495
Return of stockholder contribution		(178)
Amortization of net actuarial loss				2				2				2					2
Amortization of prior service credit												(1)					(1)
Unrealized gain (loss) on investments, net of tax					2			2
Reclassification adjustments included in net income, net of tax
Reclassification adjustments included in net income														1			(1)
Net income attributable to CMS Energy															381
Net income						449		449									382
Common stock dividends declared						(375)									(219)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions, redemptions, and other changes in noncontrolling interests																(1)
Preferred stock redeemed
Total Equity, end at Sep. 30, 2014	841	3,574	2	(15)	17	797	37	5,251	3	4,767	(20)	(20)			(1,080)	37	3,707
Total Equity, beginning at Jun. 30, 2014		3,572	2	(16)	18	798	37	5,250		4,761	(20)	(20)			(1,099)	37	3,682
Common stock issued										7
Common stock repurchased										(1)
Stockholder contribution		180
Return of stockholder contribution		(178)
Amortization of net actuarial loss				1				1				1					1
Amortization of prior service credit												(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															94
Net income						119		119									94
Common stock dividends declared						(120)									(75)
Distributions, redemptions, and other changes in noncontrolling interests
Preferred stock redeemed
Total Equity, end at Sep. 30, 2014	$ 841	$ 3,574	$ 2	$ (15)	$ 17	$ 797	$ 37	$ 5,251	$ 3	$ 4,767	$ (20)	$ (20)			$ (1,080)	$ 37	$ 3,707