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, 2012	$ 841	$ 3,107	$ (1)	$ (18)	$ 17	$ 593	$ 44	$ 4,584	$ 3	$ 4,664	$ (45)	$ (46)	$ 2	$ (1)	$ (1,511)	$ 44	$ 3,155
Common stock issued										7
Common stock reissued
Common stock repurchased										(9)
Stockholder contribution
Amortization of net actuarial loss				1				1				1					1
Unrealized gain (loss) on investments, net of tax													1				1
Reclassification adjustments included in net income, net of tax
Net income attributable to CMS Energy															148
Net income						163		163									149
Common stock dividends declared						(144)									(63)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions and other changes in noncontrolling interests																(1)
Preferred stock redeemed
Total Equity, end at Sep. 30, 2012	841	3,107		(17)	17	611	44	4,603	3	4,662	(43)	(45)	3	(1)	(1,426)	44	3,240
Total Equity, beginning at Dec. 31, 2011	841	2,957	(2)	(19)	17	554	44	4,394	3	4,627	(49)	(48)		(1)	(1,553)	44	3,072
Common stock issued										38
Common stock reissued										6
Common stock repurchased										(9)
Stockholder contribution		150						150
Amortization of net actuarial loss				2				2				3					3
Unrealized gain (loss) on investments, net of tax													3				3
Reclassification adjustments included in net income, net of tax
Net income attributable to CMS Energy															315
Net income						361		361									317
Common stock dividends declared						(302)									(188)
Preferred stock dividends and distributions declared						(2)
Income attributable to noncontrolling interests																2	2
Distributions and other changes in noncontrolling interests																(2)
Preferred stock redeemed
Total Equity, end at Sep. 30, 2012	841	3,107		(17)	17	611	44	4,603	3	4,662	(43)	(45)	3	(1)	(1,426)	44	3,240
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
Common stock issued										44
Common stock reissued										5
Common stock repurchased										(10)
Stockholder contribution		150						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
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 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 Jun. 30, 2013	841	3,257	(9)	(23)	14	665	37	4,791	3	4,710	(56)	(54)	(1)	(1)	(1,334)	37	3,360
Common stock issued										7
Common stock reissued
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
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 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