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 Mar. 31, 2013		$ 3,257	$ (6)	$ (24)	$ 18	$ 667	$ 44	$ 4,803		$ 4,703	$ (54)	$ (55)	$ 2	$ (1)	$ (1,346)	$ 44	$ 3,350
Common stock issued										8
Common stock repurchased										(1)
Stockholder contribution
Amortization of net actuarial loss				1				1				1					1
Unrealized gain (loss) on investments, net of tax					(4)			(4)					(3)				(3)
Reclassification adjustments included in net income, net of tax
Reclassification adjustments included in net income
Net income attributable to CMS Energy															80
Net income						100		100									81
Common stock dividends declared						(101)									(68)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions, redemptions, and other changes in noncontrolling interests																(8)
Preferred stock redeemed							(7)
Total Equity, end 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
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										37
Common stock repurchased										(1)
Common stock reissued										5
Stockholder contribution		150						150
Amortization of net actuarial loss				2				2				2					2
Unrealized gain (loss) on investments, net of tax													(3)				(3)
Reclassification adjustments included in net income, net of tax					(3)			3
Reclassification adjustments included in net income
Net income attributable to CMS Energy															224
Net income						262		262									225
Common stock dividends declared						(194)									(135)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions, redemptions, and other changes in noncontrolling interests																(8)
Preferred stock redeemed							(7)
Total Equity, end 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
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										45
Common stock repurchased										(6)
Conversion option on convertible debt										7
Stockholder contribution		315						315
Amortization of net actuarial loss				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									288
Common stock dividends declared						(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		3,407		(17)	17	810	37	5,095		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				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									84
Common stock dividends declared						(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