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, 2012	$ 841	$ 3,107	$ (4)	$ (18)	$ 14	$ 515	$ 44	$ 4,503	$ 3	$ 4,641	$ (47)	$ (47)	$ 1	$ (1)	$ (1,548)	$ 44	$ 3,093
Common stock issued										23
Common stock reissued
Stockholder contribution
Retirement benefits liability adjustments												1					(1)
Unrealized gain (loss) on investments, net of tax					3			3					1				1
Reclassification adjustments included in net income, net of tax
Net income attributable to CMS Energy															100
Net income						122		122									101
Common stock dividends declared						(43)									(63)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions and other changes in noncontrolling interests																(1)
Total Equity, end 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
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										31
Common stock reissued										6
Stockholder contribution		150						150
Retirement benefits liability adjustments				1				(1)				2					(2)
Unrealized gain (loss) on investments, net of tax													2				2
Reclassification adjustments included in net income, net of tax
Net income attributable to CMS Energy															167
Net income						198		198									168
Common stock dividends declared						(158)									(125)
Preferred stock dividends and distributions declared						(1)
Income attributable to noncontrolling interests																1	1
Distributions and other changes in noncontrolling interests																(1)
Total Equity, end 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
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										37
Common stock reissued										5
Common stock repurchased										(1)
Stockholder contribution		150						150
Retirement benefits liability adjustments				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
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 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 Mar. 31, 2013	841	3,257	(6)	(24)	18	667	44	4,803	3	4,703	(54)	(55)	2	(1)	(1,346)	44	3,350
Common stock issued										8
Common stock reissued
Common stock repurchased										(1)
Stockholder contribution
Retirement benefits liability adjustments				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
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 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