Consolidated Statements Of Changes In Equity (USD $) In Millions, except Share data	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, 2011	$ 841	$ 2,957	$ (2)	$ (19)	$ 17	$ 554	$ 44	$ 4,394	$ 3	$ 4,627	$ (49)	$ (48)		$ (1)	$ (1,553)	$ 44	$ 3,072
Beginning of period, shares at Dec. 31, 2011									254,100,000
Common stock issued										45
Number of Shares Issued									10,107,000
Common stock repurchased										(9)
Common stock repurchased, shares									(389,000)
Common stock reissued										6
Common stock reissued, shares									272,000
Conversion option on convertible debt
Common stock reacquired, value
Common stock reacquired, shares									(18,000)
Stockholder contribution		150
Return of stockholder contribution
Net gain arising during the period				(8)				(8)				(10)					(10)
Prior service credit adjustment
Amortization of net actuarial loss				2				2				2					2
Unrealized gain (loss) on investments, net of tax					3			3					2				2
Reclassification adjustments included in net income, net of tax					(3)			3
Net income attributable to CMS Energy															382		382
Net income						439		439									384
Common stock dividends declared						(393)									(252)
Preferred stock dividends and distributions declared						(2)
Income attributable to noncontrolling interests																2	2
Distributions, redemptions, and other changes in noncontrolling interests																(2)
Preferred stock redeemed
Total Equity, end 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
End of period, shares at Dec. 31, 2012									264,072,000
Net income attributable to CMS Energy																	144
Net income								162									144
Total Equity, end at Mar. 31, 2013
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
Beginning of period, shares at Dec. 31, 2012									264,072,000
Common stock issued										51
Number of Shares Issued									2,238,000
Common stock repurchased										(10)
Common stock repurchased, shares									(356,000)
Common stock reissued										5
Common stock reissued, shares									205,000
Conversion option on convertible debt
Common stock reacquired, value
Common stock reacquired, shares									(22,000)
Stockholder contribution		150
Return of stockholder contribution
Net gain arising during the period				5				5				26					26
Prior service credit adjustment												5					5
Amortization of net actuarial loss				3				3				4					4
Unrealized gain (loss) on investments, net of tax					1			1					(2)				(2)
Reclassification adjustments included in net income, net of tax					(3)			3
Net income attributable to CMS Energy															452		452
Net income						534		534									454
Common stock dividends declared						(406)									(271)
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 Dec. 31, 2013	841	3,257	(2)	(17)	15	724	37	4,857	3	4,715	(22)	(21)			(1,242)	37	3,491
End of period, shares at Dec. 31, 2013								84,100,000	266,137,000								266,100,000
Total Equity, beginning at Sep. 30, 2013
Net income attributable to CMS Energy																	102
Net income								119									102
Total Equity, end at Dec. 31, 2013	841		(2)					4,857			(22)						3,491
End of period, shares at Dec. 31, 2013								84,100,000									266,100,000
Common stock issued																	30
Number of Shares Issued																	1,070,080
Net income attributable to CMS Energy																	204
Net income								221									204
Total Equity, end at Mar. 31, 2014
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
Beginning of period, shares at Dec. 31, 2013								84,100,000	266,137,000								266,100,000
Common stock issued										59
Number of Shares Issued									9,371,000
Common stock repurchased										(7)
Common stock repurchased, shares									(271,000)
Common stock reissued
Common stock reissued, shares
Conversion option on convertible debt										7
Common stock reacquired, value
Common stock reacquired, shares									(53,000)
Stockholder contribution		495
Return of stockholder contribution		(178)
Net gain arising during the period				(11)				(11)				(29)					(29)
Prior service credit adjustment
Amortization of net actuarial loss				2				2				3					3
Amortization of prior service credit												(1)					(1)
Unrealized gain (loss) on investments, net of tax					4			4					(1)				(1)
Reclassification adjustments included in net income, net of tax
Reclassification adjustments included in net income														1			(1)
Net income attributable to CMS Energy															477		477
Net income						567		567									479
Common stock dividends declared						(457)									(293)
Preferred stock dividends and distributions declared						(2)
Income attributable to noncontrolling interests																2	2
Distributions, redemptions, and other changes in noncontrolling interests																(2)
Preferred stock redeemed
Total Equity, end 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
End of period, shares at Dec. 31, 2014								84,100,000	275,184,000								275,200,000
Total Equity, beginning at Sep. 30, 2014
Net income attributable to CMS Energy																	96
Net income								118									97
Income attributable to noncontrolling interests																	1
Total Equity, end at Dec. 31, 2014	$ 841		$ (7)					$ 5,277			$ (49)						$ 3,707
End of period, shares at Dec. 31, 2014								84,100,000									275,200,000