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] Comprehensive Income [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]	Preferred Stock [Member]	Noncontrolling Interest [Member]	Comprehensive Income [Member]	Total
Total Equity, beginning at Mar. 31, 2010	$ 841	$ 2,782	$ (1)	$ (11)	$ 12	$ 382	$ 44		$ 4,132	$ 2	$ 4,564	$ (32)	$ (31)	$ 0	$ (1)	$ (1,876)	$ 239	$ 44		$ 2,941
Common stock issued											6
Common stock repurchased											(1)
Stockholder's contribution		50
Income attributable to noncontrolling interests																		2	2	2
Retirement benefits liability adjustments, net of tax								0					1						1
Unrealized gain (loss) on investments, net of tax					(1)			(1)						0					0
Net Income						88		88	88							82			84	84
Common stock dividends declared						(54)										(35)
Preferred stock dividends declared						(1)										(2)
Distributions and other changes in noncontrolling interests																		(1)
Net Income Attributable to CMS Energy																			82	82
Total Comprehensive Income								87											83
Total Equity, end at Jun. 30, 2010	841	2,832	0	(11)	11	415	44		4,132	2	4,569	(31)	(30)	0	(1)	(1,831)	239	45		2,993
Total Equity, beginning at Dec. 31, 2009	841	2,582	(2)	(11)	13	389	44		3,858	2	4,560	(33)	(32)	0	(1)	(1,927)	239	97		2,938
Common stock issued											10
Common stock repurchased											(1)
Stockholder's contribution		250							250
Income attributable to noncontrolling interests																		2	2	2
Retirement benefits liability adjustments, net of tax								0					2						2
Unrealized gain (loss) on investments, net of tax					(2)			(2)						0					0
Net Income						195		195	195							170			172	172
Common stock dividends declared						(168)										(69)
Preferred stock dividends declared						(1)										(5)
Distributions and other changes in noncontrolling interests																		(54)
Net Income Attributable to CMS Energy																			170	170
Total Comprehensive Income								193											172
Total Equity, end at Jun. 30, 2010	841	2,832	0	(11)	11	415	44		4,132	2	4,569	(31)	(30)	0	(1)	(1,831)	239	45		2,993
Total Equity, beginning at Dec. 31, 2010	841	2,832	0	(16)	16	463	44		4,180	2	4,588	(40)	(39)	0	(1)	(1,757)	0	44		2,837
Common stock issued										1	28
Common stock repurchased											0
Common stock reissued, value											5
Stockholder's contribution		125							125
Income attributable to noncontrolling interests																		1	1	1
Retirement benefits liability adjustments, net of tax				1				1					1						1
Unrealized gain (loss) on investments, net of tax					(1)			(1)						1					1
Net Income						245		245	245							229			236	236
Common stock dividends declared						(196)										(106)
Preferred stock dividends declared						(1)										0
Distributions and other changes in noncontrolling interests																		(1)
Net Income Attributable to CMS Energy																			235	235
Total Comprehensive Income								245											237
Total Equity, end at Jun. 30, 2011	841	2,957	0	(15)	15	511	44		4,353	3	4,621	(38)	(38)	1	(1)	(1,628)	0	44		3,002
Total Equity, beginning at Mar. 31, 2011	841	2,957	0	(15)	15	512	44		4,354	3	4,599	(40)	(39)	0	(1)	(1,675)	0	44		2,931
Common stock issued											22
Common stock repurchased											0
Common stock reissued, value											0
Stockholder's contribution		0
Income attributable to noncontrolling interests																		1	1	1
Retirement benefits liability adjustments, net of tax								0					1						1
Unrealized gain (loss) on investments, net of tax					0			0						1					1
Net Income						92		92	92							100			101	101
Common stock dividends declared						(92)										(53)
Preferred stock dividends declared						(1)										0
Distributions and other changes in noncontrolling interests																		(1)
Net Income Attributable to CMS Energy																			100	100
Total Comprehensive Income								92											102
Total Equity, end at Jun. 30, 2011	$ 841	$ 2,957	$ 0	$ (15)	$ 15	$ 511	$ 44		$ 4,353	$ 3	$ 4,621	$ (38)	$ (38)	$ 1	$ (1)	$ (1,628)	$ 0	$ 44		$ 3,002