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, 2011	$ 841	$ 2,957	$ 0	$ (15)	$ 15	$ 512	$ 44	$ 4,354	$ 3	$ 4,599	$ (40)	$ (39)	$ 0	$ (1)	$ (1,675)	$ 44	$ 2,931
Common stock issued										22
Common stock reissued										0
Stockholders contribution		0
Income attributable to noncontrolling interests																1	1
Retirement benefits liability adjustments, net of tax												1					1
Unrealized gain (loss) on investments, net of tax					0								1				1
Net income						92		92							100		101
Common stock dividends declared						(92)									(53)
Preferred stock dividends declared						(1)
Distributions and other changes in noncontrolling interests																(1)
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)	44	3,002
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)	44	2,837
Common stock issued									1	28
Common stock reissued										5
Stockholders contribution		125						125
Income attributable to noncontrolling interests																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							235		236
Common stock dividends declared						(196)									(106)
Preferred stock dividends declared						(1)
Distributions and other changes in noncontrolling interests																(1)
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)	44	3,002
Total Equity, beginning at Dec. 31, 2011	841	2,957	(2)	(19)	17	554	44	4,394	3	4,627	(49)	(48)	0	(1)	(1,553)	44	3,072
Common stock issued										31
Common stock reissued										6
Stockholders contribution		150						150
Income attributable to noncontrolling interests																1	1
Retirement benefits liability adjustments, net of tax				1				1				2					2
Unrealized gain (loss) on investments, net of tax					0								2				2
Net income						198		198							167		168
Common stock dividends declared						(158)									(125)
Preferred stock dividends declared						(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 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
Stockholders contribution		0
Income attributable to noncontrolling interests																1	1
Retirement benefits liability adjustments, net of tax												1					1
Unrealized gain (loss) on investments, net of tax					3			3					1				1
Net income						122		122							100		101
Common stock dividends declared						(43)									(63)
Preferred stock dividends declared						(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