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 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	6
Common stock reissued										5
Stockholders contribution		125						125
Retirement benefits liability adjustments, net of tax				1				(1)				0					0
Unrealized gain (loss) on investments, net of tax					(1)			(1)					0				0
Net income						153		153							135		135
Common stock dividends declared						(104)									(53)
Distributions and other changes in noncontrolling interests																0
Total Equity, end 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
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										8
Common stock reissued										6
Stockholders contribution		150						150
Retirement benefits liability adjustments, net of tax				1				(1)				1					(1)
Unrealized gain (loss) on investments, net of tax					(3)			(3)					1				1
Net income						76		76							67		67
Common stock dividends declared						(115)									(62)
Distributions and other changes in noncontrolling interests																0
Total Equity, end 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