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, 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										8
Common stock reissued										6
Stockholder contribution		150						150
Retirement benefits liability adjustments				1								1
Unrealized gain (loss) on investments					(3)			(3)					1				1
Reclassification adjustments included in net income, net of tax
Net income						76		76							67		67
Common stock dividends declared						(115)									(62)
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
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										29							20
Common stock reissued										5
Stockholder contribution		150						150
Retirement benefits liability adjustments				1								1
Unrealized gain (loss) on investments					4			4
Reclassification adjustments included in net income, net of tax					(3)			(3)
Net income						162		162							144		144
Common stock dividends declared						(93)									(67)
Total Equity, end 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