Quarterly Financial and Common Stock Information (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Operating Revenue	$ 1,620		$ 1,464		$ 1,364		$ 2,055		$ 1,682		$ 1,443		$ 1,340		$ 1,967		$ 6,503		$ 6,432		$ 6,205
Operating Income	174		316		207		306		158		319		262		239		1,003		978		698
Income from Continuing Operations	41		140		101		133		31		146		100		89		415		366		220
Income (Loss) From Discontinued Operations, Net of Tax							2		(6)				(16)		(1)		2	[1]	(23)	[2]	20	[3]
Net Income	41		140		101		135		25		146		84		88		417		343		240
Income attributable to noncontrolling interests			1		1						1		2				2		3		11
Net Income Attributable to CMS Energy	41		139		100		135		25		145		82		88		415		340		229
Charge for Deferred Issuance Costs on Preferred Stock											8						0		8		0
Preferred Stock Dividends											3		2		3		0		8		11
Net Income Available to Common Stockholders	41		139		100		135		25		134		80		85		415		324		218
Earnings from continuing operations per average common share - basic	$ 0.16		$ 0.55		$ 0.40		$ 0.53		$ 0.13	[4]	$ 0.58	[4]	$ 0.42	[4]	$ 0.38	[4]	$ 1.65		$ 1.50		$ 0.87
Earnings from continuing operations per average common share - diluted	$ 0.15		$ 0.53		$ 0.38		$ 0.51		$ 0.11	[4]	$ 0.53	[4]	$ 0.39	[4]	$ 0.35	[4]	$ 1.57		$ 1.36		$ 0.83
Basic earnings per average common share	$ 0.16	[4]	$ 0.55	[4]	$ 0.40	[4]	$ 0.54	[4]	$ 0.11	[4]	$ 0.58	[4]	$ 0.35	[4]	$ 0.37	[4]	$ 1.66		$ 1.40		$ 0.96
Diluted earnings per average common share	$ 0.15	[4]	$ 0.53	[4]	$ 0.38	[4]	$ 0.52	[4]	$ 0.09	[4]	$ 0.53	[4]	$ 0.32	[4]	$ 0.34	[4]	$ 1.58		$ 1.28		$ 0.91
CMS Energy Corporation [Member]
Operating Income																	(3)		(6)		(10)
Income from Continuing Operations																	415		350		229
Income (Loss) From Discontinued Operations, Net of Tax																			(10)
Net Income																	415		340		229
Charge for Deferred Issuance Costs on Preferred Stock																			8
Preferred Stock Dividends																			8		11
Net Income Available to Common Stockholders																	415		324		218
Consumers Energy Company [Member]
Operating Revenue	1,565		1,397		1,303		1,988		1,620		1,370		1,276		1,890		6,253		6,156		5,963
Operating Income	173		305		207		300		191		304		207		224		985		926		689
Net Income	67		155		92		153		79		160		88		107		467		434		293
Preferred Stock Dividends			1		1						1		1				2		2		2
Net Income Available to Common Stockholders	$ 67		$ 154		$ 91		$ 153		$ 79		$ 159		$ 87		$ 107		$ 465		$ 432		$ 291
Maximum [Member] | CMS Energy Common Stock [Member]
Share price	$ 22.35	[5]	$ 20.47	[5]	$ 20.39	[5]	$ 19.78	[5]	$ 19.16	[5]	$ 18.15	[5]	$ 16.55	[5]	$ 15.90	[5]
Minimum [Member] | CMS Energy Common Stock [Member]
Share price	$ 19.18	[5]	$ 17.16	[5]	$ 18.90	[5]	$ 18.60	[5]	$ 17.72	[5]	$ 14.68	[5]	$ 14.26	[5]	$ 14.57	[5]

[1] Includes an operating gain of $3 million related to a litigation settlement at CMS Viron.

[2] Includes an operating loss of $2 million ($1 million net of tax) at Exeter, whose assets and liabilities were reclassified as held for sale in 2009. Also includes disposal-related losses of $10 million in additional tax expense resulting from an IRS audit adjustment related to a 2003 asset sale, a $6 million ($4 million net of tax) loss for the write down of CMS Energy's investment in Exeter, a $5 million ($3 million net of tax) loss for the increase in a liability for a 2007 asset sale, and a $5 million ($3 million net of tax) loss on the settlement of a 2002 asset sale indemnity.

[3] Includes an operating loss of $11 million ($7 million net of tax) at Exeter and a loss of $3 million ($2 million net of tax) related to a litigation settlement at CMS Viron. Also includes a gain for the expiration of an indemnity obligation related to a 2007 asset sale. CMS Energy provided an indemnity to TAQA in connection with the sale of its ownership interests in businesses in the Middle East, Africa, and India, and recorded a $50 million provision for the contingent liability. This indemnity expired in 2009 and CMS Energy eliminated the liability from its consolidated balance sheets, recognizing a $45 million benefit ($28 million net of tax) to income (loss) from discontinued operations and a $5 million benefit to gain on asset sales, net.

[4]

[5] Based on New York Stock Exchange composite transactions.