Quarterly Financial And Common Stock Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Operating Revenue		$ 1,509		$ 1,486		$ 1,350		$ 2,111		$ 1,758		$ 1,430		$ 1,468		$ 2,523		$ 6,456	$ 7,179	$ 6,566
Operating Income (Loss)		245		317		204		397		273		236		235		408		1,163	1,152	1,142
Net Income		107		148		68		202		97		94		84		204		525	479	454
Income Attributable to Noncontrolling Interests		1				1				1				1				2	2	2
Net income (loss) attributable to CMS Energy		$ 106		$ 148		$ 67		$ 202		$ 96		$ 94		$ 83		$ 204		$ 523	$ 477	$ 452
Basic Earnings Per Average Common Share		$ 0.39	[1]	$ 0.53	[1]	$ 0.25	[1]	$ 0.73	[1]	$ 0.35	[1]	$ 0.34	[1]	$ 0.31	[1]	$ 0.77	[1]	$ 1.90	$ 1.76	$ 1.71
Diluted Earnings Per Average Common Share		$ 0.38	[1]	$ 0.53	[1]	$ 0.25	[1]	$ 0.73	[1]	$ 0.35	[1]	$ 0.34	[1]	$ 0.30	[1]	$ 0.75	[1]	$ 1.89	$ 1.74	$ 1.66
CMS Energy [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Operating Income (Loss)																		$ (9)	$ (6)	$ (6)
Net Income																		523	477	452
Net income (loss) attributable to CMS Energy																		523	477	452
Consumers Energy Company [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Operating Revenue		$ 1,439		$ 1,417		$ 1,281		$ 2,028		$ 1,672		$ 1,359		$ 1,387		$ 2,382		6,165	6,800	6,321
Operating Income (Loss)		246		305		192		379		264		245		227		399		1,122	1,135	1,118
Net Income		135		160		84		215		118		119		109		221		594	567	534
Preferred stock dividends		1				1				1				1				2	2	2
Net Income Available to Common Stockholders		$ 134		$ 160		$ 83		$ 215		$ 117		$ 119		$ 108		$ 221		$ 592	$ 565	$ 532
Maximum [Member] | CMS Energy Common Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Share price	[2]	$ 37.17		$ 35.82		$ 35.57		$ 38.20		$ 36.42		$ 30.87		$ 31.15		$ 29.28		$ 37.17	$ 36.42
Minimum [Member] | CMS Energy Common Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Share price	[2]	$ 34.24		$ 32.10		$ 31.39		$ 32.83		$ 29.78		$ 28.18		$ 28.87		$ 26.12		$ 34.24	$ 29.78

[1] The sum of the quarters may not equal annual EPS due to changes in the number of shares outstanding.

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