Quarterly Financial And Common Stock Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Operating Revenue		$ 1,640		$ 1,587		$ 1,371		$ 1,801		$ 1,509		$ 1,486		$ 1,350		$ 2,111		$ 6,399	$ 6,456	$ 7,179
Operating Income (Loss)		290		386		285		336		245		317		204		397		1,297	1,163	1,152
Net Income		78		186		125		164		107		148		68		202		553	525	479
Income Attributable to Noncontrolling Interests		1				1				1				1				2	2	2
Net income attributable to CMS Energy		$ 77		$ 186		$ 124		$ 164		$ 106		$ 148		$ 67		$ 202		$ 551	$ 523	$ 477
Basic Earnings Per Average Common Share		$ 0.28	[1]	$ 0.67	[1]	$ 0.45	[1]	$ 0.59	[1]	$ 0.39	[1]	$ 0.53	[1]	$ 0.25	[1]	$ 0.73	[1]	$ 1.99	$ 1.90	$ 1.76
Diluted Earnings Per Average Common Share		$ 0.28	[1]	$ 0.67	[1]	$ 0.45	[1]	$ 0.59	[1]	$ 0.38	[1]	$ 0.53	[1]	$ 0.25	[1]	$ 0.73	[1]	$ 1.98	$ 1.89	$ 1.74
CMS Energy [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Operating Income (Loss)																		$ (15)	$ (9)	$ (6)
Net Income																		551	523	477
Net income attributable to CMS Energy																		551	523	477
Consumers Energy Company [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Operating Revenue		$ 1,550		$ 1,498		$ 1,293		$ 1,723		$ 1,439		$ 1,417		$ 1,281		$ 2,028		6,064	6,165	6,800
Operating Income (Loss)		288		365		264		317		246		305		192		379		1,234	1,122	1,135
Net Income		117		195		132		172		135		160		84		215		616	594	567
Preferred stock dividends		1				1				1				1				2	2	2
Net income (loss) available to common stockholder		$ 116		$ 195		$ 131		$ 172		$ 134		$ 160		$ 83		$ 215		$ 614	$ 592	$ 565
Maximum [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Share price	[2]	$ 42.15		$ 46.17		$ 45.86		$ 42.44		$ 37.17		$ 35.82		$ 35.57		$ 38.20		$ 42.15	$ 37.17
Minimum [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Share price	[2]	$ 39.49		$ 41.31		$ 39.38		$ 35.61		$ 34.24		$ 32.10		$ 31.39		$ 32.83		$ 39.49	$ 34.24

[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.