Earnings Per Share - CMS Energy (Basic And Diluted EPS Computations) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income available to common stockholders
Income from continuing operations	$ 114	$ 153	$ 153	$ 308	$ 138	$ 198	$ 129	$ 229	$ 728	$ 694	$ 633
Income (loss) attributable to noncontrolling interests	$ (5)	$ (6)	$ (5)	$ (7)	$ 4	$ (8)	$ 1	$ 0	(23)	(3)	2
Preferred stock dividends									5	0	0
Income from continuing operations available to common stockholders – basic and diluted									$ 746	$ 697	$ 631
Average common shares outstanding
Weighted average shares - basic (in shares)									289.0	285.0	283.0
Dilutive nonvested stock awards (in shares)									0.5	0.7	0.7
Dilutive forward equity sale contracts (in shares)									0.0	0.6	0.6
Weighted average shares - diluted (in shares)									289.5	286.3	284.3
Income from continuing operations per average common share available to common stockholders - Basic (in dollars per share)	$ 0.40	$ 0.54	$ 0.55	$ 1.09	$ 0.47	$ 0.72	$ 0.45	$ 0.81	$ 2.58	$ 2.45	$ 2.23
Income from continuing operations per average common share available to common stockholders - Diluted (in dollars per share)	$ 0.40	$ 0.54	$ 0.55	$ 1.09	$ 0.47	$ 0.72	$ 0.45	$ 0.80	$ 2.58	$ 2.44	$ 2.22