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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income available to common stockholders
Net Income	$ 168	$ 207	$ 94	$ 213	$ 109	$ 169	$ 140	$ 241	$ 682	$ 659	$ 462
Income attributable to noncontrolling interests	1	0	1	0	1	0	1	0	2	2	2
Net Income Available to Common Stockholders	$ 167	$ 207	$ 93	$ 213	$ 108	$ 169	$ 139	$ 241	$ 680	$ 657	$ 460
Average common shares outstanding
Weighted average shares - basic (in shares)									283.0	282.2	280.0
Dilutive nonvested stock awards (in shares)									0.7	0.7	0.8
Dilutive forward equity sale contracts									0.6	0.0	0.0
Weighted average shares - diluted (in shares)									284.3	282.9	280.8
Basic net income per average common share available to common stockholders (in dollars per share)	$ 0.59	$ 0.73	$ 0.33	$ 0.75	$ 0.38	$ 0.60	$ 0.49	$ 0.86	$ 2.40	$ 2.33	$ 1.64
Diluted net income per average common share available to common stockholders (in dollars per share)	$ 0.58	$ 0.73	$ 0.33	$ 0.75	$ 0.38	$ 0.59	$ 0.49	$ 0.86	$ 2.39	$ 2.32	$ 1.64