Earnings Per Share - CMS Energy (Basic And Diluted EPS Computations) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share - CMS Energy [Abstract]
Net income	$ 186	$ 148	$ 475	$ 418
Less income attributable to noncontrolling interest			1	1
Net Income Available to Common Stockholders	$ 186	$ 148	$ 474	$ 417
Weighted average shares - basic	278.2	276.0	277.7	275.4
Add dilutive non-vested stock awards	1.0	0.9	1.1	0.9
Weighted average shares - diluted	279.2	276.9	278.8	276.3
Basic	$ 0.67	$ 0.53	$ 1.71	$ 1.51
Diluted	$ 0.67	$ 0.53	$ 1.70	$ 1.51