Earnings Per Share - CMS Energy (Basic And Diluted EPS Computations) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share - CMS Energy [Abstract]
Income From continuing operations	$ 102		$ 127		$ 81		$ 144		$ 67		$ 149		$ 101		$ 60		$ 454	$ 377	$ 415
Less income attributable to noncontrolling interest																	2	2	2
Income from continuing operations available to common stockholders - basic and diluted																	$ 452	$ 375	$ 413
Weighted average shares - basic																	264.5	260.7	250.8
Add dilutive contingently convertible securities																	6.4	6.8	12.2
Add dilutive non-vested stock awards and options																	1.0	1.1	0.4
Weighted average shares - diluted																	271.9	268.6	263.4
Basic	$ 0.38	[1]	$ 0.48	[1]	$ 0.30	[1]	$ 0.55	[1]	$ 0.26	[1]	$ 0.56	[1]	$ 0.38	[1]	$ 0.23	[1]	$ 1.71	$ 1.43	$ 1.65
Diluted	$ 0.37	[1]	$ 0.46	[1]	$ 0.29	[1]	$ 0.53	[1]	$ 0.25	[1]	$ 0.55	[1]	$ 0.37	[1]	$ 0.22	[1]	$ 1.66	$ 1.39	$ 1.57

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