Earnings Per Share - CMS Energy (Basic And Diluted EPS Computations) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share - CMS Energy [Abstract]
Net income	$ 125	$ 68	$ 289	$ 270
Less income attributable to noncontrolling interest	1	1	1	1
Net Income Available to Common Stockholders	$ 124	$ 67	$ 288	$ 269
Weighted average shares - basic	278.2	275.4	277.4	275.1
Add dilutive non-vested stock awards	1.1	0.8	1.2	0.8
Weighted average shares - diluted	279.3	276.2	278.6	275.9
Basic	$ 0.45	$ 0.25	$ 1.04	$ 0.98
Diluted	$ 0.45	$ 0.25	$ 1.04	$ 0.98

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Nonvested equity-based payment awards that contain forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) that result in incremental common shares.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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