Earnings Per Share - CMS Energy (Basic And Diluted EPS Computations) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share - CMS Energy [Abstract]
Income From continuing operations	$ 84	$ 81	$ 288	$ 225
Less income attributable to noncontrolling interest	1	1	1	1
Income from continuing operations available to common stockholders - basic and diluted	$ 83	$ 80	$ 287	$ 224
Weighted average shares - basic	268.0	264.5	267.1	264.1
Add dilutive contingently convertible securities	6.0	6.4	6.2	6.2
Add dilutive non-vested stock awards and options	0.6	1.3	0.6	1.2
Weighted average shares - diluted	274.6	272.2	273.9	271.5
Basic	$ 0.31	$ 0.30	$ 1.07	$ 0.85
Diluted	$ 0.30	$ 0.29	$ 1.05	$ 0.83

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Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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Amount of income (loss) from continuing operations attributable to the noncontrolling interest. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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

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The amount of net income (loss) derived from continuing operations during 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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