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Financings And Capitalization (Issuance Of Common Stock) (Details) (CMS Energy [Member], USD $)
In Millions, except Share data, unless otherwise specified |
3 Months Ended | 30 Months Ended | ||
|---|---|---|---|---|
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Mar. 31, 2013
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Jun. 30, 2012
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Jun. 30, 2011
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Sep. 30, 2013
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CMS Energy [Member]
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||||
| Number of Shares Issued | 735,873 | 650,235 | 762,925 | 2,149,033 |
| Average Price Per Share | $ 27.18 | $ 23.07 | $ 19.66 | $ 23.27 |
| Proceeds | $ 20 | $ 15 | $ 15 | $ 50 |