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Earnings Per Share and Common Stock (Tables) | 3 Months Ended
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Mar. 31, 2012
Earnings Per Share and Common Stock [Abstract] |
Reconciliation of Basic and Diluted Earnings Per Share [Table Text Block] |
|  |  | 2012 |  |  |  |  |  | 2011 |  |
Reconciliation of Basic and Diluted |  |  | Dilutive |  |  |  |  |  | Dilutive |  |
Earnings Per Share | Basic |  | Securities |  | Diluted |  | Basic |  | Securities |  | Diluted
Millions Except Per Share Amounts |  |  |  |  |  |  |  |  |  |  |
For the Quarter Ended March 31, |  |  |  |  |  |  |  |  |  |  |
Net Income Attributable to ALLETE | $24.4 |  |  |  |  |  | $24.4 |  |  |  | $37.2 |  |  |  |  |  | $37.2 |
Common Shares | 36.8 |  |  | 0.1 |  |  | 36.9 |  |  | 34.6 |  |  | 0.1 |  |  | 34.7 |
Earnings Per Share | $0.66 |  |  |  |  | $0.66 |  |  |  | $1.07 |  |  |  |  |  | $1.07 |

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- Definition Tabular disclosure of the reconciliation of basic net earnings per share (or unit) to diluted earnings per share (or unit). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 260 -SubTopic 10 -Publisher FASB -Number -Article -Subparagraph -Name Accounting Standards Codification -Paragraph 1 -Section 50 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
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