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Earnings Per Share and Common Stock (Tables) | 9 Months Ended
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Sep. 30, 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 September 30, |  |  |  |  |  |  |  |  |  |  |
Net Income Attributable to ALLETE |  | $29.4 |  |  |  |  |  | $29.4 |  |  |  | $20.5 |  |  |  |  |  | $20.5 |
Average Common Shares | 37.7 |  |  | 0.1 |  |  | 37.8 |  |  | 35.6 |  |  | 0.1 |  |  | 35.7 |
Earnings Per Share |  | $0.78 |  |  |  |  |  | $0.78 |  |  |  | $0.57 |  |  |  |  |  | $0.57 |
For the Nine Months Ended September 30, |  |  |  |  |  |  |  |  |  |  |  |  |
Net Income Attributable to ALLETE |  | $68.2 |  |  |  |  |  | $68.2 |  |  |  | $74.7 |  |  |  |  |  | $74.7 |
Average Common Shares | 37.3 |  |  | — |  |  | 37.3 |  |  | 35.1 |  |  | 0.1 |  |  | 35.2 |
Earnings Per Share |  | $1.83 |  |  |  |  |  | $1.83 |  |  |  | $2.13 |  |  |  |  |  | $2.12 |

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
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