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Investment in ATC (Tables) | 6 Months Ended
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Jun. 30, 2013
Investment in ATC [Abstract] |
ALLETE's Investment in ATC [Table Text Block] |
ALLETE’s Investment in ATC |
Millions |
Equity Investment Balance as of December 31, 2012 |  | $107.3 |
Cash Investments | 1.6 |
Equity in ATC Earnings | 10.2 |
Distributed ATC Earnings | (7.9 | )
Equity Investment Balance as of June 30, 2013 |  | $111.2 |
ATC Summarized Financial Data [Table Text Block] | ATC’s summarized financial data for the quarters and six months ended June 30, 2013 and 2012, is as follows:
| Quarter Ended |  | Six Months Ended
ATC Summarized Financial Data | June 30, |  | June 30,
Income Statement Data | 2013 |  | 2012 |  | 2013 |  | 2012
Millions |  |  |  |  |  |  |
Revenue |  | $152.1 |  |  | $152.2 |  |  | $303.9 |  |  |  | $299.8 |
Operating Expense | 69.9 |  |  | 71.8 |  | 139.7 |  |  | 141.3 |
Other Expense | 20.9 |  |  | 21.1 |  | 42.4 |  |  | 41.1 |
Net Income |  | $61.3 |  |  | $59.3 |  |  | $121.8 |  |  |  | $117.4 |
ALLETE’s Equity in Net Income |  | $5.0 |  |  | $4.8 |  |  | $10.2 |  |  |  | $9.4 |

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- Definition Tabular disclosure of equity method investments including, but not limited to, name of each investee or group of investments, percentage ownership, difference between recorded amount of an investment and the value of the underlying equity in the net assets, and summarized financial information. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
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