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Jointly Owned Facilities (Tables) | 12 Months Ended
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Dec. 31, 2011
Regulated Operations [Abstract] |
Company's share of the cost of utility plant in service and related accumulated depreciation for the stations | At December 31, the Company's share of the cost of utility plant in service and related accumulated depreciation for the stations was as follows:
| 2011 |  |  | 2010 |
| (In thousands)
Big Stone Station: |  |  |
Utility plant in service | $ | 63,715 |  |  | $ | 60,404 |
Less accumulated depreciation | 42,475 |  |  | 41,136 |
| $ | 21,240 |  |  | $ | 19,268 |
Coyote Station: |  |  |  |  |
Utility plant in service | $ | 131,719 |  |  | $ | 131,395 |
Less accumulated depreciation | 86,788 |  |  | 84,710 |
| $ | 44,931 |  |  | $ | 46,685 |
Wygen III:* |  |  |  |  |
Utility plant in service | $ | 63,300 |  |  | $ | 63,215 |
Less accumulated depreciation | 2,106 |  |  | 838 |
| $ | 61,194 |  |  | $ | 62,377 |
* Began commercial operation on April 1, 2010.

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- Definition Tabular disclosure of public utility property plant and equipment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph b -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499596&loc=d3e42232-110370 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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