v2.4.0.6

Commitments and contingencies (Details) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Commitments and contingencies |  |  |
Lease expense under operating leases | $ 2,000,000 | $ 1,000,000 | $ 900,000
Future minimum lease commitments under operating leases |  |  |
2013 | 1,048,000 |  |
2014 | 1,064,000 |  |
2015 | 677,000 |  |
2016 | 460,000 |  |
2017 | 451,000 |  |
Thereafter | 4,805,000 |  |
Future minimum lease commitments | 8,505,000 |  |
Estimated commitments under Transmission and Long-Term Service Agreements |  |  |
2013 | 3,178,000 |  |
2014 | 3,225,000 |  |
2015 | 4,744,000 |  |
2016 | 4,754,000 |  |
2017 | 4,615,000 |  |
Thereafter | 22,777,000 |  |
Total | 43,293,000 |  |
Fuel Supply and Transportation Commitments |  |  |
2013 | 77,329,000 |  |
2014 | 80,862,000 |  |
2015 | 80,921,000 |  |
2016 | 82,722,000 |  |
2017 | 18,249,000 |  |
Thereafter | 114,054,000 |  |
Total | $ 454,137,000 |  |

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