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Commitments and contingencies (Details) (USD $)
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12 Months Ended | ||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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| 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 | ||
| X | ||||||||||
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- Definition
Represents the total estimated amount due relating to agreements in which the entity must commit resources to supply goods or services to one or more customers. No definition available.
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- Details
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- Definition
Represents the estimated amount due within one year of the balance sheet date relating to agreements in which the entity must commit resources to supply goods or services to one or more customers. No definition available.
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- Definition
Represents the estimated amount due within the fifth year of the balance sheet date relating to agreements in which the entity must commit resources to supply goods or services to one or more customers. No definition available.
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- Definition
Represents the estimated amount due within the fourth year of the balance sheet date relating to agreements in which the entity must commit resources to supply goods or services to one or more customers. No definition available.
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- Definition
Represents the estimated amount due within the third year of the balance sheet date relating to agreements in which the entity must commit resources to supply goods or services to one or more customers. No definition available.
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- Definition
Represents the estimated amount due within the second year of the balance sheet date relating to agreements in which the entity must commit resources to supply goods or services to one or more customers. No definition available.
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- Definition
Represents the estimated amount due after the fifth year of the balance sheet date relating to agreements in which the entity must commit resources to supply goods or services to one or more customers. No definition available.
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- Details
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- Definition
Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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- Definition
Amount of required minimum rental payments maturing in the next fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount of required minimum rental payments maturing in the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount of required minimum rental payments maturing in the forth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount of required minimum rental payments maturing in the third fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount of required minimum rental payments maturing in the second fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount of required minimum rental payments maturing after the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier. No definition available.
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- Definition
Minimum amount of purchase arrangement maturing after the fifth fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. No definition available.
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- Definition
Minimum amount of purchase arrangement maturing in the fifth fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. No definition available.
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- Definition
Minimum amount of purchase arrangement maturing in the fourth fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. No definition available.
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- Definition
Minimum amount of purchase arrangement maturing in the next fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. No definition available.
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- Definition
Minimum amount of purchase arrangement maturing in the second fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. No definition available.
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- Definition
Minimum amount of purchase arrangement maturing in the third fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. No definition available.
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- Details
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