Commitments and contingencies (Tables) |
12 Months Ended | ||||||||||||||||||||||||||||||||||||||||
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Dec. 31, 2015 | |||||||||||||||||||||||||||||||||||||||||
| Schedule of future minimum lease commitments under operating leases |
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| Maintenance Services for Turbine Equipment [Member] | |||||||||||||||||||||||||||||||||||||||||
| Schedule of estimated commitments under fuel supply and transportation agreements |
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| Fuel and Transportation Services [Member] | |||||||||||||||||||||||||||||||||||||||||
| Schedule of estimated commitments under fuel supply and transportation agreements |
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