Commitments and contingencies (Tables) |
12 Months Ended | ||||||||||||||||||||||||||||||||||||||||
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Dec. 31, 2019 | |||||||||||||||||||||||||||||||||||||||||
| Management Service Commitments | |||||||||||||||||||||||||||||||||||||||||
| Schedule of estimated commitments under fuel supply and transportation agreements |
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| Fuel Supply and Transportation Commitments | |||||||||||||||||||||||||||||||||||||||||
| Schedule of estimated commitments under fuel supply and transportation agreements |
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