v3.19.3.a.u2

Summary of significant accounting policies (Tables) | 12 Months Ended
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Dec. 31, 2019
Summary of significant accounting policies |
Summary of derivative instruments not designated, treatment of changes in fair value and cash settlements |
Derivative financial instrument |  | Classification of changes in fair value |  | Classification of cash settlements |
Natural gas swaps |  | Changes in fair value of derivative instrument |  | Fuel expense |
Fuel purchase agreements |  | Changes in fair value of derivative instrument |  | Fuel expense |
Interest rate swaps |  | Changes in fair value of derivative instrument |  | Interest expense |
Convertible debenture conversion option |  | Other expense (income), net |  | NA |
Foreign currency forward contract |  | Foreign exchange loss (gain) |  | Foreign exchange loss (gain) |

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- Definition Tabular disclosure of derivative instrument not designated or qualifying as hedging instrument. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CC -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109998890-113959 + Details
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