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Property, plant and equipment - Additional Information (Detail) - CAD CAD in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Property, Plant, and Equipment Disclosure [Line Items] |  |
Contribution received | CAD 16,044 | CAD 49,794
Water & wastewater |  |
Property, Plant, and Equipment Disclosure [Line Items] |  |
Expansion costs | 1,000 |
St Damase Wind Facility |  |
Property, Plant, and Equipment Disclosure [Line Items] |  |
Contribution received |  | 14
Generation |  |
Property, Plant, and Equipment Disclosure [Line Items] |  |
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE | 142,789 | 142,246
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE, accumulated depreciation | 43,792 | 39,958
Depreciation expense | 2,117 | CAD 2,117
Distribution |  |
Property, Plant, and Equipment Disclosure [Line Items] |  |
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE | 2,234,243 |
Renewable generation assets related to facilities under capital lease and owned by consolidated VIE, accumulated depreciation | CAD 587,202 |

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- Definition Capital Leased Assets and Plant Property and Equipment Owned by Consolidated VIE, Accumulated Depreciation + References No definition available. + Details
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- Definition Capital Leased Assets and Plant Property and Equipment Owned by Consolidated VIE, Gross + References No definition available. + Details
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- Definition Expansion Costs for Plant Not Currently Earning Return + References No definition available. + Details
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- Definition Property, Plant, and Equipment Disclosure [Line Items] + References No definition available. + Details
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- Definition The charge for the use of long-lived depreciable capital leased assets for the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 840 -Section 55 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=84167768&loc=d3e56872-110439 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84164758&loc=d3e45031-112735 + Details
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- Details
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