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Intangible assets and goodwill - Schedule of Intangible Assets (Detail) - CAD CAD in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Finite-Lived Intangible Assets [Line Items] |  |
Cost | CAD 122,338 | CAD 121,186
Accumulated amortization | 58,230 | 56,197
Net book value | 64,108 | 64,989
Power sales contracts |  |
Finite-Lived Intangible Assets [Line Items] |  |
Cost | 70,929 | 72,207
Accumulated amortization | 46,263 | 44,641
Net book value | 24,666 | 27,566
Customer relationships |  |
Finite-Lived Intangible Assets [Line Items] |  |
Cost | 33,619 | 35,979
Accumulated amortization | 11,085 | 10,999
Net book value | 22,534 | 24,980
Interconnection agreements |  |
Finite-Lived Intangible Assets [Line Items] |  |
Cost | 17,790 | 13,000
Accumulated amortization | 882 | 557
Net book value | CAD 16,908 | CAD 12,443

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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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- Definition Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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