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Plant and equipment (Details) - CAD CAD in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Property, Plant and Equipment [Line Items] |  |
Cost | CAD 317,329 | CAD 331,352
Accumulated depreciation | 164,352 | 153,985
Net book value | 152,977 | 177,367
Assets under capital lease, cost | 143,983 | 115,798
Assets under capital lease, accumulated depreciation | 40,508 | 34,413
Assets under capital lease, net book value | 103,475 | 81,385
Total plant and equipment, cost | 461,312 | 447,150
Total accumulated depreciation | 204,860 | 188,398
Total plant and equipment, net book value | 256,452 | 258,752
Addition of plant and equipment by means of capital leases | 23,490 | 20,058
Heavy equipment |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 139,844 | 144,754
Accumulated depreciation | 51,358 | 46,292
Net book value | 88,486 | 98,462
Major component parts in use |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 115,111 | 117,042
Accumulated depreciation | 66,905 | 61,464
Net book value | 48,206 | 55,578
Other equipment |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 29,729 | 39,727
Accumulated depreciation | 16,232 | 19,580
Net book value | 13,497 | 20,147
Licensed motor vehicles |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 20,353 | 17,362
Accumulated depreciation | 18,258 | 15,388
Net book value | 2,095 | 1,974
Office and computer equipment |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 9,769 | 9,743
Accumulated depreciation | 9,112 | 8,643
Net book value | 657 | 1,100
Buildings |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 2,523 | 2,724
Accumulated depreciation | 2,487 | 2,618
Net book value | 36 | 106
Assets held under capital leases |  |
Property, Plant and Equipment [Line Items] |  |
Depreciation expense | 18,536 | 14,027
Heavy equipment |  |
Property, Plant and Equipment [Line Items] |  |
Assets under capital lease, cost | 133,468 | 105,580
Assets under capital lease, accumulated depreciation | 38,978 | 29,738
Assets under capital lease, net book value | 94,490 | 75,842
Other equipment |  |
Property, Plant and Equipment [Line Items] |  |
Assets under capital lease, cost | 7,119 | 1,851
Assets under capital lease, accumulated depreciation | 714 | 484
Assets under capital lease, net book value | 6,405 | 1,367
Licensed motor vehicles |  |
Property, Plant and Equipment [Line Items] |  |
Assets under capital lease, cost | 3,373 | 8,344
Assets under capital lease, accumulated depreciation | 805 | 4,186
Assets under capital lease, net book value | 2,568 | 4,158
Office and computer equipment |  |
Property, Plant and Equipment [Line Items] |  |
Assets under capital lease, cost | 23 | 23
Assets under capital lease, accumulated depreciation | 11 | 5
Assets under capital lease, net book value | CAD 12 | CAD 18

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- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land or leased assets). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The increase during the period in capital lease obligations due to entering into new capital leases. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 + Details
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- Definition Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6455314&loc=d3e45014-112735 + Details
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- Definition The total gross amount less the charge for the use of the long-lived depreciable assets subject to a lease meeting the criteria for capitalization. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737 + Details
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- Definition The total charge for the use of long-lived depreciable assets subject to a lease meeting the criteria for capitalization. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6455314&loc=d3e45014-112735 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 2) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 + Details
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- Definition The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
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- Definition Gross amount of long-lived physical assets excluding assets held under lease agreements used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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