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Significant accounting policies (Tables) | 12 Months Ended
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Dec. 31, 2017
Accounting Policies [Abstract] |
Schedule of 100% owned subsidiaries of NACHI | These consolidated financial statements include the accounts of the Company, its wholly-owned, Canadian incorporated subsidiaries, NACGI, North American Fleet Company Ltd., North American Construction Holdings Inc. (“NACHI”) and NACG Properties Inc., and the following 100% owned, Canadian incorporated subsidiaries of NACHI as of December 31, 2017:
• North American Engineering Inc. |  | • North American Site Development Ltd.
• North American Enterprises Ltd. |  | • North American Maintenance Ltd.
• North American Mining Inc. |  | • North American Tailings and Environmental Ltd.
• North American Services Inc. |  | • 1753514 Alberta Ltd.
Schedule of depreciation of property, plant and equipment | Depreciation is calculated based on the cost, net of the estimated residual value, over the estimated useful life of the assets on the following bases and rates:
Assets |  | Basis |  | Rate
Heavy equipment |  | Units of production |  | 5,000 - 70,000 hours
Major component parts in use |  | Units of production |  | 1,000 - 36,000 hours
Other equipment |  | Straight-line |  | 5 – 10 years
Licensed motor vehicles |  | Straight-line |  | 5 – 10 years
Office and computer equipment |  | Straight-line |  | 4 years
Buildings |  | Straight-line |  | 10 – 25 years
Leasehold improvements |  | Straight-line |  | Over shorter of estimated useful life and lease term
December 31, 2017 |  | Cost |  |  | Accumulated Depreciation |  |  | Net Book Value |
Owned assets |  |  |  |  |  |
Heavy equipment |  | $ | 196,045 |  |  | $ | 77,726 |  |  | $ | 118,319 |
Major component parts in use |  | 72,448 |  |  | 45,694 |  |  | 26,754 |
Other equipment |  | 31,923 |  |  | 18,400 |  |  | 13,523 |
Licensed motor vehicles |  | 18,298 |  |  | 14,888 |  |  | 3,410 |
Office and computer equipment |  | 10,157 |  |  | 9,468 |  |  | 689 |
Land |  | 7,168 |  |  | — |  |  | 7,168 |
Buildings |  | 2,547 |  |  | 2,482 |  |  | 65 |
|  | 338,586 |  |  | 168,658 |  |  | 169,928 |
Assets under capital lease |  |  |  |  |  |
Heavy equipment |  | 69,657 |  |  | 28,613 |  |  | 41,044 |
Major component parts in use |  | 85,015 |  |  | 21,247 |  |  | 63,768 |
Other equipment |  | 558 |  |  | 543 |  |  | 15 |
Licensed motor vehicles |  | 5,129 |  |  | 1,242 |  |  | 3,887 |
Office and computer equipment |  | 23 |  |  | 17 |  |  | 6 |
|  | 160,382 |  |  | 51,662 |  |  | 108,720 |
Total property, plant and equipment |  | $ | 498,968 |  |  | $ | 220,320 |  |  | $ | 278,648 |
December 31, 2016 |  | Cost |  |  | Accumulated Depreciation |  |  | Net Book Value |
Owned assets |  |  |  |  |  |
Heavy equipment |  | $ | 188,785 |  |  | $ | 68,487 |  |  | $ | 120,298 |
Major component parts in use |  | 64,229 |  |  | 49,673 |  |  | 14,556 |
Other equipment |  | 31,670 |  |  | 16,335 |  |  | 15,335 |
Licensed motor vehicles |  | 20,353 |  |  | 18,258 |  |  | 2,095 |
Office and computer equipment |  | 9,769 |  |  | 9,112 |  |  | 657 |
Buildings |  | 2,523 |  |  | 2,487 |  |  | 36 |
|  | 317,329 |  |  | 164,352 |  |  | 152,977 |
Assets under capital lease |  |  |  |  |  |
Heavy equipment |  | 84,527 |  |  | 21,848 |  |  | 62,679 |
Major component parts in use |  | 50,882 |  |  | 17,233 |  |  | 33,649 |
Other equipment |  | 5,178 |  |  | 611 |  |  | 4,567 |
Licensed motor vehicles |  | 3,373 |  |  | 805 |  |  | 2,568 |
Office and computer equipment |  | 23 |  |  | 11 |  |  | 12 |
|  | 143,983 |  |  | 40,508 |  |  | 103,475 |
Total property, plant and equipment |  | $ | 461,312 |  |  | $ | 204,860 |  |  | $ | 256,452 |

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- Definition Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -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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