XML 76 R56.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Significant accounting policies - Property, plant and equipment (Details) | 12 Months Ended
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Dec. 31, 2017
Heavy equipment | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 5000 hours
Heavy equipment | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 70000 hours
Major component parts in use | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 1000 hours
Major component parts in use | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 36000 hours
Other equipment | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 5 years
Other equipment | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 10 years
Licensed motor vehicles | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 5 years
Licensed motor vehicles | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 10 years
Office and computer equipment |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 4 years
Buildings | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 10 years
Buildings | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 25 years

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Details
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Data Type: | na
Balance Type: |
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- Details
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Data Type: | na
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- Details
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Data Type: | na
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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=noa_MajorComponentPartsInUseMember
Namespace Prefix: |
Data Type: | na
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_VehiclesMember
Namespace Prefix: |
Data Type: | na
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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=noa_OfficeAndComputerEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
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