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v2.4.0.8

Significant accounting policies - Revenue Recognition (Details) (Minimum) | 12 Months Ended
--- | ---
Dec. 31, 2013
Minimum |
Property, Plant and Equipment [Line Items] |
Term of contract (less than one year) | 1 year

X
- Definition Term of Contract + References No definition available. + Details
Name: | noa_TermOfContract
Namespace Prefix: | noa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration