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Subsequent events (Details) (Subsequent event, CAD) In Thousands, unless otherwise specified | Jan. 02, 2015
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Subsequent event |
Subsequent Event [Line Items] |
Net proceeds from sale of contract-related assets | 36,347 noa_DisposalGroupIncludingDiscontinuedOperationConsideration / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember

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- Definition Disposal Group, Including Discontinued Operation, Consideration + References No definition available. + Details
Name: | noa_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix: | noa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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