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Financial instruments and risk management - Financial instruments (Details) (CAD) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013
Carrying Amount |  |  |  |
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] |  |  |  |
Capital lease obligations | 64,055,000 noa_CapitalLeaseObligationsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | [1] | 43,295,000 noa_CapitalLeaseObligationsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | [1]
Series 1 Debentures | 58,733,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | [2] | 75,000,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | [2]
Fair Value |  |  |  |
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] |  |  |  |
Capital lease obligations | 58,951,000 noa_CapitalLeaseObligationsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | [1] | 39,508,000 noa_CapitalLeaseObligationsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | [1]
Series 1 Debentures | 58,733,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | [2] | 77,813,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | [2]
Credit facilities |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Outstanding balance, long-term debt | 5,500,000 us-gaap_LongtermDebtPercentageBearingVariableInterestAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_LineOfCreditMember |  | 0 us-gaap_LongtermDebtPercentageBearingVariableInterestAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_LineOfCreditMember |
Change in basis spread on variable rate | 100.00%noa_DebtInstrumentBasisSpreadonVariableRateAdjustment / us-gaap_LongtermDebtTypeAxis = us-gaap_LineOfCreditMember |  |  |
Change in annual interest expense due to interest rate change | 100,000 noa_InterestExpenseAdjustmentduetoInterestRateChange / us-gaap_LongtermDebtTypeAxis = us-gaap_LineOfCreditMember |  |  |
[1] | The fair values of amounts due under capital leases are based on management estimates which are determined by discounting cash flows required under the instruments at the interest rates currently estimated to be available for instruments with similar terms.
[2] | The fair value of the Series 1 Debentures is based upon the expected discounted cash flows and the period end market price of similar financial instruments.

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- Definition Capital Lease Obligations, Fair Value Disclosure + References No definition available. + Details
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- Definition Debt Instrument, Basis Spread on Variable Rate, Adjustment + References No definition available. + Details
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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13476-108611 + Details
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