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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 64,055,000noa_CapitalLeaseObligationsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		 [1] 43,295,000noa_CapitalLeaseObligationsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		 [1]
Series 1 Debentures 58,733,000us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		 [2] 75,000,000us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		 [2]
Fair Value    
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]    
Capital lease obligations 58,951,000noa_CapitalLeaseObligationsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 [1] 39,508,000noa_CapitalLeaseObligationsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 [1]
Series 1 Debentures 58,733,000us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 [2] 77,813,000us-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 5,500,000us-gaap_LongtermDebtPercentageBearingVariableInterestAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		 0us-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 100,000noa_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.