XML 78 R59.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Significant accounting policies - Stock-based compensation (Details) | 12 Months Ended
--- | ---
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Number of trading days used to determine weighted average trading price of common shares | 30 days
Restricted Share Unit (RSU) |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Award service period | 2 years
Award vesting period | 3 years
Compensation expense recognition period | 3 years
Phantom Share Units (PSUs) |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Award vesting period | 3 years
Compensation expense recognition period | 3 years

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Number of Trading Days Used to Calculate Weighted Average Trading Price of Common Stock + References No definition available. + Details
Name: | noa_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfTradingDaysUsedToCalculateWeightedAverageTradingPriceOfCommonStock
Namespace Prefix: | noa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Period for Recognition + References No definition available. + Details
Name: | noa_ShareBasedCompensationArrangementByShareBasedPaymentAwardPeriodForRecognition
Namespace Prefix: | noa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_PhantomShareUnitsPSUsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |