XML 22 R54.htm IDEA: XBRL DOCUMENT v2.4.1.9

Significant accounting policies - Revenue Recognition (Details) (Minimum)	12 Months Ended
	Dec. 31, 2014
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