XML 72 R66.htm IDEA: XBRL DOCUMENT v2.4.1.9
Segment Reporting - Geographic Information of Long-Lived Assets by Regions (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Segment Reporting Information [Line Items]    
Long-lived assets $ 3,235us-gaap_NoncurrentAssets $ 3,050us-gaap_NoncurrentAssets
United States [Member]    
Segment Reporting Information [Line Items]    
Long-lived assets 3,193us-gaap_NoncurrentAssets
/ us-gaap_StatementGeographicalAxis
= country_US		 3,003us-gaap_NoncurrentAssets
/ us-gaap_StatementGeographicalAxis
= country_US
Rest of The World [Member]    
Segment Reporting Information [Line Items]    
Long-lived assets $ 42us-gaap_NoncurrentAssets
/ us-gaap_StatementGeographicalAxis
= nrthf_RestOfWorldMember		 $ 47us-gaap_NoncurrentAssets
/ us-gaap_StatementGeographicalAxis
= nrthf_RestOfWorldMember