XML 19 R50.htm IDEA: XBRL DOCUMENT v3.3.0.814

Note 15 - Related Party Transaction (Details Textual) - Eagle Asset Management [Member]	9 Months Ended
	Sep. 30, 2015 USD ($)
Related Party Transaction, Amounts of Transaction	$ 17,000
Payment of Related Party Expense	$ 12,000

X

- Definition

The cash outflow for the payment of expense from a related party.

+ References

No definition available.

+ Details

Name:	nwpx_PaymentOfRelatedPartyExpense
Namespace Prefix:	nwpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of transactions with related party during the financial reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef



-Publisher FASB



-Name Accounting Standards Codification



-Topic 850



-SubTopic 10



-Section 50



-Paragraph 3



-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864



Reference 2: http://www.xbrl.org/2003/role/presentationRef



-Publisher FASB



-Name Accounting Standards Codification



-Topic 850



-SubTopic 10



-Section 50



-Paragraph 1



-Subparagraph (c)



-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864



Reference 3: http://www.xbrl.org/2003/role/presentationRef



-Publisher FASB



-Name Accounting Standards Codification



-Topic 850



-SubTopic 10



-Section 50



-Paragraph 4



-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

+ Details

Name:	us-gaap_RelatedPartyTransactionAmountsOfTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=nwpx_EagleAssetManagementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: