XML 93 R78.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Note 16 - Accumulated Other Comprehensive Loss - Summary of Accumulated Other Comprehensive Loss (Details) (Parentheticals) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Pension liability adjustment, tax effect | $ 886 | $ 966
Net deferred gain (loss) on cash flow derivatives, tax effect | $ 6 | $ 49

X
- Definition Tax expense (benefit) included in accumulated other comprehensive income for cash flow hedges. + References No definition available. + Details
Name: | nwpx_AccumulatedOtherComprehensiveIncomeLossCumulativeChangeInNetGainLossFromCashFlowHedgeEffectTax
Namespace Prefix: | nwpx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Tax expense (benefit) included in accumulated other comprehensive income for defined benefit pension and other postretirement plans. + References No definition available. + Details
Name: | nwpx_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansTaxExpenseBenefit
Namespace Prefix: | nwpx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration