XML 102 R69.htm IDEA: XBRL DOCUMENT v2.4.1.9

Share-Based Compensation Plans - Summary of Status of Company's RSUs and PSAs (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
vesting period	60 months
Restricted Stock Units and Performance Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target level of RSUs and PSAs	100.00%nwpx_RestrictedStockUnitsAndPerformanceShareAwardTargetLevelPercentage / us-gaap_AwardTypeAxis = nwpx_RestrictedStockUnitsAndPerformanceAwardsMember
vesting period	3 years
PSAs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares vested for awards	13,161us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares / us-gaap_AwardTypeAxis = nwpx_PerformanceShareAwardsMember
vesting period	3 years
Actual payout percentage	143.00%nwpx_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantActualPayoutPercentage / us-gaap_AwardTypeAxis = nwpx_PerformanceShareAwardsMember

X

- Definition

Restricted Stock Units And Performance Share Award Target Level Percentage

+ References

No definition available.

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Shares Available For Grant Actual Payout Percentage

+ References

No definition available.

+ Details

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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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Number of options vested.

+ References

No definition available.

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