XML 56 R41.htm IDEA: XBRL DOCUMENT v2.4.0.6

Share-based Compensation (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013 OptionPlan	Dec. 31, 2012
Share-Based Compensation (Additional Textual) [Abstract]
Number of Inactive Stock Option plans	1
Number of active stock incentive plans	1
Unrecognized compensation expense	$ 2.5
Expected period of compensation expense recognized	1 year 4 months 24 days
Maximum duration over which RSUs and PSAs become exercisable under the plan	3 years
Restricted stock units and performance awards at target level of performance included in unvested balance		115,000
Minimum Performance Awards issued multiplier		0.00%
Maximum Performance Awards issued multiplier		200.00%
Maximum [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting period of PSAs	3 years
Minimum [Member]
Share-Based Compensation (Textual) [Abstract]
Vesting period of PSAs	2 years

X

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans.

+ References

No definition available.

+ Details

Name:	nwpx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognitionInYears
Namespace Prefix:	nwpx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Maximum performance awards issued multiplier.

+ References

No definition available.

+ Details

Name:	nwpx_MaximumPerformanceAwardsIssuedMultiplier
Namespace Prefix:	nwpx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Minimum performance awards issued multiplier.

+ References

No definition available.

+ Details

Name:	nwpx_MinimumPerformanceAwardsIssuedMultiplier
Namespace Prefix:	nwpx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of active stock incentive plans.

+ References

No definition available.

+ Details

Name:	nwpx_NumberOfActiveStockIncentivePlans
Namespace Prefix:	nwpx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of inactive stock option plans.

+ References

No definition available.

+ Details

Name:	nwpx_NumberOfInactiveStockOptionPlans
Namespace Prefix:	nwpx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	nwpx_ShareBasedCompensationAdditionalTextualAbstract
Namespace Prefix:	nwpx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of non-vested equity-based payment instruments at a target level of performance, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	nwpx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberAtTargetLevelOfPerformance
Namespace Prefix:	nwpx_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Period over which an employee's right to exercise a RSU is no longer contingent on satisfaction, in years.

+ References

No definition available.

+ Details

Name:	nwpx_ShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockUnitsVestingPeriod
Namespace Prefix:	nwpx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	nwpx_ShareBasedCompensationTextualAbstract
Namespace Prefix:	nwpx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Aggregate unrecognized cost of share-based awards, other than options, made to employees under an equity-based compensation plan, that have yet to vest.

+ References

No definition available.

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration