XML 24 R79.htm IDEA: XBRL DOCUMENT v2.4.0.6

Segment Information (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Manufacturing_Facility	Dec. 31, 2011	Dec. 31, 2010
Segment Information (Textual) [Abstract]
Manufacturing locations, Water Transmission	6
Threshold for disclosure, sales represented by individual customer		10.00%	10.00%
Percent of total net sales for single customer	12.00%
MEXICO [Member]
Segment Reporting Information [Line Items]
Property and equipment, net, located in Mexico	2.4	2.4

X

- Definition

Number of manufacturing facility locations for the Water Transmission segment.

+ References

No definition available.

+ Details

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

X

- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	nwpx_PropertyPlantAndEquipmentNetLocatedInMexico
Namespace Prefix:	nwpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

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

X

- Definition

Threshold for disclosure for sales represented by any one individual customer.

+ References

No definition available.

+ Details

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

X

- Definition

Percentage of revenue generated from a single external customer that accounts for 10 percent or more of an entity's revenues.

+ References

No definition available.

+ Details

Name:	us-gaap_EntityWideRevenueMajorCustomerPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration