<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.24.1.u1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>169</ContextCount>
  <ElementCount>208</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>43</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-document-and-entity-information</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-condensed-consolidated-statements-of-operations-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-condensed-consolidated-statements-of-comprehensive-income-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Current Period Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited-parentheticals</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-condensed-consolidated-statements-of-stockholders-equity-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-condensed-consolidated-statements-of-stockholders-equity-unaudited-parentheticals</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-condensed-consolidated-statements-of-cash-flows-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Disclosure - Note 1 - Organization and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-1-organization-and-basis-of-presentation</Role>
      <ShortName>Note 1 - Organization and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Note 2 - Inventories</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-2-inventories</Role>
      <ShortName>Note 2 - Inventories</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Note 3 - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-3-fair-value-measurements</Role>
      <ShortName>Note 3 - Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Note 4 - Derivative Instruments and Hedging Activities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-4-derivative-instruments-and-hedging-activities</Role>
      <ShortName>Note 4 - Derivative Instruments and Hedging Activities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Note 5 - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-5-stockholders-equity</Role>
      <ShortName>Note 5 - Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Note 6 - Share-based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-6-sharebased-compensation</Role>
      <ShortName>Note 6 - Share-based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Note 7 - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-7-commitments-and-contingencies</Role>
      <ShortName>Note 7 - Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Note 8 - Revenue</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-8-revenue</Role>
      <ShortName>Note 8 - Revenue</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Note 9 - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-9-income-taxes</Role>
      <ShortName>Note 9 - Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Note 10 - Accumulated Other Comprehensive Loss</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-10-accumulated-other-comprehensive-loss</Role>
      <ShortName>Note 10 - Accumulated Other Comprehensive Loss</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Note 11 - Net Income Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-11-net-income-per-share</Role>
      <ShortName>Note 11 - Net Income Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Note 12 - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-12-segment-information</Role>
      <ShortName>Note 12 - Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>020 - Disclosure - Note 13 - Recent Accounting and Reporting Developments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-13-recent-accounting-and-reporting-developments</Role>
      <ShortName>Note 13 - Recent Accounting and Reporting Developments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995467 - Disclosure - Note 2 - Inventories (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-2-inventories-tables</Role>
      <ShortName>Note 2 - Inventories (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-2-inventories</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995468 - Disclosure - Note 3 - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-3-fair-value-measurements-tables</Role>
      <ShortName>Note 3 - Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-3-fair-value-measurements</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995469 - Disclosure - Note 4 - Derivative Instruments and Hedging Activities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-4-derivative-instruments-and-hedging-activities-tables</Role>
      <ShortName>Note 4 - Derivative Instruments and Hedging Activities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-4-derivative-instruments-and-hedging-activities</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995470 - Disclosure - Note 6 - Share-based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-6-sharebased-compensation-tables</Role>
      <ShortName>Note 6 - Share-based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-6-sharebased-compensation</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995471 - Disclosure - Note 8 - Revenue (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-8-revenue-tables</Role>
      <ShortName>Note 8 - Revenue (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-8-revenue</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995472 - Disclosure - Note 10 - Accumulated Other Comprehensive Loss (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-10-accumulated-other-comprehensive-loss-tables</Role>
      <ShortName>Note 10 - Accumulated Other Comprehensive Loss (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-10-accumulated-other-comprehensive-loss</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995473 - Disclosure - Note 11 - Net Income Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-11-net-income-per-share-tables</Role>
      <ShortName>Note 11 - Net Income Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-11-net-income-per-share</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995474 - Disclosure - Note 12 - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-12-segment-information-tables</Role>
      <ShortName>Note 12 - Segment Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-12-segment-information</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995475 - Disclosure - Note 1 - Organization and Basis of Presentation (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-1-organization-and-basis-of-presentation-details-textual</Role>
      <ShortName>Note 1 - Organization and Basis of Presentation (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-1-organization-and-basis-of-presentation</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995476 - Disclosure - Note 2 - Inventories - Components of Inventories (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-2-inventories-components-of-inventories-details</Role>
      <ShortName>Note 2 - Inventories - Components of Inventories (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995477 - Disclosure - Note 3 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-3-fair-value-measurements-assets-and-liabilities-measured-at-fair-value-on-recurring-basis-details</Role>
      <ShortName>Note 3 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995478 - Disclosure - Note 4 - Derivative Instruments and Hedging Activities (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-4-derivative-instruments-and-hedging-activities-details-textual</Role>
      <ShortName>Note 4 - Derivative Instruments and Hedging Activities (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-4-derivative-instruments-and-hedging-activities-tables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995479 - Disclosure - Note 4 - Derivative Instruments and Hedging Activities - Summary of Gains (Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-4-derivative-instruments-and-hedging-activities-summary-of-gains-losses-details</Role>
      <ShortName>Note 4 - Derivative Instruments and Hedging Activities - Summary of Gains (Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995480 - Disclosure - Note 5 - Stockholders' Equity (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-5-stockholders-equity-details-textual</Role>
      <ShortName>Note 5 - Stockholders' Equity (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-5-stockholders-equity</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995481 - Disclosure - Note 6 - Share-based Compensation (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-6-sharebased-compensation-details-textual</Role>
      <ShortName>Note 6 - Share-based Compensation (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-6-sharebased-compensation-tables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995482 - Disclosure - Note 6 - Share-based Compensation - Share-based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-6-sharebased-compensation-sharebased-compensation-expense-details</Role>
      <ShortName>Note 6 - Share-based Compensation - Share-based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995483 - Disclosure - Note 6 - Share-based Compensation - RSU and PSA Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-6-sharebased-compensation-rsu-and-psa-activity-details</Role>
      <ShortName>Note 6 - Share-based Compensation - RSU and PSA Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995484 - Disclosure - Note 7 - Commitments and Contingencies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-7-commitments-and-contingencies-details-textual</Role>
      <ShortName>Note 7 - Commitments and Contingencies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-7-commitments-and-contingencies</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995485 - Disclosure - Note 8 - Revenue 1 (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-8-revenue-1-details-textual</Role>
      <ShortName>Note 8 - Revenue 1 (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-8-revenue-tables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995486 - Disclosure - Note 8 - Revenue 2 (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-8-revenue-2-details-textual</Role>
      <ShortName>Note 8 - Revenue 2 (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-8-revenue-tables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995487 - Disclosure - Note 8 - Revenue - Disaggregation of Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-8-revenue-disaggregation-of-revenue-details</Role>
      <ShortName>Note 8 - Revenue - Disaggregation of Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995488 - Disclosure - Note 8 - Revenue - Contract With Customer Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-8-revenue-contract-with-customer-assets-and-liabilities-details</Role>
      <ShortName>Note 8 - Revenue - Contract With Customer Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995489 - Disclosure - Note 9 - Income Taxes (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-9-income-taxes-details-textual</Role>
      <ShortName>Note 9 - Income Taxes (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-9-income-taxes</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995490 - Disclosure - Note 10 - Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-10-accumulated-other-comprehensive-loss-components-of-accumulated-other-comprehensive-loss-details</Role>
      <ShortName>Note 10 - Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>995491 - Disclosure - Note 10 - Accumulated Other Comprehensive Loss - Reclassification of Accumulated Other Comprehensive Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-10-accumulated-other-comprehensive-loss-reclassification-of-accumulated-other-comprehensive-loss-details</Role>
      <ShortName>Note 10 - Accumulated Other Comprehensive Loss - Reclassification of Accumulated Other Comprehensive Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>995492 - Disclosure - Note 11 - Net Income Per Share (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-11-net-income-per-share-details-textual</Role>
      <ShortName>Note 11 - Net Income Per Share (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nwpipe.com/20240331/role/statement-note-11-net-income-per-share-tables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>995493 - Disclosure - Note 11 - Net Income Per Share - Loss Per Basic and Diluted Weighted Average Common Share Outstanding for Continuing and Discontinued Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-11-net-income-per-share-loss-per-basic-and-diluted-weighted-average-common-share-outstanding-for-continuing-and-discontinued-operations-details</Role>
      <ShortName>Note 11 - Net Income Per Share - Loss Per Basic and Diluted Weighted Average Common Share Outstanding for Continuing and Discontinued Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="nwpx20240331_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>995494 - Disclosure - Note 12 - Segment Information - Information Related to the Operations of the Company's Operating Segments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nwpipe.com/20240331/role/statement-note-12-segment-information-information-related-to-the-operations-of-the-companys-operating-segments-details</Role>
      <ShortName>Note 12 - Segment Information - Information Related to the Operations of the Company's Operating Segments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 44 fact(s) appearing in ix:hidden were eligible for transformation: dei:EntityRegistrantName, ecd:NonRule10b51ArrAdoptedFlag, ecd:NonRule10b51ArrTrmntdFlag, ecd:Rule10b51ArrAdoptedFlag, ecd:Rule10b51ArrTrmntdFlag, nwpx:NumberOfInactiveStockIncentivePlans, us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment, us-gaap:AllowanceForDoubtfulAccountsReceivable, us-gaap:CommonStockParOrStatedValuePerShare, us-gaap:CommonStockSharesAuthorized, us-gaap:CommonStockSharesIssued, us-gaap:CommonStockSharesOutstanding, us-gaap:DerivativeNotionalAmount, us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTaxParent, us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax, us-gaap:PreferredStockParOrStatedValuePerShare, us-gaap:PreferredStockSharesAuthorized, us-gaap:PreferredStockSharesIssued, us-gaap:PreferredStockSharesOutstanding, us-gaap:RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1, us-gaap:RevenueRemainingPerformanceObligationPercentage -  nwpx20240331_10q.htm 8, 13, 14, 15, 16, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 56, 57, 58</Log>
  </Logs>
  <InputFiles>
    <File>nwpx-20240331.xsd</File>
    <File>nwpx-20240331_cal.xml</File>
    <File>nwpx-20240331_def.xml</File>
    <File>nwpx-20240331_lab.xml</File>
    <File>nwpx-20240331_pre.xml</File>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="nwpx20240331_10q.htm">nwpx20240331_10q.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2024</BaseTaxonomy>
    <BaseTaxonomy items="504">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="5">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
