XML 102 R88.htm IDEA: XBRL DOCUMENT
v3.19.1

Note 20 - Quarterly Data (Unaudited) (Details Textual) - USD ($) $ in Thousands |  | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jul. 27, 2018 | Dec. 31, 2018 | Aug. 31, 2018 | Dec. 31, 2018 | Sep. 30, 2018 | Dec. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Gain (Loss) on Disposition of Property Plant Equipment, Total |  |  |  |  |  |  | $ (222) | $ 51 | $ (19)
Business Combination, Bargain Purchase, Gain Recognized, Amount |  |  |  |  | $ 21,900 |  | $ 20,080 |  |
Cost of Sales [Member] |  |  |  |  |  |  |  |  |
Workers Compensation Expense |  |  |  |  |  | $ 1,200 |  |  |
Ameron Water Transmission Group, LLC [Member] |  |  |  |  |  |  |  |  |
Business Combination, Bargain Purchase, Gain Recognized, Amount | $ 20,080 |  |  |  |  |  |  |  |
Business Combination, Bargain Purchase, Increase (Decrease) in Gain Recognized, Measurement Period Adjustment |  |  |  | $ (1,800) |  |  |  |  |
Property in Houston, Texas [Member] |  |  |  |  |  |  |  |  |
Gain (Loss) on Disposition of Property Plant Equipment, Total |  |  | $ 2,800 |  | $ 2,800 |  |  |  |
Monterrey, Mexico Facility [Member] |  |  |  |  |  |  |  |  |
Gain (Loss) on Disposition of Property Plant Equipment, Total |  | $ 200 |  | $ 200 |  |  |  |  |

X
- Definition In a business combination in which the amount of net identifiable assets acquired and liabilities assumed exceeds the aggregate consideration transferred or to be transferred (as defined) due to measurement period adjustment, this element represents the increase (decrease) amount of gain recognized by the entity. + References No definition available. + Details
Name: | nwpx_BusinessCombinationBargainPurchaseIncreaseDecreaseInGainRecognizedMeasurementPeriodAdjustment
Namespace Prefix: | nwpx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of workers compensation charge related to a change in estimate to workers compensation reserves. + References No definition available. + Details
Name: | nwpx_WorkersCompensationExpense
Namespace Prefix: | nwpx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition In a business combination in which the amount of net identifiable assets acquired and liabilities assumed exceeds the aggregate consideration transferred or to be transferred (as defined), this element represents the amount of gain recognized by the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6571-128477 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (f)(1) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6387-128476 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6396-128476 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6527-128477 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6393-128476 + Details
Name: | us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
Name: | us-gaap_GainLossOnSaleOfPropertyPlantEquipment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_CostOfSalesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=nwpx_AmeronWaterTransmissionGroupLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=nwpx_PropertyInHoustonTexasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=nwpx_MonterreyMexicoFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |