XML 60 R48.htm IDEA: XBRL DOCUMENT v3.19.3

Note 9 - Commitments and Contingencies (Details Textual) $ in Thousands	1 Months Ended	9 Months Ended
	Jan. 31, 2017 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2014 USD ($)
Number Of Potentially Responsible Parties		150
Estimated Cost of EPA Selected Remedy	$ 1,000,000
Estimated Time to Complete Selected EPA Remedy	13 years
Proceeds from Insurance Settlement, Investing Activities		$ 1,400
Gain (Loss) on Insurance Proceeds		431
Letters of Credit Outstanding, Amount		1,600
Fire [Member]
Proceeds from Insurance Settlement, Investing Activities		1,400
Gain (Loss) on Insurance Proceeds		400
Business Interruption Costs		3,900
Business Interruption Insurance Proceeds		1,000
Fire [Member] | Property, Plant and Equipment [Member]
Unusual or Infrequent Item, or Both, Net (Gain) Loss, Total		900
Fire [Member] | Inventory [Member]
Unusual or Infrequent Item, or Both, Net (Gain) Loss, Total		$ 100
Portland Harbor Natural Resources Trustee Council [Member]
Loss Contingency, Accrual, Current				$ 400
Lower Willamette Group [Member]
Number Of Potentially Responsible Parties		14

X

- Definition

Represents the amount of business interruption costs.

+ References

No definition available.

+ Details

Name:	nwpx_BusinessInterruptionCosts
Namespace Prefix:	nwpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Represents the amount of business interruption insurance proceeds received.

+ References

No definition available.

+ Details

Name:	nwpx_BusinessInterruptionInsuranceProceeds
Namespace Prefix:	nwpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The estimated cost of the remedy selected by EPA.

+ References

No definition available.

+ Details

Name:	nwpx_EstimatedCostOfEPASelectedRemedy
Namespace Prefix:	nwpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The estimated amount of time to complete the selected EPA remedy.

+ References

No definition available.

+ Details

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

X

- Definition

Amount of gain (loss) on insurance proceeds during the period.

+ References

No definition available.

+ Details

Name:	nwpx_GainLossOnInsuranceProceeds
Namespace Prefix:	nwpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Number of potentially responsible parties for Portland Harbor Superfund site.

+ References

No definition available.

+ Details

Name:	nwpx_NumberOfPotentiallyResponsibleParties
Namespace Prefix:	nwpx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount of loss contingency liability expected to be resolved within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349

+ Details

Name:	us-gaap_LossContingencyAccrualCarryingValueCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount of cash inflow for proceeds from settlement of insurance claim, classified as investing activities. Excludes insurance settlement classified as operating activities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 21B
-URI http://asc.fasb.org/extlink&oid=118932676&loc=SL94080549-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromInsuranceSettlementInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of (gain) loss for an event or transaction that is unusual in nature or occurs infrequently, or both.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=114868879&loc=SL114871939-224231

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=114868883&loc=SL114871943-224233

+ Details

Name:	us-gaap_UnusualOrInfrequentItemNetGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

Name:	us-gaap_NoncatastrophicEventAxis=us-gaap_FireMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_PropertyPlantAndEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=nwpx_InventoryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=nwpx_PortlandHarborNaturalreSourcesTrusteeCouncilMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CounterpartyNameAxis=nwpx_LowerWillametteGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: