XML 61 R72.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Commitments and Contingencies - Additional Information (Detail) (USD $) | 1 Months Ended |  | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2007 | Dec. 31, 2013 Parties | Dec. 31, 2013 Portland Harbor Natural Resources Trustee Council [Member] | Dec. 31, 2013 Minimum [Member] | Dec. 31, 2013 Maximum [Member]
Other Commitments [Line Items] |  |  |  |  |
Company made payment to Lower Willamette Group as interim settlement | $ 175,000 |  |  |  |
Liability to pay | 0 |  | 0 |  |
Estimated cost |  |  |  | 169,000,000 | 1,760,000,000
Estimated years to implement |  |  |  | 2 years | 28 years
Amount spent for Source Control work |  | 100,000 |  |  |
Amount anticipated to spent for further Source Control work |  | 100,000 |  |  |
Cost of remedy expected to be allocated among potentially responsible parties |  | 100 |  |  |
Total stand-by letters of credit |  | $ 3,100,000 |  |  |

X
- Definition Amount anticipated to spent for further source control work during the upcoming fiscal year. + References No definition available. + Details
Name: | nwpx_AmountAnticipatedToSpentForFurtherSourceControlWork
Namespace Prefix: | nwpx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount spent to complete work specified in work plans. + References No definition available. + Details
Name: | nwpx_AmountSpentToCompleteWorkSpecifiedInWorkPlans
Namespace Prefix: | nwpx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Cost Of Remedy Expected To Be Allocated Among Potentially Responsible Parties + References No definition available. + Details
Name: | nwpx_CostOfRemedyExpectedToBeAllocatedAmongPotentiallyResponsibleParties
Namespace Prefix: | nwpx_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Estimated cost of EPA selected remedy. + References No definition available. + Details
Name: | nwpx_EstimatedCostOfEpaSelectedRemedy
Namespace Prefix: | nwpx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Estimated time to complete 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 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 Aggregate carrying amount of the estimated litigation liability for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.25) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LitigationReserve
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of judgment or settlement awarded to (against) the entity in respect of litigation. + References No definition available. + Details
Name: | us-gaap_LitigationSettlementAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_OtherCommitmentsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration