XML 59 R44.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Schedule II - Valuation and Qualifying Accounts (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Notes Tables |
Summary of Valuation and Qualifying Accounts [Table Text Block] |
|  | Balance at Beginning of Perio d |  |  | Charged to Profit and Los s |  |  | Deduction from Reserve s |  |  | Balance at End of Perio d |
Year Ended December 31, 2017 : |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allowance for doubtful account s |  | $ | 515 |  |  | $ | 637 |  |  | $ | (675 | ) |  | $ | 477 |
Valuation allowance for deferred tax asset s |  |  | 8,217 |  |  |  | 2,196 |  |  |  | - |  |  |  | 10,413 |
Year Ended December 31, 2016 : |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allowance for doubtful account s |  | $ | 751 | (1) |  | $ | 295 |  |  | $ | (531 | ) |  | $ | 515 |
Valuation allowance for deferred tax asset s |  |  | 7,057 |  |  |  | 1,160 |  |  |  | - |  |  |  | 8,217 |
Year Ended December 31, 2015 : |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allowance for doubtful account s |  | $ | 755 | (1) |  | $ | 416 |  |  | $ | (420 | ) |  | $ | 751 | (1)
Valuation allowance for deferred tax asset s |  |  | 1,858 |  |  |  | 5,217 |  |  |  | (18 | ) |  |  | 7,057 |

X
- Definition A schedule of allowance and reserve accounts including their beginning and ending balances, as well as a reconciliation by type of activity during the period. Alternatively, disclosure of the required information may be within the footnotes to the financial statements or a supplemental schedule to the financial statements. + References No definition available. + Details
Name: | nwpx_SummaryOfValuationAndQualifyingAccountsTableTextBlock
Namespace Prefix: | nwpx_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_TableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration