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Note 5 - Inventories (Tables) | 12 Months Ended
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Dec. 31, 2018
Notes Tables |
Schedule Of Inventory Current And Non Current [Table Text Block] |
|  | December 31, |
|  | 2018 |  |  | 2017 |
Current inventories: |  |  |  |  |  |  |  |
Raw materials |  | $ | 34,426 |  |  | $ | 13,700 |
Work-in-process |  |  | 2,368 |  |  |  | 1,268 |
Finished goods |  |  | 1,075 |  |  |  | 464 |
Supplies |  |  | 1,507 |  |  |  | 1,623 |
Total current inventories |  |  | 39,376 |  |  |  | 17,055 |
Noncurrent inventories: |  |  |  |  |  |  |  |
Finished goods |  |  | 65 |  |  |  | 820 |
Total inventories |  | $ | 39,441 |  |  | $ | 17,875 |

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- Definition Tabular disclosure of the carrying amount as of the balance sheet date of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process. Includes current and non-current inventory balances. + References No definition available. + Details
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Namespace Prefix: | nwpx_
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Balance Type: | na
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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration