| Note 2 - ASC 606 Revenue from Contracts with Customers - Impact of Adoption of ASC 606 (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended | |||||
|---|---|---|---|---|---|---|---|
| Jul. 01, 2018 | Jul. 01, 2018 | Jul. 02, 2017 | Jul. 01, 2018 | Jul. 02, 2017 | Jan. 01, 2018 | Dec. 31, 2017 | |
| Inventories | $ 25,214 | $ 25,214 | $ 25,214 | $ 18,949 | $ 22,363 | ||
| Unbilled contract assets | 6,808 | 6,808 | 6,808 | 3,734 | |||
| Total shareholders’ equity | 19,869 | 19,869 | 19,869 | 19,394 | 19,074 | ||
| Unbilled contract assets | 6,808 | 6,808 | 6,808 | 3,734 | |||
| Inventories | 25,214 | 25,214 | 25,214 | 18,949 | 22,363 | ||
| Total shareholders’ equity | 19,869 | 19,869 | 19,869 | 19,394 | $ 19,074 | ||
| Revenue | 44,479 | 44,479 | $ 32,995 | 81,599 | $ 66,173 | ||
| Cost of sales | 40,196 | 40,196 | 31,575 | 73,466 | 61,196 | ||
| Gross profit | 4,283 | 4,283 | 1,420 | 8,133 | 4,977 | ||
| Income tax expense | 234 | 234 | 154 | 260 | 147 | ||
| Net loss | (97) | (97) | $ (6,013) | (89) | $ (6,390) | ||
| Accounting Standards Update 2014-09 [Member] | |||||||
| Inventories | (3,414) | ||||||
| Unbilled contract assets | 3,734 | ||||||
| Total shareholders’ equity | 320 | ||||||
| Unbilled contract assets | 3,734 | ||||||
| Inventories | (3,414) | ||||||
| Total shareholders’ equity | $ 320 | ||||||
| Calculated under Revenue Guidance in Effect before Topic 606 [Member] | |||||||
| Inventories | 31,578 | 31,578 | 31,578 | ||||
| Unbilled contract assets | |||||||
| Total shareholders’ equity | 19,425 | 19,425 | 19,425 | ||||
| Unbilled contract assets | |||||||
| Inventories | 31,578 | 31,578 | 31,578 | ||||
| Total shareholders’ equity | 19,425 | 19,425 | 19,425 | ||||
| Revenue | 43,140 | 78,525 | |||||
| Cost of sales | 38,929 | 70,516 | |||||
| Gross profit | 4,211 | 8,009 | |||||
| Income tax expense | 234 | 260 | |||||
| Net loss | (169) | (213) | |||||
| Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | |||||||
| Revenue | 1,339 | 3,074 | |||||
| Cost of sales | 1,267 | 2,950 | |||||
| Gross profit | 72 | 124 | |||||
| Income tax expense | |||||||
| Net loss | 72 | 124 | |||||
| Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | |||||||
| Inventories | (6,364) | (6,364) | (6,364) | ||||
| Unbilled contract assets | 6,808 | 6,808 | 6,808 | ||||
| Total shareholders’ equity | 444 | 444 | 444 | ||||
| Unbilled contract assets | 6,808 | 6,808 | 6,808 | ||||
| Inventories | (6,364) | (6,364) | (6,364) | ||||
| Total shareholders’ equity | $ 444 | $ 444 | $ 444 | ||||