Note 15 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 28, 2019	Mar. 30, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Income Tax Expense (Benefit), Total	$ 70		$ 253	$ 255	$ 736
Effective Income Tax Rate Reconciliation, Tax Settlement, Domestic, Amount		$ 600
Effective Income Tax Rate Reconciliation, Percent, Total				25.90%	25.80%
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Effective Income Tax Rate Reconciliation, Percent, Total				28.30%	28.10%
Foreign Tax Authority [Member] | Canada Revenue Agency [Member]
Effective Income Tax Rate Reconciliation, Percent, Total				26.50%	26.50%
Foreign Tax Authority [Member] | Ministry of Finance, Republic of Serbia [Member]
Effective Income Tax Rate Reconciliation, Percent, Total				15.00%	15.20%