Note 11 - Leases - Lease Expense (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 27, 2021	Mar. 28, 2020
Operating leases	[1]	$ 2,040	$ 2,151
Variable lease expense		552	532
Short-term operating leases		33	19
Amortization of leased assets		21	20
Interest on lease liabilities		0	28
Sublease income		(19)	(32)
Net lease cost		$ 2,627	$ 2,718

[1] Operating lease cost excludes impairment expense of $0.2 million related to the write-down of the Fontana facility right-of-use asset recognized in 2019.