Lease Commitments - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Leases [Abstract]
Short-term lease expenses	$ 117	$ 153
Variable lease expenses	318	194
Operating lease rent expenses	2,173	2,193
Total operating lease costs	$ 2,608	$ 2,540