Accounts Receivable and Contract Assets, Net (Details) - USD ($) $ in Thousands	Sep. 27, 2019	Dec. 28, 2018
Accounts Receivable And Contract Assets Net Current [Abstract]
Accounts receivable	$ 41,208	$ 35,794
Contract assets	17,392	20,454
Allowance for doubtful accounts	(710)	(1,441)
Accounts receivable and contract assets, net	$ 57,890	$ 54,807