Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 24,627	$ 13,434	$ 54,585	$ 32,688
Components of other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(629)	384	610	(823)
Amortization of defined benefit pension items:
Net actuarial loss (gain)	16	5	49	(1,461)
Prior service cost	13	12	36	36
Defined benefit pension plan adjustments	29	17	85	(1,425)
Other comprehensive income (loss), net of tax	658	(367)	(525)	(602)
Comprehensive income	$ 25,285	$ 13,067	$ 54,060	$ 32,086