Employee Benefit Plans - Components of Net Periodic Pension Cost for Defined Benefit Pension Plan and Retirement Plan (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Retirement Benefits [Abstract]
Service cost	$ 155	$ 126	$ 466	$ 377
Interest cost	302	347	907	1,041
Expected return on plan assets	(440)	(411)	(1,321)	(1,233)
Amortization of actuarial losses	248	221	744	664
Net periodic pension cost	$ 265	$ 283	$ 796	$ 849