Benefit Plans - Benefit Plan Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Retirement Benefits [Abstract]
Service cost	$ 592	$ 514	$ 1,210	$ 1,014
Interest cost	486	813	1,144	1,597
Expected return on plan assets	(402)	(821)	(1,129)	(1,611)
Amortization of prior service and net actuarial loss	264	62	409	124
Net periodic benefit cost	$ 940	$ 568	$ 1,634	$ 1,124