Benefit Plans - Benefit Plan Expenses (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	$ 615	$ 509	$ 1,825	$ 1,523
Interest cost	511	777	1,655	2,374
Expected return on plan assets	(422)	(773)	(1,551)	(2,384)
Amortization of prior service and net actuarial loss	279	60	688	184
Net periodic benefit cost	$ 983	$ 573	$ 2,617	$ 1,697