Benefit Plans - Benefit Plan Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Components of net periodic benefit cost:
Service cost	$ 2,040	$ 2,266	$ 2,037
Interest cost	3,169	3,104	1,887
Expected return on plan assets	(3,187)	(3,222)	(1,990)
Amortization of prior service and net actuarial loss	243	291	337
Net periodic benefit cost	2,265	2,439	2,271
Settlement loss / curtailment (gain)	260	238	(25)
Total expense for the year	$ 2,525	$ 2,677	$ 2,246