Benefit Plans - Benefit Plan Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Components of net periodic benefit cost:
Service cost	$ 2,266	$ 2,037	$ 1,509
Interest cost	3,104	1,887	1,662
Expected return on plan assets	(3,222)	(1,990)	(1,935)
Amortization of prior service	291	337	306
Net periodic benefit cost	2,439	2,271	1,542
Settlement loss / curtailment (gain)	238	(25)	(36)
Total expense for the year	$ 2,677	$ 2,246	$ 1,506