Net Periodic Benefit Expense - Defined Benefit Pension Plans (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020 USD ($)	Jun. 29, 2019 USD ($)	Jun. 27, 2020 USD ($)	Jun. 29, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, number of employees settled			231
Pension plans, defined benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service costs--increase in benefit obligation earned	$ 0	$ 30	$ 0	$ 75
Interest cost on projected benefit obligation	27	61	53	136
Expected return on plan assets	0	(14)	0	(37)
Settlement loss	0	1,677	0	1,677
Amortization of net actuarial loss	22	31	44	75
Amortization of prior service cost	16	16	32	32
Net pension expense of defined benefit pension plans	$ 65	$ 1,801	$ 129	$ 1,958