Net Periodic Benefit Expense - Defined Benefit Pension Plans (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020 USD ($)	Sep. 28, 2019 USD ($)	Sep. 26, 2020 USD ($)	Sep. 28, 2019 USD ($)
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	$ 0	$ 0	$ 75
Interest cost on projected benefit obligation	26	31	79	167
Expected return on plan assets	0	0	0	(37)
Settlement loss	0	0	0	1,677
Amortization of net actuarial loss	22	6	66	81
Amortization of prior service cost	16	16	48	48
Net pension expense of defined benefit pension plans	$ 64	$ 53	$ 193	$ 2,011