Employee Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 05, 2020	Jun. 30, 2019	Jul. 05, 2020	Jun. 30, 2019
nora Defined Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 259	$ 216	$ 517	$ 433
Interest cost	110	171	221	345
Amortization of net actuarial losses	110	0	110	0
Net periodic benefit cost	479	387	848	778
Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plan, Contributions by Employer	600		1,300
Service cost	0	184	0	369
Interest cost	870	1,266	1,761	2,547
Expected return on assets	(1,038)	(1,428)	(2,102)	(2,873)
Amortization of prior service cost	26	16	52	32
Amortization of net actuarial losses	320	249	646	502
Net periodic benefit cost	178	287	357	577
United States | Salary Continuation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	235	289	469	577
Amortization of net actuarial losses	139	93	279	187
Net periodic benefit cost	$ 374	$ 382	$ 748	$ 764