Pensions and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Defined Benefit Pension Plan [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	371	411	742	821
Expected return on plan assets	0	0	0	0
Amortization of prior service cost (credit)	36	36	72	72
Amortization of losses (gains)	159	83	318	165
Curtailments and settlements	0	0	0	0
Net periodic benefit cost	566	530	1,132	1,058
Defined Benefit Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net service cost	927	925	1,875	1,828
Interest cost	1,211	1,199	2,453	2,366
Expected return on plan assets	(479)	(518)	(967)	(1,024)
Amortization of prior service cost (credit)	54	18	109	36
Amortization of losses (gains)	1,566	1,523	3,170	3,001
Curtailments and settlements	455	330	917	652
Net periodic benefit cost	3,734	3,477	7,557	6,859
Other Postretirement Benefits [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net service cost	34	33	68	66
Interest cost	68	78	136	155
Amortization of prior service cost (credit)	(37)	(209)	(74)	(418)
Amortization of losses (gains)	(9)	(23)	(19)	(46)
Net periodic benefit cost	56	(121)	111	(243)
Other Postretirement Benefits [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net service cost	73	67	148	131
Interest cost	28	26	58	50
Amortization of prior service cost (credit)	0	0	0	0
Amortization of losses (gains)	27	15	54	29
Net periodic benefit cost	$ 128	$ 108	$ 260	$ 210