Pensions and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement loss		$ 0	$ 0	$ 0	$ (673)	$ 0	$ 0	$ 0
Estimated actuarial items that will be amortized from AOCI loss	$ 400								$ 400
Ultimate health care cost trend rate	3.90%								3.90%
Defined benefit plan, employer contribution in 2020	$ 1,500								$ 1,500
Defined contribution plan matching expense									700	$ 700	$ 700
Accrued pension and other postretirement costs	15,669				14,982				15,669	14,982
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued pension and other postretirement costs	10,851				9,421				10,851	9,421
Other Retirement Obligations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other retirement obligations	900				1,300				900	1,300
Accrued pension and other postretirement costs	4,633				4,645				4,633	4,645
Foreign Plan | Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement loss									700
Nonqualified Plan | Deferred Compensation, Excluding Share-based Payments and Retirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assets held-in-trust	3,500				3,100				3,500	3,100
Accrued pension and other postretirement costs	4,900				4,200				4,900	4,200
Unfunded Plan | Nonqualified Plan | United States | Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assets held-in-trust	1,700				1,600				1,700	1,600
Non qualified pension plan liabilities	$ 2,400				$ 2,200				$ 2,400	$ 2,200