Pensions and Other Postretirement Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension plans
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	$ 245,800	$ 227,211	$ 201,450
Defined benefit plan, benefit obligation, period increase (decrease)	18,600
Actuarial (gain)/loss	(13,309)	(22,645)
Other postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	47,977	54,384	$ 51,127
Defined benefit plan, benefit obligation, period increase (decrease)	(6,400)
Actuarial (gain)/loss	$ 4,794	$ (4,686)
United States
Defined Benefit Plan Disclosure [Line Items]
Percent of consolidated pension plan assets	44.00%
Percent of consolidated pension plan obligations	45.00%
Accrued postretirement liability	$ 46,700
Switzerland | Pension plans
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	6,000
Canada
Defined Benefit Plan Disclosure [Line Items]
Accrued postretirement liability	$ 1,300