Pension and Postretirement Benefits (Change in Benefit Obligation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Postretirement Medical Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance — January 1	$ 18,810	$ 23,882
Interest cost	754	779	$ 919
Actuarial loss (gain)	2,222	(2,662)
Benefits paid	(3,902)	(4,199)
Employee contributions	964	883
Medicare subsidies receivable	14	127
Balance — December 31	18,862	18,810	23,882
United States | Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance — January 1	432,595	461,355
Service cost	23,245	22,195	22,257
Interest cost	17,584	15,789	16,878
Plan amendments and settlements	276	(3,016)
Actuarial loss (gain)	31,214	(25,908)
Benefits paid	(33,452)	(37,820)
Balance — December 31	471,462	432,595	461,355
Accumulated benefit obligations	470,643	431,973
Foreign Plan | Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance — January 1	376,649	413,960
Service cost	5,728	7,208	7,247
Interest cost	8,867	8,970	9,320
Actuarial loss (gain)	48,888	(8,839)
Benefits paid	(14,526)	(16,632)
Employee contributions	78	238
Settlements and other	(3,713)	(7,896)
Currency translation impact	3,646	(20,360)
Balance — December 31	425,617	376,649	$ 413,960
Accumulated benefit obligations	$ 404,035	$ 356,989