Retirement Plans and Postretirement Medical Benefits (Components of Net Periodic Benefit Cost for Defined Benefit Pension Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Nonpension postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,405	$ 1,727	$ 2,046
Interest cost	6,640	7,100	7,969
Amortization of prior service credit	304	297	297
Amortization of net actuarial loss	3,048	3,600	3,615
Curtailment	246	0	0
Net periodic benefit cost (income)	11,643	12,724	13,927
United States | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	92	132	105
Interest cost	61,490	68,611	73,699
Expected return on plan assets	(101,087)	(97,656)	(101,918)
Amortization of net transition asset	0	0	0
Amortization of prior service credit	(60)	(60)	(60)
Amortization of net actuarial loss	31,298	28,954	27,220
Special termination benefits	0	0	0
Settlement/Curtailment	44,665	0	2,109
Net periodic benefit cost (income)	36,398	(19)	1,155
Foreign | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,159	2,274	2,148
Interest cost	18,089	18,836	21,886
Expected return on plan assets	(35,687)	(32,242)	(32,615)
Amortization of net transition asset	(7)	(8)	(8)
Amortization of prior service credit	(71)	(71)	(73)
Amortization of net actuarial loss	7,264	8,052	5,264
Special termination benefits	208	0	52
Settlement/Curtailment	(13)	0	110
Net periodic benefit cost (income)	$ (8,058)	$ (3,159)	$ (3,236)