Non-pension Post-retirement Benefits (Change in Accumulated Benefit Obligation) (Details) - Non-pension Post-retirement Benefit Plans - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Change in projected benefit obligation:
Projected benefit obligation, beginning of year	$ 53,943	$ 60,265
Service cost	605	632
Interest cost	1,860	2,148
Plan participants' contributions	512	525
Actuarial (gain) loss	(5,411)	(5,591)
Exchange rate fluctuations	(96)	90
Benefits paid	(4,447)	(4,126)
Projected benefit obligation, end of year	46,966	53,943
Funded status and accrued benefit cost	(46,966)	(53,943)
U.S. Plans
Change in projected benefit obligation:
Projected benefit obligation, beginning of year	52,648	58,921
Service cost	604	631
Interest cost	1,822	2,104
Plan participants' contributions	512	525
Actuarial (gain) loss	(5,305)	(5,483)
Exchange rate fluctuations	0	0
Benefits paid	(4,382)	(4,050)
Projected benefit obligation, end of year	45,899	52,648
Funded status and accrued benefit cost	(45,899)	(52,648)
Non-U.S. Plans
Change in projected benefit obligation:
Projected benefit obligation, beginning of year	1,295	1,344
Service cost	1	1
Interest cost	38	44
Plan participants' contributions	0	0
Actuarial (gain) loss	(106)	(108)
Exchange rate fluctuations	(96)	90
Benefits paid	(65)	(76)
Projected benefit obligation, end of year	1,067	1,295
Funded status and accrued benefit cost	$ (1,067)	$ (1,295)