Pensions and Other Postretirement Benefit Plans (Schedule of Funded Status of Plans and Composition of Accrued Pension Cost) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Noncurrent asset	$ 16,200	$ 7,800
U.S. Pension Plans with Pension Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	(6,466)
U.S. Pension Plans without Pension Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	(7,356)
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	(13,822)
Non-U.S. Pension Plans with Pension Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	13,870
Non-U.S. Pension Plans without Pension Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	(25,373)
Non-U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	(11,503)
Pension Plans with Pension Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	7,404
Pension Plans without Pension Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Net amount recognized	(32,729)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	205,586	180,672	$ 171,387
Benefit obligation	230,911	210,856	199,856
Funded status	(25,325)	(30,184)
Noncurrent asset	16,242	7,794
Current liability	(2,094)	(2,057)
Noncurrent liability	(39,473)	(35,921)
Net amount recognized	(25,325)	(30,184)
Net actuarial loss	67,283	72,400
Prior service cost/(credit)	572	597
Net amount recognized	67,855	72,997
Other postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Benefit obligation	58,531	57,488	$ 59,970
Funded status	(58,531)	(57,488)
Noncurrent asset
Current liability	(4,108)	(4,195)
Noncurrent liability	(54,423)	(53,293)
Net amount recognized	(58,531)	(57,488)
Net actuarial loss	34,717	34,782
Prior service cost/(credit)	(26,411)	(30,899)
Net amount recognized	$ 8,306	$ 3,883