Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 25,714
Cumulative effect of accounting change for adoption of ASU		$ 0	$ 386	$ 2,210
Other comprehensive income (loss)	(30,704)	120,366	36,675
Ending Balance	(6,791)	25,714
Pension and Other Post-Retirement Actuarial Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(69,041)	(64,496)	(136,422)
Cumulative effect of accounting change for adoption of ASU		0
Other comprehensive income before reclassifications	5,617	(15,671)	(32,398)
Tax effect	(1,032)	4,373	9,815
Other comprehensive income before reclassifications, net of tax	4,585	(11,298)	(22,583)
Amounts reclassified out of AOCI	8,343	9,147	91,014
Tax effect	(2,178)	(2,394)	3,495
Amounts reclassified out of AOCI, net of tax	6,165	6,753	94,509
Other comprehensive income (loss)	10,750	(4,545)	71,926
Ending Balance	(58,291)	(69,041)	(64,496)
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	92,954	(31,266)	4,597
Cumulative effect of accounting change for adoption of ASU		0
Other comprehensive income before reclassifications	(41,454)	124,220	(35,863)
Tax effect	0	0	0
Other comprehensive income before reclassifications, net of tax	(41,454)	124,220	(35,863)
Amounts reclassified out of AOCI	0	0	0
Tax effect	0	0	0
Amounts reclassified out of AOCI, net of tax	0	0	0
Other comprehensive income (loss)	(41,454)	124,220	(35,863)
Ending Balance	51,500	92,954	(31,266)
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,801	1,110	498
Cumulative effect of accounting change for adoption of ASU		(1,801)
Other comprehensive income before reclassifications	0	1,881	941
Tax effect	0	(659)	(329)
Other comprehensive income before reclassifications, net of tax	0	1,222	612
Amounts reclassified out of AOCI	0	(817)	0
Tax effect	0	286	0
Amounts reclassified out of AOCI, net of tax	0	(531)	0
Other comprehensive income (loss)	0	691	612
Ending Balance	0	1,801	1,110
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	25,714	(94,652)	(131,327)
Cumulative effect of accounting change for adoption of ASU		(1,801)	0	$ 0
Other comprehensive income before reclassifications	(35,837)	110,430	(67,320)
Tax effect	(1,032)	3,714	9,486
Other comprehensive income before reclassifications, net of tax	(36,869)	114,144	(57,834)
Amounts reclassified out of AOCI	8,343	8,330	91,014
Tax effect	(2,178)	(2,108)	3,495
Amounts reclassified out of AOCI, net of tax	6,165	6,222	94,509
Other comprehensive income (loss)	(30,704)	120,366	36,675
Ending Balance	$ (6,791)	$ 25,714	$ (94,652)