Operating Segments and Geographic Information (Information Related To Reportable Operating Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total consolidated revenues	$ 313,221	$ 323,828	$ 581,128	$ 602,968
Income (loss) from operations	29,446	20,605	45,028	34,848
Foreign currency gain (loss), net	162	(1,700)	438	(2,947)
Interest income	157	164	307	380
Interest expense	(188)	(234)	(372)	(477)
Other income (loss)	9	(189)	133	(107)
Income before income taxes	29,586	18,646	45,534	31,697
Depreciation and amortization	8,369	8,451	16,815	17,031
Other businesses [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	103	225	291	397
Income (loss) from operations	(5,035)	(6,038)	(10,650)	(12,111)
Depreciation and amortization	1,741	1,736	3,488	3,446
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	313,118	323,603	580,837	602,571
Income (loss) from operations	68,541	60,985	129,542	109,935
Depreciation and amortization	2,646	3,214	5,303	6,549
Reportable Operating Segments [Member] | Americas [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	136,154	135,097	253,877	259,227
Income (loss) from operations	25,205	18,015	47,207	34,592
Depreciation and amortization	1,347	1,504	2,692	2,982
Reportable Operating Segments [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	124,644	130,846	222,989	235,347
Income (loss) from operations	33,305	34,533	60,030	60,383
Depreciation and amortization	920	992	1,847	2,070
Reportable Operating Segments [Member] | Europe [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	52,320	57,660	103,971	107,997
Income (loss) from operations	10,031	8,437	22,305	14,960
Depreciation and amortization	379	718	764	1,497
Unallocated corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(34,060)	(34,342)	(73,864)	(62,976)
Depreciation and amortization	$ 3,982	$ 3,501	$ 8,024	$ 7,036