Operating Segments and Geographic Information (Information Related To Reportable Operating Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total consolidated revenues	$ 328,004	$ 313,221	$ 611,152	$ 581,128
Income (loss) from operations	37,064	29,446	62,986	45,028
Foreign currency gains, net	283	162	1,354	438
Interest income	146	157	425	307
Interest expense	(132)	(188)	(245)	(372)
Other income, net	16	9	69	133
Income before income taxes	37,377	29,586	64,589	45,534
Total consolidated depreciation and amortization	7,231	8,369	14,874	16,815
Americas [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	137,762		261,592
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	128,400		225,562
Europe [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	61,547		123,390
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	327,709	313,118	610,544	580,837
Income (loss) from operations	94,777	82,465	167,763	143,811
Total consolidated depreciation and amortization	2,075	2,646	4,427	5,303
Reportable Operating Segments [Member] | Americas [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	137,762	136,154	261,592	253,877
Income (loss) from operations	39,689	34,426	68,228	56,733
Total consolidated depreciation and amortization	1,211	1,347	2,515	2,692
Reportable Operating Segments [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	128,400	124,644	225,562	222,989
Income (loss) from operations	36,387	36,743	62,971	63,496
Total consolidated depreciation and amortization	537	920	1,233	1,847
Reportable Operating Segments [Member] | Europe [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	61,547	52,320	123,390	103,971
Income (loss) from operations	18,701	11,296	36,564	23,582
Total consolidated depreciation and amortization	327	379	679	764
Reportable Operating Segments [Member] | Other businesses [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	295	103	608	291
Income (loss) from operations	(16,531)	(5,035)	(27,465)	(10,650)
Total consolidated depreciation and amortization	1,431	1,741	2,955	3,488
Unallocated corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(41,182)	(47,984)	(77,312)	(88,133)
Total consolidated depreciation and amortization	$ 3,725	$ 3,982	$ 7,492	$ 8,024