Operating Segments and Geographic Information (Information Related To Reportable Operating Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Total consolidated revenues	$ 283,148	$ 267,907
Income (loss) from operations	25,922	15,582
Foreign currency gains, net	1,071	276
Interest income	279	150
Interest expense	(113)	(184)
Other income, net	53	124
Income before income taxes	27,212	15,948
Total consolidated depreciation and amortization	7,643	8,446
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	282,835	267,717
Income (loss) from operations	72,986	61,002
Total consolidated depreciation and amortization	2,352	2,656
Reportable Operating Segments [Member] | Americas [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	123,830	117,722
Income (loss) from operations	28,539	22,002
Total consolidated depreciation and amortization	1,304	1,345
Reportable Operating Segments [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	97,162	98,344
Income (loss) from operations	26,584	26,726
Total consolidated depreciation and amortization	696	926
Reportable Operating Segments [Member] | Europe [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	61,843	51,651
Income (loss) from operations	17,863	12,274
Total consolidated depreciation and amortization	352	385
Reportable Operating Segments [Member] | Other businesses [Member]
Segment Reporting Information [Line Items]
Total consolidated revenues	313	190
Income (loss) from operations	(10,934)	(5,617)
Total consolidated depreciation and amortization	1,524	1,746
Unallocated corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(36,130)	(39,803)
Total consolidated depreciation and amortization	$ 3,767	$ 4,044