Operating Segments and Geographic Information (Information Related To Reportable Operating Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total consolidated revenues	$ 262,979	$ 312,766	$ 358,899	$ 295,949	$ 215,989	$ 261,064	$ 328,004	$ 283,148	$ 1,230,593	$ 1,088,205	$ 1,023,513
Income (loss) from operations	8,356	$ 39,884	$ 47,831	$ 32,578	(13,937)	$ 13,895	$ 37,064	$ 25,922	128,649	62,944	17,336
Foreign currency gains (losses), net									(1,323)	1,318	563
Interest income									601	1,281	870
Interest expense									(8,636)	(955)	(869)
Other income, net									31	569	280
Income before income taxes									119,322	65,157	18,180
Total consolidated depreciation and amortization									24,213	29,250	33,130
Total property and equipment, net	47,405				22,211				47,405	22,211
Americas
Segment Reporting Information [Line Items]
Total consolidated revenues									640,515	520,192
Asia Pacific
Segment Reporting Information [Line Items]
Total consolidated revenues									348,072	344,598
EMEA
Segment Reporting Information [Line Items]
Total consolidated revenues									241,948	220,270
Other businesses
Segment Reporting Information [Line Items]
Total consolidated revenues									58	3,145
Reportable Operating Segments
Segment Reporting Information [Line Items]
Total consolidated revenues									1,230,535	1,085,060	1,022,643
Income (loss) from operations									355,839	281,259	206,875
Total consolidated depreciation and amortization									5,349	7,941	10,815
Reportable Operating Segments | Americas
Segment Reporting Information [Line Items]
Total consolidated revenues									640,515	520,192	480,146
Income (loss) from operations									204,868	138,940	96,740
Total consolidated depreciation and amortization									3,593	4,640	5,473
Reportable Operating Segments | Asia Pacific
Segment Reporting Information [Line Items]
Total consolidated revenues									348,072	344,598	336,073
Income (loss) from operations									80,645	82,780	72,950
Total consolidated depreciation and amortization									963	2,049	3,405
Reportable Operating Segments | EMEA
Segment Reporting Information [Line Items]
Total consolidated revenues									241,948	220,270	206,424
Income (loss) from operations									70,326	59,539	37,185
Total consolidated depreciation and amortization									793	1,252	1,937
Reportable Operating Segments | Other businesses
Segment Reporting Information [Line Items]
Total consolidated revenues									58	3,145	870
Income (loss) from operations									(54,936)	(55,583)	(22,861)
Total consolidated depreciation and amortization									5,234	5,256	6,748
Unallocated corporate
Segment Reporting Information [Line Items]
Income (loss) from operations									(172,254)	(162,732)	(166,678)
Total consolidated depreciation and amortization									13,630	16,053	15,567
United States
Segment Reporting Information [Line Items]
Total consolidated revenues									563,473	442,544	388,847
Total property and equipment, net	41,745				17,489				41,745	17,489
International
Segment Reporting Information [Line Items]
Total consolidated revenues									667,120	645,661	$ 634,666
Total property and equipment, net	$ 5,660				$ 4,722				$ 5,660	$ 4,722