Supplemental Financial Statement Information - Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Financial Statement Information [Abstract]
Net cash paid for income taxes	$ 16,342	$ 23,279	$ 6,812
Cash paid for interest expense	3,138	3,174	2,975
Cash paid for businesses and technology purchased, excluding contingent consideration	0	30,230	21,560
Cash acquired in business acquisitions	0	(671)	(1,628)
Net cash paid for business acquisitions	0	29,559	19,932
Common stock issued in connection with business acquisitions	(123)	0	73
Non-cash settlement of employee-related liabilities by issuing RSUs	0	1,171	3,059
Property and equipment received, but not paid	$ 1,185	$ 681	$ 1,257