Goodwill and Acquired Intangible Assets - Schedule of Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 370,001	$ 321,121
Accumulated Amortization	(193,713)	(171,658)
Net Carrying Amount	176,288	149,463
Completed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	137,891	119,091
Accumulated Amortization	(61,499)	(50,823)
Net Carrying Amount	76,392	68,268
Customer-related intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	221,010	192,810
Accumulated Amortization	(125,179)	(114,209)
Net Carrying Amount	95,831	78,601
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,510	5,030
Accumulated Amortization	(3,751)	(3,775)
Net Carrying Amount	759	1,255
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,100	3,700
Accumulated Amortization	(2,794)	(2,361)
Net Carrying Amount	3,306	1,339
Acquired license rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	490	490
Accumulated Amortization	(490)	(490)
Net Carrying Amount	$ 0	$ 0