Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 705,074	$ 662,759	$ 1,411,582	$ 1,331,483
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	242,193	235,487	482,936	470,312
Research and development	61,439	59,709	127,580	124,774
Sales and marketing	135,106	131,680	261,382	254,233
General and administrative	120,116	170,206	242,951	324,591
Amortization of acquired intangible assets	9,648	8,294	19,247	16,725
Restructuring charges	790	266	7,179	15,174
Total costs and operating expenses	569,292	605,642	1,141,275	1,205,809
Income from operations	135,782	57,117	270,307	125,674
Interest income	6,410	6,409	15,045	10,374
Interest expense	(8,446)	(9,204)	(20,562)	(14,054)
Other expense, net	(578)	(2,769)	(67)	(2,748)
Income before provision for income taxes	133,168	51,553	264,723	119,246
Provision for income taxes	19,253	8,492	43,678	22,471
Net income	$ 113,915	$ 43,061	$ 221,045	$ 96,775
Net income per share:
Basic (in dollars per share)	$ 0.70	$ 0.25	$ 1.35	$ 0.57
Diluted (in dollars per share)	$ 0.69	$ 0.25	$ 1.34	$ 0.56
Shares used in per share calculations:
Basic (in shares)	163,407	170,250	163,322	170,183
Diluted (in shares)	165,019	172,307	164,903	172,156