Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenue	$ 662,759	$ 605,832	$ 1,331,483	$ 1,206,125
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	235,487	214,680	470,312	420,407
Research and development	59,709	53,373	124,774	105,535
Sales and marketing	131,680	117,944	254,233	232,436
General and administrative	170,206	123,518	324,591	238,527
Amortization of acquired intangible assets	8,294	7,753	16,725	15,322
Restructuring charges	266	2,971	15,174	2,971
Total costs and operating expenses	605,642	520,239	1,205,809	1,015,198
Income from operations	57,117	85,593	125,674	190,927
Interest income	6,409	4,281	10,374	8,905
Interest expense	(9,204)	(4,646)	(14,054)	(9,243)
Other (expense) income, net	(2,769)	563	(2,748)	(121)
Income before provision for income taxes	51,553	85,791	119,246	190,468
Provision for income taxes	8,492	29,039	22,471	59,133
Net income	$ 43,061	$ 56,752	$ 96,775	$ 131,335
Net income per share:
Basic (in dollars per share)	$ 0.25	$ 0.33	$ 0.57	$ 0.76
Diluted (in dollars per share)	$ 0.25	$ 0.33	$ 0.56	$ 0.75
Shares used in per share calculations:
Basic (in shares)	170,250	172,674	170,183	172,916
Diluted (in shares)	172,307	173,439	172,156	174,305