Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Revenue	$ 395,790	$ 345,321	$ 1,141,942	$ 996,075
Costs and operating expenses:
Cost of revenue	132,039	134,221	377,136	390,406
Research and development	24,857	19,351	67,359	54,373
Sales and marketing	67,811	55,206	198,326	160,681
General and administrative	66,634	51,003	183,365	156,241
Amortization of acquired intangible assets	4,859	5,381	16,653	15,611
Restructuring charges	69	0	891	14
Total costs and operating expenses	296,269	265,162	843,730	777,326
Income from operations	99,521	80,159	298,212	218,749
Interest income, net	1,458	1,593	4,543	4,865
Other (expense) income, net	(305)	(241)	(96)	449
Income before provision for income taxes	100,674	81,511	302,659	224,063
Provision for income taxes	20,918	33,280	89,521	88,366
Net income	$ 79,756	$ 48,231	$ 213,138	$ 135,697
Net income per share:
Basic (in dollars per share)	$ 0.45	$ 0.27	$ 1.20	$ 0.76
Diluted (in dollars per share)	$ 0.44	$ 0.27	$ 1.17	$ 0.75
Shares used in per share calculations:
Basic (in shares)	178,235	177,455	178,008	178,040
Diluted (in shares)	181,922	181,053	181,623	181,738