Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]
Revenue	$ 1,577,922	$ 1,373,947	$ 1,158,538
Costs and operating expenses:
Cost of revenue	511,087	529,900	453,705
Research and development	93,879	74,744	52,333
Sales and marketing	280,380	223,348	163,017
General and administrative	255,218	210,100	176,878
Amortization of acquired intangible assets	21,547	20,962	17,070
Restructuring charges	1,843	406	4,886
Total costs and operating expenses	1,163,954	1,059,460	867,889
Income from operations	413,968	314,487	290,649
Interest income, net	6,077	6,455	10,421
Other (expense) income, net	(491)	649	6,125
Income before provision for income taxes	419,554	321,591	307,195
Provision for income taxes	126,067	117,602	106,291
Net income	$ 293,487	$ 203,989	$ 200,904
Net income per share:
Basic (in dollars per share)	$ 1.65	$ 1.15	$ 1.09
Diluted (in dollars per share)	$ 1.61	$ 1.12	$ 1.07
Shares used in per share calculations:
Basic (in shares)	178,196	177,900	183,866
Diluted (in shares)	181,783	181,749	187,556