Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Revenues	$ 255,022	$ 243,678	$ 754,200	$ 719,457
Costs and expenses:
Cost of revenues	46,933	46,554	140,948	140,438
Sales and marketing	24,304	22,900	68,244	64,273
Research and development	16,320	17,456	50,453	52,531
General and administrative	27,965	24,055	72,349	64,157
Total costs and expenses	115,522	110,965	331,994	321,399
Operating income	139,500	132,713	422,206	398,058
Interest expense	(21,533)	(21,119)	(64,408)	(53,524)
Non-operating income (loss), net	(6,473)	(4,592)	5,037	(4,208)
Income before income taxes	111,494	107,002	362,835	340,326
Income tax expense	(16,305)	(26,104)	(73,047)	(88,025)
Net Income	95,189	80,898	289,788	252,301
Change in unrealized gain on investments, net of tax	59	85	34	(341)
Realized gain on investments, net of tax, included in net income	(1)	1	2	(2,478)
Other comprehensive income (loss)	58	86	36	(2,819)
Comprehensive Income	$ 95,247	$ 80,984	$ 289,824	$ 249,482
Basic income (loss) per share
Continuing operations	$ 0.77	$ 0.57	$ 2.25	$ 1.71
Diluted income (loss) per share
Continuing operations	$ 0.69	$ 0.53	$ 2.03	$ 1.60
Shares used to compute net income per share
Basic	124,109	141,701	128,924	147,567
Diluted	138,112	152,951	142,584	157,606