Condensed Consolidated Statements Of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenues	$ 265,780	$ 255,022	$ 786,741	$ 754,200
Costs and expenses:
Cost of revenues	47,218	46,933	143,792	140,948
Sales and marketing	20,966	24,304	67,677	68,244
Research and development	15,019	16,320	48,518	50,453
General and administrative	28,115	27,965	79,090	72,349
Total costs and expenses	111,318	115,522	339,077	331,994
Operating income	154,462	139,500	447,664	422,206
Interest expense	(28,544)	(21,533)	(79,064)	(64,408)
Non-operating income (loss), net	(3,975)	(6,473)	(6,329)	5,037
Income before income taxes	121,943	111,494	362,271	362,835
Income tax expense	(29,486)	(16,305)	(88,565)	(73,047)
Net Income	92,457	95,189	273,706	289,788
Realized foreign currency translation adjustments, included in net income	0	0	(291)	0
Change in unrealized gain on investments, net of tax	565	59	799	34
Realized gain on investments, net of tax, included in net income	(26)	(1)	(99)	2
Other comprehensive income (loss)	539	58	409	36
Comprehensive Income	$ 92,996	$ 95,247	$ 274,115	$ 289,824
Basic income (loss) per share
Continuing operations	$ 0.82	$ 0.77	$ 2.38	$ 2.25
Diluted income (loss) per share
Continuing operations	$ 0.70	$ 0.69	$ 2.06	$ 2.03
Shares used to compute net income per share
Basic	112,955	124,109	115,235	128,924
Diluted	131,721	138,112	132,925	142,584