Condensed Consolidated Statements Of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues	$ 287,554	$ 265,780	$ 855,896	$ 786,741
Costs and expenses:
Cost of revenues	49,807	47,218	149,142	143,792
Sales and marketing	18,647	20,966	58,431	67,677
Research and development	14,324	15,019	45,355	48,518
General and administrative	30,000	28,115	85,158	79,090
Total costs and expenses	112,778	111,318	338,086	339,077
Operating income	174,776	154,462	517,810	447,664
Interest expense	(28,919)	(28,544)	(86,582)	(79,064)
Non-operating income (loss), net	3,262	(3,975)	8,092	(6,329)
Income before income taxes	149,119	121,943	439,320	362,271
Income tax expense	(34,692)	(29,486)	(104,227)	(88,565)
Net Income	114,427	92,457	335,093	273,706
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax	0	0	(85)	291
Change in unrealized gain on investments, net of tax	(485)	565	1,301	799
Realized gain on investments, net of tax, included in net income	(11)	(26)	(78)	(99)
Other comprehensive income (loss)	(496)	539	1,308	409
Comprehensive Income	$ 113,931	$ 92,996	$ 336,401	$ 274,115
Basic income (loss) per share
Net Income	$ 1.08	$ 0.82	$ 3.10	$ 2.38
Diluted income (loss) per share
Net Income	$ 0.90	$ 0.70	$ 2.58	$ 2.06
Shares used to compute net income per share
Basic	106,307	112,955	107,982	115,235
Diluted	127,750	131,721	129,967	132,925