Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Revenues	$ 258,422	$ 248,796
Costs and expenses:
Cost of revenues	48,353	48,026
Sales and marketing	22,382	20,289
Research and development	17,152	18,439
General and administrative	26,298	22,457
Total costs and expenses	114,185	109,211
Operating income	144,237	139,585
Interest expense	(22,017)	(21,385)
Non-operating income (loss), net	(5,555)	6,516
Income before income taxes	116,665	124,716
Income tax expense	(28,427)	(30,293)
Net Income	88,238	94,423
Change in unrealized gain on investments, net of tax	87	8
Realized gain on investments, net of tax, included in net income	(4)	5
Other comprehensive income (loss)	83	13
Comprehensive Income	$ 88,321	$ 94,436
Basic income (loss) per share
Continuing operations	$ 0.75	$ 0.71
Diluted income (loss) per share
Continuing operations	$ 0.66	$ 0.64
Shares used to compute net income per share
Basic	117,139	133,417
Diluted	133,850	148,600