Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenues	$ 1,010,117	$ 965,087	$ 873,592
Costs and expenses:
Cost of revenues	188,425	187,013	167,600
Sales and marketing	92,001	89,337	97,809
Research and development	67,777	70,297	61,694
General and administrative	97,487	90,208	89,162
Total costs and expenses	445,690	436,855	416,265
Operating income	564,427	528,232	457,327
Interest expense	(85,994)	(74,761)	(50,196)
Non-operating income, net	4,878	3,300	5,564
Income from continuing operations before income taxes	483,311	456,771	412,695
Income tax (expense) benefit	(128,051)	87,679	(100,210)
Income from continuing operations, net of tax	355,260	544,450	312,485
Income from discontinued operations, net of tax	0	0	7,547
Net income	355,260	544,450	320,032
Realized foreign currency translation adjustments, included in net income	0	81	0
Change in unrealized gain on investments, net of tax	84	(369)	2,757
Realized gain on investments, net of tax, included in net income	3	(2,409)	(61)
Other comprehensive income (loss)	87	(2,697)	2,696
Comprehensive income	$ 355,347	$ 541,753	$ 322,728
Basic income per share
Continuing operations	$ 2.80	$ 3.77	$ 1.99
Discontinued operations	$ 0.00	$ 0.00	$ 0.05
Net income	$ 2.80	$ 3.77	$ 2.04
Diluted income per share
Continuing operations	$ 2.52	$ 3.49	$ 1.91
Discontinued operations	$ 0.00	$ 0.00	$ 0.04
Net income	$ 2.52	$ 3.49	$ 1.95
Shares used to compute net income per share
Basic	126,710	144,591	156,953
Diluted	140,895	155,786	163,909