Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Revenues	$ 239,332	$ 214,142	$ 475,779	$ 419,868
Costs and expenses:
Cost of revenues	46,630	42,844	93,884	84,100
Sales and marketing	23,269	26,313	41,373	54,128
Research and development	16,899	15,461	35,075	30,226
General and administrative	20,453	22,726	40,102	46,234
Restructuring charges	0	(182)	0	(730)
Total costs and expenses	107,251	107,162	210,434	213,958
Operating income	132,081	106,980	265,345	205,910
Interest expense	(19,809)	(12,580)	(32,405)	(24,920)
Non-operating income (loss), net	6,161	(2,097)	384	(1,290)
Income from continuing operations before income taxes	118,433	92,303	233,324	179,700
Income tax expense	(31,543)	(23,831)	(61,921)	(45,123)
Income from continuing operations, net of tax	86,890	68,472	171,403	134,577
Income (loss) from discontinued operations, net of tax	0	0	0	1,904
Net income	86,890	68,472	171,403	136,481
Change in unrealized gain on investments, net of tax	(159)	42	(426)	37
Realized gain on investments, net of tax, included in net income	(2,459)	(30)	(2,479)	(35)
Other comprehensive income (loss)	(2,618)	12	(2,905)	2
Comprehensive income	$ 84,272	$ 68,484	$ 168,498	$ 136,483
Basic income (loss) per share
Continuing operations	$ 0.58	$ 0.43	$ 1.14	$ 0.85
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.01
Net income	$ 0.58	$ 0.43	$ 1.14	$ 0.86
Diluted income (loss) per share
Continuing operations	$ 0.55	$ 0.42	$ 1.07	$ 0.82
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.01
Net income	$ 0.55	$ 0.42	$ 1.07	$ 0.83
Shares used to compute net income per share
Basic	148,576	157,599	150,549	158,471
Diluted	158,641	164,178	159,982	163,530