Condensed Consolidated Statements Of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues	$ 329,405	$ 314,365	$ 653,026	$ 626,889
Costs and expenses:
Cost of revenues	47,796	43,608	94,764	89,181
Sales and marketing	10,221	8,890	18,705	15,494
Research and development	19,808	18,202	40,119	35,560
General and administrative	38,601	36,885	76,052	73,610
Total costs and expenses	116,426	107,585	229,640	213,845
Operating income	212,979	206,780	423,386	413,044
Interest expense	(23,064)	(22,535)	(45,598)	(45,070)
Non-operating income (loss), net	(2,041)	7,403	(1,597)	14,487
Income before income taxes	187,874	191,648	376,191	382,461
Income tax expense	(40,102)	(39,169)	(78,065)	104,134
Net Income	147,772	152,479	298,126	486,595
Other comprehensive income (loss)	(87)	(2,000)	(78)	263
Comprehensive Income	$ 147,685	$ 150,479	$ 298,048	$ 486,858
Basic income (loss) per share
Net Income	$ 1.31	$ 1.32	$ 2.64	$ 4.20
Diluted income (loss) per share
Net Income	$ 1.31	$ 1.32	$ 2.64	$ 4.19
Shares used to compute net income per share
Basic	112,387	115,347	112,757	115,861
Diluted	112,517	115,544	112,905	116,137