Segment Reporting (Summary Of The Operating Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 1,456,755	$ 1,330,349	$ 2,844,533	$ 2,742,090
Costs of revenue	261,325	211,963	491,981	466,379
Operating expenses	1,145,870	971,488	2,084,934	1,950,437
Total costs and expenses	1,407,195	1,183,451	2,576,915	2,416,816
Operating earnings (loss)	49,560	146,898	267,618	325,274
Domestic Segment
Segment Reporting Information [Line Items]
Revenues	1,267,027	1,168,213	2,489,019	2,414,628
Costs of revenue	232,225	189,779	437,919	418,346
Operating expenses	656,369	587,674	1,216,931	1,157,768
Total costs and expenses	888,594	777,453	1,654,850	1,576,114
Operating earnings (loss)	378,433	390,760	834,169	838,514
International Segment [Member]
Segment Reporting Information [Line Items]
Revenues	189,728	162,136	355,514	327,462
Costs of revenue	29,100	22,184	54,062	48,033
Operating expenses	74,708	57,413	136,322	123,968
Total costs and expenses	103,808	79,597	190,384	172,001
Operating earnings (loss)	85,920	82,539	165,130	155,461
Other
Segment Reporting Information [Line Items]
Operating expenses	414,793	326,401	731,681	668,701
Total costs and expenses	414,793	326,401	731,681	668,701
Operating earnings (loss)	$ (414,793)	$ (326,401)	$ (731,681)	$ (668,701)