Segment Reporting (Summary Of The Operating Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 1,467,976	$ 1,368,673	$ 4,312,509	$ 4,110,763
Costs of revenue	251,111	231,889	743,092	698,268
Operating expenses	991,942	941,833	3,076,876	2,892,270
Total costs and expenses	1,243,053	1,173,722	3,819,968	3,590,538
Gain on sale of businesses	0	216,869	0	216,869
Operating earnings (loss)	224,923	411,820	492,541	737,094
Domestic Segment
Segment Reporting Information [Line Items]
Revenues	1,285,488	1,230,769	3,774,507	3,645,397
Costs of revenue	222,665	219,938	660,584	638,284
Operating expenses	580,535	566,777	1,797,466	1,724,545
Total costs and expenses	803,200	786,715	2,458,050	2,362,829
Gain on sale of businesses		0		0
Operating earnings (loss)	482,288	444,054	1,316,457	1,282,568
International Segment [Member]
Segment Reporting Information [Line Items]
Revenues	182,488	137,904	538,002	465,366
Costs of revenue	28,446	11,951	82,508	59,984
Operating expenses	70,472	58,626	206,794	182,594
Total costs and expenses	98,918	70,577	289,302	242,578
Gain on sale of businesses		0		0
Operating earnings (loss)	83,570	67,327	248,700	222,788
Other
Segment Reporting Information [Line Items]
Operating expenses	340,935	316,430	1,072,616	985,131
Total costs and expenses	340,935	316,430	1,072,616	985,131
Gain on sale of businesses		216,869		216,869
Operating earnings (loss)	$ (340,935)	$ (99,561)	$ (1,072,616)	$ (768,262)