Segment Reporting (Summary Of The Operating Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 1,387,778	$ 1,411,741
Costs of revenue	230,656	254,416
Operating expenses	939,064	978,949
Total costs and expenses	1,169,720	1,233,365
Operating earnings (loss)	218,058	178,376
Domestic Segment
Segment Reporting Information [Line Items]
Revenues	1,221,992	1,246,415
Costs of revenue	205,694	228,567
Operating expenses	560,562	570,094
Total costs and expenses	766,256	798,661
Operating earnings (loss)	455,736	447,754
International Segment [Member]
Segment Reporting Information [Line Items]
Revenues	165,786	165,326
Costs of revenue	24,962	25,849
Operating expenses	61,614	66,555
Total costs and expenses	86,576	92,404
Operating earnings (loss)	79,210	72,922
Other
Segment Reporting Information [Line Items]
Operating expenses	316,888	342,300
Total costs and expenses	316,888	342,300
Operating earnings (loss)	$ (316,888)	$ (342,300)