Segment Reporting (Summary Of The Operating Information) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 31, 2020	Dec. 28, 2019	Dec. 29, 2018
Segment Reporting Information [Line Items]
Revenue	$ 1,395,025	$ 1,368,673	$ 1,330,349	$ 1,411,741	$ 1,442,232	$ 1,429,428	$ 1,431,061	$ 1,389,877	$ 5,505,788	$ 5,692,598	$ 5,366,325
Cost of revenues									932,941	1,071,041	937,348
Operating expenses									3,878,803	4,020,888	3,654,192
Total costs and expenses									4,811,744	5,091,929	4,591,540
Gain on sale of businesses									220,523	0	0
Operating earnings									914,567	600,669	774,785
Domestic Segment [Member]
Segment Reporting Information [Line Items]
Revenue									4,879,769	5,038,127	4,730,266
Cost of revenues									854,574	967,035	827,904
Operating expenses									2,339,624	2,398,422	2,164,465
Total costs and expenses									3,194,198	3,365,457	2,992,369
Gain on sale of businesses									0
Operating earnings									1,685,571	1,672,670	1,737,897
International Segment [Member]
Segment Reporting Information [Line Items]
Revenue									626,019	654,471	636,059
Cost of revenues									78,367	104,006	109,444
Operating expenses									242,991	276,914	321,116
Total costs and expenses									321,358	380,920	430,560
Gain on sale of businesses									0
Operating earnings									304,661	273,551	205,499
Other
Segment Reporting Information [Line Items]
Operating expenses									1,296,188	1,345,552	1,168,611
Total costs and expenses									1,296,188	1,345,552	1,168,611
Gain on sale of businesses									220,523
Operating earnings									$ (1,075,665)	$ (1,345,552)	$ (1,168,611)