Revisions To Financial Statements (Schedule Of Prior Period Financial Statements - Operations And Comprehensive Income (Loss)) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
REVENUES:
Other income (expense)	$ (32,490)	$ (18,225)	$ (9,127)	$ (21,525)
Total revenues	2,244,515	2,008,727	4,226,531	3,974,563
INCOME (LOSS) BEFORE TAXES	237,067	372,345	193,445	786,889
Income tax expense (benefit)	46,187	39,477	(14,047)	99,470
NET INCOME (LOSS)	190,880	332,868	207,492	687,419
COMPREHENSIVE INCOME (LOSS)	$ 757,768	$ 504,077	$ 476,476	$ 1,105,074
EARNINGS PER COMMON SHARE:
Basic	$ 4.78	$ 8.17	$ 5.14	$ 16.88
Diluted	$ 4.77	$ 8.15	$ 5.13	$ 16.82
As Previously Reported [Member]
REVENUES:
Other income (expense)		$ (7,977)		$ (17,030)
Total revenues		2,018,975		3,979,058
INCOME (LOSS) BEFORE TAXES		382,593		791,384
Income tax expense (benefit)		39,738		99,629
NET INCOME (LOSS)		342,855		691,755
COMPREHENSIVE INCOME (LOSS)		$ 514,064		$ 1,109,410
EARNINGS PER COMMON SHARE:
Basic		$ 8.42		$ 16.98
Diluted		$ 8.39		$ 16.93
Impact of Revisions [Member]
REVENUES:
Other income (expense)		$ (10,248)		$ (4,495)
Total revenues		(10,248)		(4,495)
INCOME (LOSS) BEFORE TAXES		(10,248)		(4,495)
Income tax expense (benefit)		(261)		(159)
NET INCOME (LOSS)		(9,987)		(4,336)
COMPREHENSIVE INCOME (LOSS)		$ (9,987)		$ (4,336)
EARNINGS PER COMMON SHARE:
Basic		$ (0.25)		$ (0.10)
Diluted		$ (0.24)		$ (0.11)