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
	Mar. 31, 2020	Mar. 31, 2019
REVENUES:
Other income (expense)	$ 23,363	$ (3,300)
Total revenues	1,982,016	1,965,836
INCOME (LOSS) BEFORE TAXES	(43,622)	414,544
Income tax expense (benefit)	(60,234)	59,993
NET INCOME (LOSS)	16,612	354,551
COMPREHENSIVE INCOME (LOSS)	$ (281,291)	$ 600,997
EARNINGS PER COMMON SHARE:
Basic	$ 0.41	$ 8.70
Diluted	$ 0.41	$ 8.67
As Previously Reported [Member]
REVENUES:
Other income (expense)		$ (9,053)
Total revenues		1,960,083
INCOME (LOSS) BEFORE TAXES		408,791
Income tax expense (benefit)		59,891
NET INCOME (LOSS)		348,900
COMPREHENSIVE INCOME (LOSS)		$ 595,346
EARNINGS PER COMMON SHARE:
Basic		$ 8.57
Diluted		$ 8.54
Impact of Revisions [Member]
REVENUES:
Other income (expense)		$ 5,753
Total revenues		5,753
INCOME (LOSS) BEFORE TAXES		5,753
Income tax expense (benefit)		102
NET INCOME (LOSS)		5,651
COMPREHENSIVE INCOME (LOSS)		$ 5,651
EARNINGS PER COMMON SHARE:
Basic		$ 0.13
Diluted		$ 0.13