Income Taxes (Schedule Of Components Of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Current, Federal									$ 96,575	$ 90,227	$ 68,651
Deferred, Federal									(46,556)	(5,123)	11,655
Total, Federal									50,019	85,104	80,306
Current, State									33,368	28,125	18,960
Deferred, State									(16,387)	1,579	7,157
State, Total									16,981	29,704	26,117
Current income tax expense (benefit)									129,943	118,352	87,611
Deferred income tax (benefit) expense									(62,943)	(3,544)	18,812
Income tax expense (benefit)	$ (3,204)	$ 33,758	$ 6,062	$ 30,384	$ 27,118	$ 26,166	$ 37,408	$ 24,116	$ 67,000	$ 114,808	$ 106,423