Employee Benefit Plans (Components Of Pension Expense) (Details) - BancShares Plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 3,570	$ 3,191	$ 10,709	$ 9,575
Interest cost	8,549	9,316	25,648	27,945
Expected return on assets	(16,423)	(15,647)	(49,267)	(46,943)
Amortization of prior service cost	0	15	0	43
Amortization of net actuarial loss	6,332	2,730	18,994	8,192
Total pension expense	$ 2,028	$ (395)	$ 6,084	$ (1,188)