Employee Benefit Plans (Components Of Pension Expense) (Details) - BancShares Plan - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 3,653	$ 3,457
Interest cost	7,404	8,531
Expected return on assets	(19,595)	(16,409)
Amortization of net actuarial loss	6,529	6,264
Total pension expense	$ (2,009)	$ 1,843