Employee Benefit Plans (Components Of Pension Expense) (Details) - BancShares Plan - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 4,023	$ 3,682	$ 7,676	$ 7,139
Interest cost	7,528	8,568	14,932	17,099
Expected return on assets	(19,621)	(16,435)	(39,216)	(32,844)
Amortization of net actuarial loss	7,018	6,398	13,547	12,662
Total pension expense	$ (1,052)	$ 2,213	$ (3,061)	$ 4,056