Employee Benefit Plans (Components Of Pension Expense) (Details) - BancShares Plan - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 3,682	$ 3,271	$ 7,139	$ 6,384
Interest cost	8,568	9,338	17,099	18,629
Expected return on assets	(16,435)	(15,661)	(32,844)	(31,296)
Amortization of prior service cost	0	14	0	28
Amortization of net actuarial loss	6,398	2,721	12,662	5,462
Total pension expense	$ 2,213	$ (317)	$ 4,056	$ (793)