Employee Benefit Plans (Components Of Pension Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
BancShares Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 3,376	$ 3,220
Interest cost	7,380	7,180
Expected return on assets	(10,698)	(9,159)
Amortization of prior service cost	52	52
Amortization of net actuarial loss	2,234	1,600
Total pension expense	2,344	2,893
Bancorporation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	671	650
Interest cost	1,683	1,675
Expected return on assets	(2,796)	(2,779)
Amortization of net actuarial loss	214	0
Total pension expense	$ (228)	$ (454)