Employee Benefit Plans (Components Of Pension Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
BancShares Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 3,358	$ 3,081	$ 10,561	$ 9,247
Interest cost	6,732	6,402	20,230	19,209
Expected return on assets	(8,302)	(7,296)	(24,896)	(23,448)
Amortization of prior service cost	53	53	158	158
Amortization of net actuarial loss	2,863	769	8,531	3,861
Total pension expense	4,704	$ 3,009	14,584	$ 9,027
Bancorporation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	641		2,506
Interest cost	1,540		4,795
Expected return on assets	(2,873)		(8,612)
Amortization of prior service cost	0		0
Amortization of net actuarial loss	0		0
Total pension expense	$ (692)		$ (1,311)