Employee Benefit Plans (Components Of Pension Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
BancShares Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 3,153	$ 3,358	$ 9,463	$ 10,561
Interest cost	7,218	6,732	21,668	20,230
Expected return on assets	(9,155)	(8,302)	(27,481)	(24,896)
Amortization of prior service cost	54	53	158	158
Amortization of net actuarial loss	1,714	2,863	5,144	8,531
Total pension expense	2,984	4,704	8,952	14,584
Bancorporation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	642	641	1,925	2,506
Interest cost	1,694	1,540	5,081	4,795
Expected return on assets	(2,775)	(2,873)	(8,325)	(8,612)
Total pension expense	$ (439)	$ (692)	$ (1,319)	$ (1,311)