Employee Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Recognized in other comprehensive (loss) income	[1]	$ (2,948)	$ 13,493	$ (20,406)
Qualified Pension Plan [Member]
Net Periodic Benefit Cost:
Service cost		2,459	2,152	2,720
Interest cost		2,928	2,891	2,883
Expected return on plan assets		(4,515)	(4,063)	(3,725)
Amortization of prior service credit		(23)	(23)	(30)
Recognized net actuarial loss		1,249	461	1,321
Curtailments		0	0	(61)
Net periodic benefit cost		2,098	1,418	3,108
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		(2,816)	10,993	(14,572)
Prior service cost		23	23	30
Curtailment		0	0	(4,000)
Recognized in other comprehensive (loss) income		(2,793)	11,016	(18,542)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		(695)	12,434	(15,434)
Non-Qualified Retirement Plans [Member]
Net Periodic Benefit Cost:
Service cost		78	46	181
Interest cost		490	478	462
Expected return on plan assets		0	0	0
Amortization of prior service credit		(1)	(1)	(1)
Recognized net actuarial loss		245	70	175
Curtailments		0	0	(1)
Net periodic benefit cost		812	593	816
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		(156)	2,476	(1,506)
Prior service cost		1	1	1
Curtailment		0	0	(359)
Recognized in other comprehensive (loss) income		(155)	2,477	(1,864)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		$ 657	$ 3,070	$ (1,048)

[1] Included in salaries and employee benefits expense in the Consolidated Statements of Income.