Employee Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		$ 4,106	$ (1,478)	$ 14,000
Prior service cost	[1]	(15)	(17)	(16)
Recognized in other comprehensive (loss) income		(3,055)	2,948	(13,493)
Qualified Pension Plan [Member]
Net Periodic Benefit Cost:
Service cost		2,148	2,459	2,152
Interest cost		2,576	2,928	2,891
Expected return on plan assets		(4,633)	(4,515)	(4,063)
Amortization of prior service credit		(23)	(23)	(23)
Recognized net actuarial loss		828	1,249	461
Net periodic benefit cost		896	2,098	1,418
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		2,904	(2,816)	10,993
Prior service cost		23	23	23
Recognized in other comprehensive (loss) income		2,927	(2,793)	11,016
Total recognized in net periodic benefit cost and other comprehensive income (loss)		3,823	(695)	12,434
Non-Qualified Retirement Plans [Member]
Net Periodic Benefit Cost:
Service cost		122	78	46
Interest cost		432	490	478
Expected return on plan assets		0	0	0
Amortization of prior service credit		(1)	(1)	(1)
Recognized net actuarial loss		247	245	70
Net periodic benefit cost		800	812	593
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		127	(156)	2,476
Prior service cost		1	1	1
Recognized in other comprehensive (loss) income		128	(155)	2,477
Total recognized in net periodic benefit cost and other comprehensive income (loss)		$ 928	$ 657	$ 3,070

[1] The pre-tax amount is included in salaries and employee benefits expense in the Consolidated Statements of Income.