Defined Benefit Pension Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	$ 561	$ 537	$ 1,122	$ 1,074
Interest cost	[2]	678	667	1,357	1,336
Expected return on plan assets	[2]	(1,318)	(1,235)	(2,636)	(2,471)
Amortization of prior service (credit) cost	[2]	(5)	(5)	(11)	(11)
Recognized net actuarial loss	[2]	374	278	748	557
Net periodic benefit cost		290	242	580	485
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	27	33	54	65
Interest cost	[2]	118	107	237	214
Expected return on plan assets	[2]	0	0	0	0
Amortization of prior service (credit) cost	[2]	0	0	0	0
Recognized net actuarial loss	[2]	103	128	205	193
Net periodic benefit cost		$ 248	$ 268	$ 496	$ 472

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

[2] Included in other expenses in the Unaudited Consolidated Statements of Income.