Defined Benefit Pension Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	$ 561	$ 537
Interest cost	[2]	679	669
Expected return on plan assets	[2]	(1,318)	(1,236)
Amortization of prior service (credit) cost	[2]	(6)	(6)
Recognized net actuarial loss	[2]	374	279
Net periodic benefit cost		290	243
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	27	32
Interest cost	[2]	119	107
Expected return on plan assets	[2]	0	0
Amortization of prior service (credit) cost	[2]	0	0
Recognized net actuarial loss	[2]	102	65
Net periodic benefit cost		$ 248	$ 204

[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.