Securities (Schedule of Securities with Unrealized Losses) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	$ 283,315	$ 205,584
Less than 12 Months Unrealized Loss	(7,074)	(2,285)
12 Months or More Fair Value	306,330	274,681
12 Months or More Unrealized Loss	(17,053)	(7,865)
Total Fair Value	589,645	480,265
Total Unrealized Loss	(24,127)	(10,150)
Obligations of State and Political Subdivisions
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	109,010	33,230
Less than 12 Months Unrealized Loss	(2,085)	(237)
12 Months or More Fair Value	27,524	24,161
12 Months or More Unrealized Loss	(1,340)	(624)
Total Fair Value	136,534	57,391
Total Unrealized Loss	(3,425)	(861)
MBS/CMO - Residential
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	174,305	172,354
Less than 12 Months Unrealized Loss	(4,989)	(2,048)
12 Months or More Fair Value	278,806	250,520
12 Months or More Unrealized Loss	(15,713)	(7,241)
Total Fair Value	453,111	422,874
Total Unrealized Loss	$ (20,702)	$ (9,289)