Securities (Schedule of Securities with Unrealized Losses) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	$ 298,342	$ 205,584
Less than 12 Months Unrealized Loss	(7,550)	(2,285)
12 Months or More Fair Value	250,438	274,681
12 Months or More Unrealized Loss	(12,876)	(7,865)
Total Fair Value	548,780	480,265
Total Unrealized Loss	(20,426)	(10,150)
Obligations of State and Political Subdivisions
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	71,937	33,230
Less than 12 Months Unrealized Loss	(1,096)	(237)
12 Months or More Fair Value	23,735	24,161
12 Months or More Unrealized Loss	(934)	(624)
Total Fair Value	95,672	57,391
Total Unrealized Loss	(2,030)	(861)
MBS/CMO - Residential
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	226,405	172,354
Less than 12 Months Unrealized Loss	(6,454)	(2,048)
12 Months or More Fair Value	226,703	250,520
12 Months or More Unrealized Loss	(11,942)	(7,241)
Total Fair Value	453,108	422,874
Total Unrealized Loss	$ (18,396)	$ (9,289)