Securities (Schedule of Securities with Unrealized Losses) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	$ 297,627	$ 205,584
Less than 12 Months Unrealized Loss	(6,644)	(2,285)
12 Months or More Fair Value	260,442	274,681
12 Months or More Unrealized Loss	(12,048)	(7,865)
Total Fair Value	558,069	480,265
Total Unrealized Loss	(18,692)	(10,150)
Obligations of State and Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	74,634	33,230
Less than 12 Months Unrealized Loss	(1,264)	(237)
12 Months or More Fair Value	23,716	24,161
12 Months or More Unrealized Loss	(1,011)	(624)
Total Fair Value	98,350	57,391
Total Unrealized Loss	(2,275)	(861)
MBS/CMO - Residential
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	222,993	172,354
Less than 12 Months Unrealized Loss	(5,380)	(2,048)
12 Months or More Fair Value	236,726	250,520
12 Months or More Unrealized Loss	(11,037)	(7,241)
Total Fair Value	459,719	422,874
Total Unrealized Loss	$ (16,417)	$ (9,289)