Investment Securities - Portfolio of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	$ 83,739	$ 98,211
Gross Unrealized Gains	1,182	735
Gross Unrealized Losses	282	685
Fair Value	84,639	98,261
Obligations of state and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	36,080	40,515
Gross Unrealized Gains	658	309
Gross Unrealized Losses	0	39
Fair Value	36,738	40,785
GSE mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	37,729	44,375
Gross Unrealized Gains	524	426
Gross Unrealized Losses	59	311
Fair Value	38,194	44,490
Collateralized mortgage obligations: residential
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	7,819	8,969
Gross Unrealized Gains	0	0
Gross Unrealized Losses	223	323
Fair Value	7,596	8,646
Collateralized mortgage obligations: commercial
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	2,111	4,352
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	12
Fair Value	$ 2,111	$ 4,340