Investment Securities - Portfolio of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	$ 73,255	$ 81,052
Gross Unrealized Gains	162	436
Gross Unrealized Losses	1,110	568
Fair Value	72,307	80,920
Obligations of state and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	30,550	35,908
Gross Unrealized Gains	162	265
Gross Unrealized Losses	113	22
Fair Value	30,599	36,151
GSE mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	33,930	35,751
Gross Unrealized Gains	0	171
Gross Unrealized Losses	598	219
Fair Value	33,332	35,703
Collateralized mortgage obligations: residential
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	7,120	7,450
Gross Unrealized Gains	0	0
Gross Unrealized Losses	387	321
Fair Value	6,733	7,129
Collateralized mortgage obligations: commercial
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	1,655	1,943
Gross Unrealized Gains	0	0
Gross Unrealized Losses	12	6
Fair Value	$ 1,643	$ 1,937