Investment Securities - Summary of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized Cost
Available-for-sale: Due in one year or less	$ 1,139
Available-for-sale: Due after one year through five years	8,265
Available-for-sale: Due after five years through ten years	53,450
Available-for-sale: Due after ten years	282,619
Available-for-sale, Amortized Cost	345,473
Fair Value
Available-for-sale: Due in one year or less	1,142
Available-for-sale: Due after one year through five years	8,484
Available-for-sale: Due after five years through ten years	55,145
Available-for-sale: Due after ten years	281,732
Available-for-sale, Fair Value	346,503
Amortized Cost
Held-to-maturity: Due in one year or less	1,235
Held-to-maturity: Due after one year through five years	5,633
Held-to-maturity: Due after five years through ten years	42,646
Held-to-maturity: Due after ten years	37,948
Held-to-maturity, Amortized Cost	87,462	$ 98,211
Fair Value
Held-to-maturity: Due in one year or less	1,236
Held-to-maturity: Due after one year through five years	5,699
Held-to-maturity: Due after five years through ten years	43,368
Held-to-maturity: Due after ten years	38,157
Held-to-maturity, Fair Value	$ 88,460	$ 98,261