Investment Securities - Schedule of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Amortized cost, Due in one year or less	$ 2,036	$ 9,290
Amortized cost, Due in one to five years	27,722	25,520
Amortized cost, Due in five to ten years	17,362	31,122
Amortized cost, Due in over ten years	67,672	62,909
Amortized cost, Total	114,792	128,841
Total debt securities, Amortized cost	537,966	579,715
Fair value, Due in one year or less	2,037	9,352
Fair value, Due in one to five years	28,535	26,340
Fair value, Due in five to ten years	17,851	32,248
Fair value, Due in over ten years	68,338	61,725
Fair value, Total	116,761	129,665
Total debt securities, Fair value	535,555	573,573
Mortgage-backed Securities - Residential
Schedule Of Available For Sale Securities [Line Items]
Total debt securities, Amortized cost	423,174	450,874
Total debt securities, Fair value	$ 418,794	$ 443,908