Investment Securities - Summary of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized Cost
Available-for-sale: Due after one year through five years	$ 6,389
Available-for-sale: Due after five years through ten years	24,097
Available-for-sale: Due after ten years	18,942
Amortized Cost	434,749	$ 443,928
Fair Value
Available-for-sale: Due after one year through five years	5,888
Available-for-sale: Due after five years through ten years	24,505
Available-for-sale: Due after ten years	19,028
Fair Value	434,679	437,754
Amortized Cost
Held-to-maturity: Due in one year or less	451
Held-to-maturity: Due after one year through five years	1,211
Amortized Cost	35,107	37,759
Fair Value
Held-to-maturity: Due in one year or less	451
Held-to-maturity: Due after one year through five years	1,208
Fair Value	34,834	36,974
Mortgage-backed securities
Amortized Cost
Amortized Cost	385,321	370,706
Fair Value
Fair Value	385,258	365,877
Amortized Cost
Amortized Cost	33,445	35,782
Fair Value
Fair Value	$ 33,175	$ 35,006