Investment Securities - Summary of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Amortized Cost
Available-for-sale: Due after one year through five years	$ 3,300
Available-for-sale: Due after five years through ten years	13,236
Available-for-sale: Due after ten years	9,132
Amortized Cost	421,482	$ 443,928
Fair Value
Available-for-sale: Due after one year through five years	2,333
Available-for-sale: Due after five years through ten years	13,622
Available-for-sale: Due after ten years	9,604
Fair Value	425,638	437,754
Amortized Cost
Held-to-maturity: Due in one year or less	766
Held-to-maturity: Due after one year through five years	893
Amortized Cost	33,219	37,759
Fair Value
Held-to-maturity: Due in one year or less	767
Held-to-maturity: Due after one year through five years	895
Fair Value	33,363	36,974
Mortgage-backed securities
Amortized Cost
Amortized Cost	395,814	370,706
Fair Value
Fair Value	400,079	365,877
Amortized Cost
Amortized Cost	31,560	35,782
Fair Value
Fair Value	$ 31,701	$ 35,006