Securities - Contractual Maturities of Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less	$ 41,497
Due after one year through five years	111,446
Due after five years through ten years	38,856
Due after ten years	26,355
Debt Securities Available-for-sale, Maturity, Amortized Cost	218,154
Debt Securities, Available-for-Sale, Amortized Cost	679,473	$ 768,427
Fair Value
Due in one year or less	42,069
Due after one year through five years	117,923
Due after five years through ten years	41,458
Due after ten years	28,835
Debt Securities Available-for-sale, Maturity, Fair Value	230,285
Debt Securities, Available-for-Sale, Fair Value	714,920	779,133
Collateralized mortgage obligations of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities	175,516
Debt Securities, Available-for-Sale, Amortized Cost	175,516	186,879
Fair Value
Available-for-Sale Debt Securities With Maturities	183,032
Debt Securities, Available-for-Sale, Fair Value	183,032	189,348
Residential mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities	16,578
Debt Securities, Available-for-Sale, Amortized Cost	16,578	22,120
Fair Value
Available-for-Sale Debt Securities With Maturities	17,352
Debt Securities, Available-for-Sale, Fair Value	17,352	22,418
Commercial mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities	265,202
Debt Securities, Available-for-Sale, Amortized Cost	265,202	273,771
Fair Value
Available-for-Sale Debt Securities With Maturities	280,224
Debt Securities, Available-for-Sale, Fair Value	280,224	$ 275,870
Corporate Securities
Amortized Cost
Available-for-Sale Debt Securities With Maturities	4,023
Fair Value
Available-for-Sale Debt Securities With Maturities	$ 4,027