Securities - Contractual Maturities of Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 30,428
Due after one year through five years	82,551
Due after five years through ten years	101,252
Due after ten years	20,936
Available-for-Sale Debt Securities With Maturities, Amortized Cost	235,167
Amortized Cost	850,672	$ 737,005
Fair Value
Due in one year or less	30,760
Due after one year through five years	86,321
Due after five years through ten years	102,563
Due after ten years	22,917
Available-for-Sale Debt Securities With Maturities, Fair Value	242,561
Total Available-for-Sale Debt Securities, Fair Value	868,994	770,393
Collateralized mortgage obligations of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Fixed Maturities	206,325
Amortized Cost	206,325	202,975
Fair Value
Available-for-Sale Debt Securities With Fixed Maturities	208,985
Total Available-for-Sale Debt Securities, Fair Value	208,985	209,296
Residential mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Fixed Maturities	60,855
Amortized Cost	60,855	66,960
Fair Value
Available-for-Sale Debt Securities With Fixed Maturities	60,442
Total Available-for-Sale Debt Securities, Fair Value	60,442	67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Fixed Maturities	347,825
Amortized Cost	347,825	258,875
Fair Value
Available-for-Sale Debt Securities With Fixed Maturities	356,506
Total Available-for-Sale Debt Securities, Fair Value	356,506	$ 273,681
Corporate bonds
Amortized Cost
Available-for-Sale Debt Securities With Fixed Maturities	500
Fair Value
Available-for-Sale Debt Securities With Fixed Maturities	$ 500