Securities - Contractual Maturities of Debt Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 40,399
Due after one year through five years	92,940
Due after five years through ten years	89,580
Due after ten years	21,106
Available-for-Sale Debt Securities With Maturities, Amortized Cost	244,025
Amortized Cost	790,208	$ 737,005
Fair Value
Due in one year or less	40,813
Due after one year through five years	97,643
Due after five years through ten years	91,236
Due after ten years	23,109
Available-for-Sale Debt Securities With Maturities, Fair Value	252,801
Total Available-for-Sale Debt Securities, Fair Value	813,883	770,393
Collateralized mortgage obligations of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities	213,394
Amortized Cost	213,394	202,975
Fair Value
Available-for-Sale Debt Securities With Maturities	217,916
Total Available-for-Sale Debt Securities, Fair Value	217,916	209,296
Residential mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities	64,496
Amortized Cost	64,496	66,960
Fair Value
Available-for-Sale Debt Securities With Maturities	63,911
Total Available-for-Sale Debt Securities, Fair Value	63,911	67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Available-for-Sale Debt Securities With Maturities	266,292
Amortized Cost	266,292	258,875
Fair Value
Available-for-Sale Debt Securities With Maturities	277,253
Total Available-for-Sale Debt Securities, Fair Value	277,253	$ 273,681
Corporate obligations
Amortized Cost
Available-for-Sale Debt Securities With Maturities	2,001
Fair Value
Available-for-Sale Debt Securities With Maturities	$ 2,002