Securities - Amortized Cost and Fair Value of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less	$ 103,008
Due after one year through five years	98,401
Due after five years through ten years	69,213
Due after ten years	15,035
Debt securities available-for-sale, maturity, amortized cost	285,657
Debt Securities, Available-for-sale, Amortized Cost	768,427	$ 685,170
Fair Value
Due in one year or less	103,278
Due after one year through five years	100,527
Due after five years through ten years	71,933
Due after ten years	15,759
Debt securities available-for-sale, maturity, fair value	291,497
Debt Securities, Available-for-sale, Fair Value	779,133	680,056
Collateralized mortgage obligations of U.S. government corporations and agencies
Amortized Cost
Debt Securities Available-for-Sale With Maturities	186,879
Debt Securities, Available-for-sale, Amortized Cost	186,879	149,849
Fair Value
Debt Securities Available-for-Sale With Maturities	189,348
Debt Securities, Available-for-sale, Fair Value	189,348	148,659
Residential mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Debt Securities Available-for-Sale With Maturities	22,120
Debt Securities, Available-for-sale, Amortized Cost	22,120	24,564
Fair Value
Debt Securities Available-for-Sale With Maturities	22,418
Debt Securities, Available-for-sale, Fair Value	22,418	24,350
Commercial mortgage-backed securities of U.S. government corporations and agencies
Amortized Cost
Debt Securities Available-for-Sale With Maturities	273,771
Debt Securities, Available-for-sale, Amortized Cost	273,771	251,660
Fair Value
Debt Securities Available-for-Sale With Maturities	275,870
Debt Securities, Available-for-sale, Fair Value	$ 275,870	$ 246,784