Securities - AFS Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
AFS, Amortized Cost, Rolling Maturity
Due in one year or less	$ 2,071
Due after one year through five years	73,668
Due after five years through ten years	35,387
Due after ten years	21,786
Total	132,912
Amortized cost	945,156	$ 899,817
AFS, Fair Value, Rolling Maturity
Due in one year or less	2,090
Due after one year through five years	75,246
Due after five years through ten years	35,914
Due after ten years	22,845
Total	136,095
Fair Value	972,318	911,493
Residential Mortgage Backed Securities
AFS, Amortized Cost, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	415,399
Amortized cost	415,399	430,514
AFS, Fair Value, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	429,834
Fair Value	429,834	437,029
Collateralized Mortgage Obligations
AFS, Amortized Cost, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	385,409
Amortized cost	385,409	333,256
AFS, Fair Value, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	393,986
Fair Value	393,986	335,616
Commercial mortgage-backed securities
AFS, Amortized Cost, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	11,436
Amortized cost	11,436	11,488
AFS, Fair Value, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	12,403
Fair Value	$ 12,403	$ 12,031