Securities - AFS Contractual Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
AFS, Amortized Cost, Rolling Maturity
Due in one year or less	$ 6,056
Due after one year through five years	58,432
Due after five years through ten years	20,229
Due after ten years	21,522
Total	106,239
Amortized cost	1,061,096	$ 899,817
AFS, Fair Value, Rolling Maturity
Due in one year or less	6,065
Due after one year through five years	60,042
Due after five years through ten years	20,987
Due after ten years	22,881
Total	109,975
Fair Value	1,091,348	911,493
Residential Mortgage Backed Securities
AFS, Amortized Cost, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	535,874
Amortized cost	535,874	430,514
AFS, Fair Value, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	552,708
Fair Value	552,708	437,029
Collateralized Mortgage Obligations
AFS, Amortized Cost, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	400,298
Amortized cost	400,298	333,256
AFS, Fair Value, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	409,134
Fair Value	409,134	335,616
Commercial mortgage-backed securities
AFS, Amortized Cost, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	18,685
Amortized cost	18,685	11,488
AFS, Fair Value, Rolling Maturity
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	19,531
Fair Value	$ 19,531	$ 12,031