Securities - HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
HTM, Amortized Cost, Rolling Maturities
Due in one year or less	$ 4,947
Due after one year through five years	2,850
Due after five years through ten years	26,721
Due after ten years	61,001
Total	95,519
Amortized cost	368,031	$ 351,831
HTM, Fair Value, Rolling Maturities
Due in one year or less	4,954
Due after one year through five years	2,884
Due after five years through ten years	26,253
Due after ten years	59,825
Total	93,916
Fair Value	364,122	345,088
Residential mortgage-backed Securities
HTM, Amortized Cost, Rolling Maturities
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	16,973
Amortized cost	16,973	19,606
HTM, Fair Value, Rolling Maturities
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	17,171
Fair Value	17,171	19,613
Collateralized mortgage obligations
HTM, Amortized Cost, Rolling Maturities
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	183,926
Amortized cost	183,926	217,954
HTM, Fair Value, Rolling Maturities
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	181,528
Fair Value	181,528	$ 214,710
Commercial mortgage-backed Securities
HTM, Amortized Cost, Rolling Maturities
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	71,613
HTM, Fair Value, Rolling Maturities
Mortgage-backed securities, collateralized mortgage obligations and commercial mortgage-backed securities	$ 71,507