Securities - Amortized Cost and Fair Value of Securities Held to Maturity by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost
Amortized Cost	$ 15,778	$ 9,200
Estimated Fair Value
Securities held to maturity	16,416	9,293
U.S. Government agencies
Amortized Cost
Due after one year through five years	5,000	5,000
Amortized Cost	5,000	5,000
Estimated Fair Value
Due after one year through five years	5,018	5,046
Securities held to maturity	5,018	5,046
Municipals
Amortized Cost
Due after one year through five years	1,996	2,028
Due after five years through ten years	1,609	1,617
Due after ten years through fifteen years	553	555
Due after fifteen years	6,620	0
Amortized Cost	10,778	4,200
Estimated Fair Value
Due after one year through five years	2,032	2,062
Due after five years through ten years	1,637	1,649
Due after ten years through fifteen years	530	536
Due after fifteen years	7,199	0
Securities held to maturity	$ 11,398	$ 4,247