Securities - Amortized Cost and Fair Value of Securities Available for Sale by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost
Total	$ 396,896	$ 196,504
Estimated Fair Value
Total	395,040	194,090
U.S. Government agencies
Amortized Cost
Due in one year or less	50	0
Due after one year through five years	5,165	5,106
Due after ten years through fifteen years	7,049	0
Due after fifteen years	13,998	0
Estimated Fair Value
Due in one year or less	50	0
Due after one year through five years	5,140	4,994
Due after ten years through fifteen years	6,945	0
Due after fifteen years	13,924	0
Municipals
Amortized Cost
Due in one year or less	691	0
Due after one year through five years	7,788	3,442
Due after one year through five years	8,693	5,025
Due after ten years through fifteen years	26,234	20,463
Due after fifteen years	57,631	16,462
Estimated Fair Value
Due in one year or less	698	0
Due after one year through five years	7,714	3,500
Due after one year through five years	8,657	4,888
Due after ten years through fifteen years	26,629	20,300
Due after fifteen years	57,711	15,671
Mortgage backed securities
Amortized Cost
Due after one year through five years	53,961	24,959
Due after one year through five years	89,120	24,996
Due after ten years through fifteen years	7,433	12,861
Due after fifteen years	98,188	57,978
Estimated Fair Value
Due after one year through five years	54,058	24,916
Due after one year through five years	88,501	24,895
Due after ten years through fifteen years	7,292	12,555
Due after fifteen years	97,064	57,441
Asset backed securities
Amortized Cost
Due after one year through five years	3,067	3,080
Due after fifteen years	5,825	10,025
Estimated Fair Value
Due after one year through five years	3,071	3,001
Due after fifteen years	5,652	9,863
Corporate Bond Securities
Amortized Cost
Due in one year or less	4,001	4,141
Due after one year through five years	4,526	4,490
Estimated Fair Value
Due in one year or less	4,000	4,144
Due after one year through five years	4,551	4,522
Certificates of deposit
Amortized Cost
Due after one year through five years	1,976	1,976
Estimated Fair Value
Due after one year through five years	1,993	2,009
CRA mutual fund
Amortized Cost
CRA mutual fund	1,500	1,500
Estimated Fair Value
CRA mutual fund	$ 1,390	$ 1,391