Investment Securities - Amortized cost and estimated fair value by contractual maturity of debt securities (Details 1) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available-for-Sale Amortized Cost
Due in one year or less
Due after one year through five years	9,609
Due after five years through ten years
Due after ten years	1,000
Sub-total	10,609
Amortized cost	18,494	$ 17,875
Available-for-Sale Fair Value
Due in one year or less
Due after one year through five years	9,543
Due after five years through ten years
Due after ten years	986
Sub-total	10,529
Fair Value	18,395	17,747
Held-to-Maturity Amortized Cost
Due in one year or less	1,000
Due after one year through five years	3,536
Due after five years through ten years	1,407
Due after ten years
Sub-total	5,943
Amortized cost	6,598	7,420
Held-to-Maturity Fair Value
Due in one year or less	1,002
Due after one year through five years	3,549
Due after five years through ten years	1,430
Due after ten years
Sub-total	5,981
Fair Value	6,644	7,384
Mortgage-backed securities - residential
Available-for-Sale Amortized Cost
Amortized cost	7,885	9,769
Available-for-Sale Fair Value
Fair Value	7,866	9,748
Held-to-Maturity Amortized Cost
Amortized cost	655	745
Held-to-Maturity Fair Value
Fair Value	$ 663	$ 758