Securities - Amortized costs and fair values of securities held to maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	$ 1,500	$ 1,500
Gross unrealized gains	0
Gross unrealized losses	(125)
Fair value	1,375	1,397
Obligations of states and political subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	1,500	1,500
Gross unrealized gains	0	0
Gross unrealized losses	(125)	(103)
Fair value	$ 1,375	$ 1,397