Securities - Amortized costs and fair values of securities available for sale (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 341,257	$ 371,733
Gross Unrealized Gains	8,177	5,798
Gross Unrealized Losses	(2,251)	(2,960)
Fair Value	347,183	374,571
U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	65,442	79,005
Gross Unrealized Gains	1,216	315
Gross Unrealized Losses	(127)	(380)
Fair Value	66,531	78,940
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	67,664	74,071
Gross Unrealized Gains	2,420	1,956
Gross Unrealized Losses	(89)	(434)
Fair Value	69,995	75,593
Mortgage-backed securities, Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	123,514	129,360
Gross Unrealized Gains	3,826	3,046
Gross Unrealized Losses	(550)	(745)
Fair Value	126,790	131,661
Mortgage-backed securities, Non-agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,306	12,782
Gross Unrealized Gains	131	33
Gross Unrealized Losses	(40)	(38)
Fair Value	13,397	12,777
Other asset backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	54,725	58,958
Gross Unrealized Gains	525	426
Gross Unrealized Losses	(744)	(603)
Fair Value	54,506	58,781
Corporate securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,606	17,557
Gross Unrealized Gains	59	22
Gross Unrealized Losses	(701)	(760)
Fair Value	$ 15,964	$ 16,819