Securities - Amortized costs and fair values of securities available for sale (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 347,925	$ 371,733
Gross Unrealized Gains	6,882	5,798
Gross Unrealized Losses	(2,189)	(2,960)
Fair Value	352,618	374,571
U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	69,635	79,005
Gross Unrealized Gains	827	315
Gross Unrealized Losses	(163)	(380)
Fair Value	70,299	78,940
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	66,146	74,071
Gross Unrealized Gains	2,055	1,956
Gross Unrealized Losses	(103)	(434)
Fair Value	68,098	75,593
Mortgage-backed securities, Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	131,134	129,360
Gross Unrealized Gains	3,267	3,046
Gross Unrealized Losses	(513)	(745)
Fair Value	133,888	131,661
Mortgage-backed securities, Non-agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,273	12,782
Gross Unrealized Gains	43	33
Gross Unrealized Losses	(94)	(38)
Fair Value	11,222	12,777
Other asset backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	53,085	58,958
Gross Unrealized Gains	652	426
Gross Unrealized Losses	(465)	(603)
Fair Value	53,272	58,781
Corporate securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,652	17,557
Gross Unrealized Gains	38	22
Gross Unrealized Losses	(851)	(760)
Fair Value	$ 15,839	$ 16,819