Securities - Amortized costs and fair values of securities available for sale (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 367,562	$ 342,233
Gross Unrealized Gains	7,381	8,068
Gross Unrealized Losses	(2,164)	(2,038)
Fair Value	372,779	348,263
U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	67,119	41,317
Gross Unrealized Gains	656	283
Gross Unrealized Losses	(58)	(203)
Fair Value	67,717	41,397
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	50
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	50
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	75,131	55,541
Gross Unrealized Gains	1,908	2,408
Gross Unrealized Losses	(470)	(209)
Fair Value	76,569	57,740
Mortgage-backed securities, Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	137,836	169,257
Gross Unrealized Gains	4,282	4,698
Gross Unrealized Losses	(434)	(742)
Fair Value	141,684	173,213
Mortgage-backed securities, Non-agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,914	28,235
Gross Unrealized Gains	28	115
Gross Unrealized Losses	(60)	(227)
Fair Value	14,882	28,123
Other asset backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	54,958	31,338
Gross Unrealized Gains	505	433
Gross Unrealized Losses	(475)	(58)
Fair Value	54,988	31,713
Corporate securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,554	16,545
Gross Unrealized Gains	2	131
Gross Unrealized Losses	(667)	(599)
Fair Value	$ 16,889	$ 16,077