Securities - Amortized costs and fair values of securities available for sale (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 372,310	$ 371,733
Gross Unrealized Gains	7,538	5,798
Gross Unrealized Losses	(2,823)	(2,960)
Fair Value	377,025	374,571
U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	79,817	79,005
Gross Unrealized Gains	1,062	315
Gross Unrealized Losses	(93)	(380)
Fair Value	80,786	78,940
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	68,920	74,071
Gross Unrealized Gains	2,021	1,956
Gross Unrealized Losses	(355)	(434)
Fair Value	70,586	75,593
Mortgage-backed securities, Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	135,239	129,360
Gross Unrealized Gains	3,940	3,046
Gross Unrealized Losses	(621)	(745)
Fair Value	138,558	131,661
Mortgage-backed securities, Non-agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,062	12,782
Gross Unrealized Gains	94	33
Gross Unrealized Losses	(59)	(38)
Fair Value	12,097	12,777
Other asset backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	59,584	58,958
Gross Unrealized Gains	405	426
Gross Unrealized Losses	(893)	(603)
Fair Value	59,096	58,781
Corporate securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,688	17,557
Gross Unrealized Gains	16	22
Gross Unrealized Losses	(802)	(760)
Fair Value	$ 15,902	$ 16,819