Securities - Amortized costs and fair values of securities available for sale (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 303,490	$ 371,733
Gross Unrealized Gains	2,251	5,798
Gross Unrealized Losses	(4,174)	(2,960)
Fair Value	301,567	374,571
U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	73,546	79,005
Gross Unrealized Gains	209	315
Gross Unrealized Losses	(571)	(380)
Fair Value	73,184	78,940
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	62,896	74,071
Gross Unrealized Gains	1,019	1,956
Gross Unrealized Losses	(542)	(434)
Fair Value	63,373	75,593
Mortgage-backed securities, Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	98,549	129,360
Gross Unrealized Gains	646	3,046
Gross Unrealized Losses	(1,144)	(745)
Fair Value	98,051	131,661
Mortgage-backed securities, Non-agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,991	12,782
Gross Unrealized Gains	16	33
Gross Unrealized Losses	(74)	(38)
Fair Value	9,933	12,777
Other Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,860	58,958
Gross Unrealized Gains	361	426
Gross Unrealized Losses	(616)	(603)
Fair Value	41,605	58,781
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,648	17,557
Gross Unrealized Gains	0	22
Gross Unrealized Losses	(1,227)	(760)
Fair Value	$ 15,421	$ 16,819