Investment securities Investment Securities Held-to-Maturity Gross Unrealized Losses (Details) - State and political subdivisions [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Continuous unrealized loss position, less than 12 months, fair value	$ 2,832	$ 13,048
Continuous unrealized loss position, less than 12 months, gross unrealized losses	(42)	(186)
Continuous unrealized loss position, 12 months or longer, fair value	7,341	0
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	(182)	0
Total, continuous unrealized loss position, fair value	10,173	13,048
Total, continuous unrealized loss position, gross unrealized losses	$ (224)	$ (186)