Securities - Narrative (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) Security	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of securities	$ 31,300,000	$ 28,600,000
Gross gains realized on sale of securities	171,000	118,000
Gross loss realized on sale of securities	8,000	17,000
Tax expense related to realized gains	55,000	$ 34,000
Carrying value of securities pledged for fiduciary powers	$ 112,800,000		$ 113,100,000
Number of securities temporarily impaired | Security	137
Number of securities temporarily impaired in investment grade | Security	133
Number of securities temporarily impaired in speculative grade | Security	4
Credit losses recognized in prior period earnings	$ 0		0
Investment in FHLB stock	5,200,000		4,700,000
Federal Reserve Bank stock	$ 1,700,000		$ 1,700,000