Securities - Narrative (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($) Security	Sep. 30, 2015 USD ($) Security	Dec. 31, 2014 USD ($)
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of securities		$ 82,300,000
Gross gains realized on sale of securities		175,000
Gross loss realized on sale of securities		37,000
Tax expense related to realized gains		47,000
Carrying value of securities pledged for fiduciary powers	$ 109,500,000	$ 109,500,000	$ 125,700,000
Number of securities temporarily impaired | Security	145	145
Number of securities temporarily impaired in investment grade | Security	143	143
Number of securities temporarily impaired in speculative grade | Security	2	2
Credit losses recognized in prior period earnings	$ 0	$ 0	0
Investment in FHLB stock			3,600,000
Federal Reserve Bank stock	$ 1,700,000	$ 1,700,000	$ 1,700,000