Securities - Narrative (Details)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($) Security	Sep. 30, 2016 USD ($) Security	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Investments, Debt and Equity Securities [Abstract]
Proceeds from sale of available for sale securities		$ 43,900,000	$ 11,600,000
Proceeds from sales of securities		58,700,000	70,700,000
Gross gains realized on sale of securities		534,000	175,000
Gross loss realized on sale of securities		23,000	37,000
Tax expense related to realized gains		174,000	$ 47,000
Carrying value of securities pledged for fiduciary powers	$ 120,000,000	$ 120,000,000		$ 113,100,000
Number of securities temporarily impaired | Security	141	141
Number of securities temporarily impaired in investment grade | Security	136	136
Number of securities temporarily impaired in speculative grade | Security	5	5
Credit losses recognized in prior period earnings	$ 0	$ 0		0
Investment in FHLB stock	3,900,000	3,900,000		4,700,000
Federal Reserve Bank stock	$ 1,700,000	$ 1,700,000		$ 1,700,000