Investment Securities - Narrative (Details)	Sep. 30, 2017 USD ($) security	Dec. 31, 2016 USD ($)
Investments, Debt and Equity Securities [Abstract]
Carrying value of securities pledged as collateral	$ 511,192,000	$ 572,896,000
Book value of securities sold under agreements to repurchase	141,329,000	145,936,000
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale unrealized losses	3,963,000	9,674,000
Held-to-maturity unrealized losses	1,698,000	3,802,000
State and municipal
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale unrealized losses	$ 2,006,000	5,564,000
Available-for-sale, number of securities in unrealized loss positions | security	83
Held-to-maturity unrealized losses	$ 575,000	1,796,000
Held-to-maturity, number of securities in unrealized loss positions | security	31
U.S. Government-sponsored agency securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale unrealized losses	$ 0
Available-for-sale, number of securities in unrealized loss positions | security	0
Held-to-maturity unrealized losses	$ 311,000	479,000
Held-to-maturity, number of securities in unrealized loss positions | security	4
U.S. Government-sponsored mortgage-backed securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale unrealized losses	$ 1,957,000	3,071,000
Available-for-sale, number of securities in unrealized loss positions | security	39
Held-to-maturity unrealized losses	$ 812,000	$ 1,527,000
Held-to-maturity, number of securities in unrealized loss positions | security	23