Investment Securities - Narrative (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) security	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value of investments	$ 510,297,000	$ 177,584,000
Unrealized losses on mortgage-backed securities portfolio	9,674,000	578,000
Unrealized losses in available for sale and held to maturity portfolios	3,802,000	802,000
Carrying value of securities pledged as collateral	572,896,000	637,358,000	$ 449,408,000
Securities sold under repurchase agreements	145,936,000	153,789,000
Gross gains on securities sold	3,389,000	2,770,000	3,581,000
Gross losses from sale of available for sale securities	0	100,000	$ 0
Investments in Debt and Equity Securities, Reported at Less than Historical Cost
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Historical cost	523,773,000	178,964,000
Fair value of investments	$ 510,297,000	$ 177,584,000
Percent of the Corporation's available for sale and held to maturity portfolio	39.10%	13.90%
U.S. Government-Sponsored Mortgage-backed Securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio	$ 3,071,000	$ 518,000
Available-for-sale, number of securities in unrealized loss positions | security	46
Unrealized losses in available for sale and held to maturity portfolios	$ 1,527,000	787,000
Held-to-maturity, number of securities in unrealized loss positions | security	29
State and Municipal Securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio	$ 5,564,000	60,000
Available-for-sale, number of securities in unrealized loss positions | security	108
Unrealized losses in available for sale and held to maturity portfolios	$ 1,796,000	15,000
Held-to-maturity, number of securities in unrealized loss positions | security	71
U.S. Government-sponsored agency securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio	$ 0
Available-for-sale, number of securities in unrealized loss positions | security	0
Unrealized losses in available for sale and held to maturity portfolios	$ 479,000
Held-to-maturity, number of securities in unrealized loss positions | security	4
Equity securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio	$ 1,039,000
Available-for-sale, number of securities in unrealized loss positions | security	1
Unrealized losses in available for sale and held to maturity portfolios	$ 0
Held-to-maturity, number of securities in unrealized loss positions | security	0