Investment Securities - Narrative (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) security	Mar. 31, 2017 USD ($) security	Dec. 31, 2017 USD ($)
Investments, Debt and Equity Securities [Abstract]
Number of private-label collateralized mortgage obligations | security	1
Combined balance of private-label collateralized mortgage obligations	$ 7,000
AFS and HTM securities in unrealized loss positions qualitative disclosure number of positions | security	106
Unrealized losses as a percentage of individual securities amortized cost basis	3.17%
Unrealized losses as percentage of Company's total amortized cost basis	2.63%
Number of securities in an unrealized loss position for over 12 months | security	45
Amortized cost basis of securities in a continuous loss position	$ 169,100,000
Unrealized loss on securities in a continuous loss position	7,200,000
Impairment related to credit quality	$ 0
Number of Available for sale Securities Sold | security	1	10
Number Of Held to Maturity Securities Sold | security		1
Available-for-sale securities, realized gain (loss)	$ 0	$ 1,000
Held-to-maturity Securities, Sold Security, Realized Gain (Loss)		$ 7,000
Number of available-for-sale securities sold with gains | security		7
Available-for-sale securities, gross realized gains		$ 108,000
Number of available-for-sale securities sold with losses | security		3
Available-for-sale securities, gross realized losses		$ 109,000
Securities pledged as collateral for public funding	$ 187,000,000		$ 177,900,000