Securities - Additional Information (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($)
Investments, Debt and Equity Securities [Abstract]
FHLB stock requirement, percentage of outstanding capital	3.00%
FHLB stock requirement, percentage subject to call	3.00%
FHLB stock requirement, percentage of outstanding borrowings	4.25%
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment losses recognized | $	$ 0	$ 0
Federal agencies and GSEs
Schedule of Available-for-sale Securities [Line Items]
Number of securities with unrealized losses	23
Number of securities in unrealized loss position for 12 months or more	12
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Number of securities with unrealized losses	65
Number of securities in unrealized loss position for 12 months or more	16
Collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Number of securities with unrealized losses	2
Number of securities in unrealized loss position for 12 months or more	1
State and municipal securities
Schedule of Available-for-sale Securities [Line Items]
Number of securities with unrealized losses	60
Number of securities in unrealized loss position for 12 months or more	11
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Number of securities with unrealized losses	2