Securities - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($) Securities	Sep. 30, 2017 USD ($) Securities	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Fair value of pledged securities	$ 101,000	$ 101,000		$ 95,000
Restricted stock investment in FHLB stock	4,100	4,100		4,100
Federal Reserve Bank stock	471	471		$ 471
Proceeds from sales of securities	$ 0	$ 0	$ 1
Number of securities in an unrealized loss position, Total | Securities	46	46
Number of securities in continuous unrealized loss position, 12 months or more | Securities		20
Restricted Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Gain on conversion of stock			$ 1