Securities - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) Bond	Jun. 30, 2016	Jun. 30, 2017 USD ($) Bond	Jun. 30, 2016	Dec. 31, 2016 USD ($) Bond
Schedule of Available-for-sale Securities [Line Items]
Average yields (taxable equivalent) on securities	3.09%	3.08%	3.11%	3.06%
Market value of securities	$ 14,700		$ 14,700		$ 19,100
Securities sold under repurchase agreements	10,786		10,786		18,310	[1]
Company's investment in Federal Home Loan Bank stock	3,700		3,700		1,900
Company's investment in Federal Reserve Bank stock	$ 745		$ 745		$ 580
Municipal Securities
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions | Bond	23		23		39
US Government Agencies
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions | Bond	40		40		37
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions | Bond	1		1		1

[1] Derived from the audited December 31, 2016 Consolidated Financial Statements