Categories of Loan (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Accounts Notes And Loans Receivable [Line Items]
Commercial loans	$ 57,478		$ 52,286
Commercial real estate	152,264		158,314
Residential real estate	82,857		83,870
Installment loans	19,323		21,284
Total gross loans	311,922		315,754
Less allowance for loan losses	(2,697)	$ (2,506)	(2,400)	$ (3,132)	$ (3,038)	$ (2,894)
Total loans	$ 309,225		$ 313,354