Fair Value - Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurement Recurring - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	$ 27,144	$ 28,897
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	4,995
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	22,149	28,897
U.S. Government and Federal Agencies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	20,515	24,552
U.S. Government and Federal Agencies | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	20,515	24,552
U S Treasury
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	4,995
U S Treasury | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	4,995
FNMA Certificates
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	759	1,103
FNMA Certificates | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	759	1,103
GNMA Certificates
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	875	3,242
GNMA Certificates | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities measure at fair value on recurring basis	$ 875	$ 3,242