Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Commitments And Contingencies [Line Items]
Reserve for off-balance sheet credits	$ 426	$ 390
Reserve for sold mortgages	299
Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Reserve for off-balance sheet credits	$ 289
Minimum [Member]
Commitments And Contingencies [Line Items]
Term of letter of credit	1 year
Maximum [Member]
Commitments And Contingencies [Line Items]
Term of letter of credit	5 years
Maximum [Member] | Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Off-balance Sheet Risks, Amount, Liability	$ 61,200