Investment Securities - Additional Information (Detail)	9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) Security	Sep. 30, 2019 USD ($) Security	Dec. 31, 2019 USD ($) Security
Net Investment Income [Line Items]
Securities pledged as collateral	$ 269,526		$ 267,899
Number of securities sold | Security	0	7
Number of securities sold for loss | Security			4
Debt securities realized loss			$ 18,000
Number of securities sold for gain | Security			3
Debt securities realized gain			$ 23,000
Debt securities realized net of gain		$ 5,000	5,000
Held-to-maturity unrealized loss position, fair value			537,000
Unamortized unrealized loss	$ (61,397)		(81,076)
Collateralized Mortgage Backed [Member]
Net Investment Income [Line Items]
Number of securities temporarily impaired and unrealized loss position of less than 12 months	2
Available for sale securities, temporarily impaired and unrealized loss position of less than 12 months, fair value	$ 52,000
Number of securities temporarily impaired and unrealized loss position of more than 12 months	1
Available for sale securities, temporarily impaired and unrealized loss position of more than 12 months, fair value	$ 499,000
U.S Government Agencies [Member]
Net Investment Income [Line Items]
Number of securities temporarily impaired and unrealized loss position of more than 12 months	9
Available for sale securities, temporarily impaired and unrealized loss position of more than 12 months, fair value	$ 6,700,000
Municipal Securities [Member]
Net Investment Income [Line Items]
Number of securities temporarily impaired and unrealized loss position of more than 12 months	3
Available for sale securities, temporarily impaired and unrealized loss position of more than 12 months, fair value	$ 4,300,000
Held-to-maturity unrealized loss position, fair value	$ 0		$ 537,000