Benefit Plans - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Installment	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2017 USD ($)
Accumulated other comprehensive income (loss), defined benefit plan, after tax total	$ 506,001	$ 577,698
Prior service cost	400,535	506,534
Net actuarial loss	105,466	71,164
Deferred income tax recorded in accumulated other comprehensive loss	142,235	162,391
Unrecognized past service liability	$ 116,377	118,515
Percentage of monthly retirement benefit changed from directors	100.00%
Percentage of three year average annual compensation paid	15.00%
Number of equal installments average compensation paid | Installment	12
Average annual compensation payment period	120 months
Defined benefit plan, benefit obligation	$ 2,108,344	2,001,330		$ 1,971,177
Defined benefit plan, expense	116,224	108,787
Defined benefit plan amount recognized in accumulated other comprehensive loss	$ 85,960	89,286
Minimum
Director's average annual retainer period	3 years
Maximum
Period served by director on board	120 months
Scenario Forecast
Prior service cost			$ 123,945
Defined benefit plan, expected future employer contributions, next fiscal year			$ 104,642
Directors Retirement Plan
Percentage of average annual retainer percent	100.00%
Annual retainer period of payment	3 years
401 (k) Retirement Plan
Discretionary employer contributions, percent of match	100.00%
Defined contribution plan, maximum annual contributions per employee, percent	6.00%
Defined contribution plan, safe harbor contribution percentage	3.00%
Discretionary employer contributions	$ 267,000	214,000
SERP
Defined benefit plan, benefit obligation	$ 520,694	$ 407,796