Equity Incentive Plan - Summary of Company's Outstanding Restricted Stock (Detail) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) $ / shares shares
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		72,071
Expected future remaining compensation expense | $	$ 992	$ 992
Expected future compensation expense, restricted shares remaining vesting period		2 years 6 months 18 days
Restricted Shares Awarded on March 20, 2017 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		1,198
Date of Award		Mar. 20, 2017
Expected future remaining compensation expense | $	6	$ 6
Expected future compensation expense, restricted shares remaining vesting period		3 months
Restricted Shares Awarded on April 10, 2018 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		3,114
Date of Award		Apr. 10, 2018
Expected future remaining compensation expense | $	41	$ 41
Expected future compensation expense, restricted shares remaining vesting period		1 year 3 months
Restricted Shares Awarded on March 14, 2019 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		3,401
Date of Award		Mar. 14, 2019
Expected future remaining compensation expense | $	16	$ 16
Expected future compensation expense, restricted shares remaining vesting period		3 months
Restricted Shares Awarded on March 14, 2019 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		6,560
Date of Award		Mar. 14, 2019
Expected future remaining compensation expense | $	89	$ 89
Expected future compensation expense, restricted shares remaining vesting period		2 years 3 months
Restricted Shares Awarded on March 14, 2020 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		9,139
Date of Award		Mar. 14, 2020
Expected future remaining compensation expense | $	114	$ 114
Expected future compensation expense, restricted shares remaining vesting period		1 year 3 months
Restricted Shares Awarded on March 14, 2019 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		10,390
Date of Award		Mar. 14, 2020
Expected future remaining compensation expense | $	160	$ 160
Expected future compensation expense, restricted shares remaining vesting period		3 years 3 months
Restricted Shares Awarded on March 3, 2021 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		16,277
Date of Award		Mar. 03, 2021
Expected future remaining compensation expense | $	243	$ 243
Expected future compensation expense, restricted shares remaining vesting period		4 years 3 months
Restricted Shares Awarded on March 3, 2021 [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Granted		21,992
Date of Award		Mar. 03, 2021
Expected future remaining compensation expense | $	$ 323	$ 323
Expected future compensation expense, restricted shares remaining vesting period		2 years 3 months
Restricted Stock [Member]
Schedule Of Nonvested Stock Option Activity [Line Items]
Number of Restricted Shares, Nonvested at beginning of period	72,071	54,274
Number of Restricted Shares, Granted	0	39,139
Number of Restricted Shares, Vested	0	(20,275)
Number of Restricted Shares, Forfeited	0	(1,067)
Number of Restricted Shares, Nonvested at end of period	72,071	72,071
Weighted Average Grant Date Fair Value, Nonvested at beginning of period | $ / shares	$ 20.13	$ 20.90
Weighted Average Grant Date Fair Value, Granted | $ / shares	0	19.17
Weighted Average Grant Date Fair Value, Vested | $ / shares	0	20.35
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	0	19.56
Weighted Average Grant Date Fair Value, Nonvested at end of period | $ / shares	$ 20.13	$ 20.13