Compensation and Benefit Plans - Additional Information (Detail) $ / shares in Units, $ in Thousands		3 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2020 USD ($) Executive $ / shares shares		Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares		Sep. 30, 2019 USD ($)	Dec. 31, 2019 $ / shares shares		May 06, 2029 shares	Dec. 31, 2018 $ / shares
Compensation And Benefit Plans Disclosure [Line Items]
Maximum employer matching contribution percentage					4.00%
Employer matching contribution percentage					3.00%
Expenses recognized | $		$ 103		$ 89	$ 474		$ 256
ESOP related compensation expense including equalization expense | $		115		184	$ 402		574
Number of option grants					40,000			8,918
Total remaining unrecognized compensation cost | $		$ 519			$ 519
Weighted average period expected to be recognized					87 months
Weighted-average exercise price for options | $ / shares		$ 12.02	[1]		$ 12.02	[1]		$ 12.78	[1]		$ 12.77
Weighted average remaining contractual life					8 years 1 month 6 days
Weighted average period expected to be recognized					5 years
Number of shares exercisable	[1]	24,788			24,788			24,788
Stock repurchase program, number of shares repurchase					1,346,679
2018 Long-Term Incentive Plan
Compensation And Benefit Plans Disclosure [Line Items]
Equity incentive plans, maximum number of shares issuable		1,248,469			1,248,469
Common stock reserved for future issuance		1,248,469			1,248,469
Conversion of issuable stock options to issuable restricted stock ratio					3.0
Number of issuable stock options converted into restricted stock units					462,522
Number of restricted stock units converted from issuable stock options					154,174
Number of grants					674,645
Conversion of issuable stock options to issuable restricted stock		60,159			60,159			88,492
Stock repurchase program, number of shares repurchase					1,436,814
Stock repurchase program, weighted average price per share | $ / shares					$ 13.62
2018 Long-Term Incentive Plan | Executive Officers
Compensation And Benefit Plans Disclosure [Line Items]
Vesting percentage					20.00%
2018 Long-Term Incentive Plan | Directors
Compensation And Benefit Plans Disclosure [Line Items]
Vesting percentage					20.00%
Vesting period					10 years
2020 Long-Term Incentive Plan
Compensation And Benefit Plans Disclosure [Line Items]
Number of issuable stock options converted into restricted stock units					45,000
Number of restricted stock units converted from issuable stock options					15,000
Stock Options or Stock Appreciation Rights | 2018 Long-Term Incentive Plan
Compensation And Benefit Plans Disclosure [Line Items]
Common stock reserved for future issuance		891,764			891,764
Shares available for future awards		180,476			180,476			265,476
Restricted Stock Units
Compensation And Benefit Plans Disclosure [Line Items]
Number of stock grants					15,000			29,725
Compensation expense | $		$ 319		314	$ 956		923
Total remaining unrecognized compensation cost | $		$ 4,477			$ 4,477
Weighted average period expected to be recognized					87 months
Restricted Stock Units | 2018 Long-Term Incentive Plan
Compensation And Benefit Plans Disclosure [Line Items]
Common stock reserved for future issuance		356,705			356,705
Shares available for future awards		0			0					0
Restricted Stock Units | 2018 Long-Term Incentive Plan | Executive Officers
Compensation And Benefit Plans Disclosure [Line Items]
Number of stock grants					322,254
Restricted Stock Units | 2018 Long-Term Incentive Plan | Outside Directors
Compensation And Benefit Plans Disclosure [Line Items]
Number of stock grants					148,625
Restricted Stock Units | 2018 Long-Term Incentive Plan | Non-Executive Officers
Compensation And Benefit Plans Disclosure [Line Items]
Number of stock grants					40,000
Restricted Stock Units | 2018 Long-Term Incentive Plan | Non-Executive Officers | September 30, 2020
Compensation And Benefit Plans Disclosure [Line Items]
Number of stock grants					15,000
Restricted Stock Units | 2018 Long-Term Incentive Plan | Directors
Compensation And Benefit Plans Disclosure [Line Items]
Stock repurchase program, shares reissued of restricted stock units					90,135
Incentive Options | 2018 Long-Term Incentive Plan | Executive Officers
Compensation And Benefit Plans Disclosure [Line Items]
Number of option grants					119,176
Incentive Options | 2018 Long-Term Incentive Plan | Non-Executive Officers | September 30, 2020
Compensation And Benefit Plans Disclosure [Line Items]
Number of stock grants					40,000
Non-qualified Options | 2018 Long-Term Incentive Plan | Outside Directors
Compensation And Benefit Plans Disclosure [Line Items]
Number of option grants					44,590
Stock Options
Compensation And Benefit Plans Disclosure [Line Items]
Compensation expense | $		$ 33		29	$ 93		$ 77
Weighted average period expected to be recognized					6 years 6 months		6 years 6 months
Supplemental Executive Retirement Plan
Compensation And Benefit Plans Disclosure [Line Items]
Number of key executive under retirement plan | Executive		1
Expense recognized | $		$ 15		$ 12	$ 45		$ 45
Employee Stock Ownership Plan
Compensation And Benefit Plans Disclosure [Line Items]
ESOP borrowed amount | $		$ 7,238			$ 7,238
Number of ESOP shares purchased					723,751
ESOP shares purchased expressed as percentage of common stock issued in stock offering					3.92%
Expected period of loan repaid					15 years

[1] The aggregate intrinsic value, which represents the difference between the price of the Company’s common stock at respective periods and the stated exercise price of the underlying options, was $0 and $315 for outstanding options and $0 and $48 for exercisable options at September 30, 2020 and December 31, 2019, respectively.