Summary of Significant Accounting Policies - Summary of Bank's Actual Capital Amounts and Ratios, and the Regulatory Minimum Ratios (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounting Policies [Abstract]
Regulatory, Minimum, Common equity tier 1 capital	$ 0
Regulatory, Minimum, Tier 1 capital	0
Regulatory, Minimum, Total capital	0
Regulatory, Minimum, Average assets	0
Regulatory, Minimum, Risk-weighted assets	$ 0
Regulatory, Minimum, Leverage ratio	4.0
Regulatory, Minimum, Common equity tier 1 capital ratio	7.00%
Regulatory, Minimum, Tier 1 capital ratio	8.5
Regulatory, Minimum, Total capital ratio	10.5
Regulatory, Well-Capitalized, Common equity tier 1 capital	$ 0
Regulatory, Well-Capitalized, Tier 1 capital	0
Regulatory, Well-Capitalized, Total capital	0
Regulatory, Well-Capitalized, Average assets	0
Regulatory, Well-Capitalized, Risk-weighted assets	$ 0
Regulatory, Well-Capitalized, Leverage ratio	5.0
Regulatory, Well-Capitalized, Common equity tier 1 capital ratio	6.50%
Regulatory, Well-Capitalized, Tier 1 capital ratio	8.0
Regulatory, Well-Capitalized, Total capital ratio	10.0
Common equity tier 1 capital	$ 148,507	$ 158,187
Tier 1 capital	217,295	226,975
Total capital	233,460	241,842
Average assets	1,283,664	1,172,866
Risk-weighted assets	$ 1,243,783	$ 1,144,337
Leverage ratio	16.9	19.4
Common equity Tier 1 capital ratio	11.9	13.8
Tier 1 capital ratio	17.5	19.8
Total capital ratio	18.8	21.1