Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jan. 08, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of shares sold	4,961,626	4,876,677	2,145,738
Per share of common stock	$ 0.01	$ 0.01	$ 10,000
Foreclosed assets	$ 0	$ 0		$ 0
Reorganization Cost And Issuing Of Common Stock Deferred	1,816,000
Other comprehensive income (loss) tax	276,000	0
Unrealized Gain (Loss) Marketable Securities	561,000	142,000
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Annual gross revenue benchmark to qualify as emerging growth company	$ 1,000,000,000
Period for company qualifies as emerging growth company from completion of stock offering	5 years
Charitable Foundation [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of shares contributed			48,767,000
Common Stock [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Bank's employee stock issued			175,528,000
Residential Real Estate [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans in process of foreclosure	$ 56,000	$ 240,000