Fair Value Measurements - Summary of Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Financial assets
Cash and due from banks	$ 508,069	$ 114,342	$ 55,395	$ 78,705
Securities available for sale	39,723	28,555
Loans, net	1,288,088	940,944
Accrued interest receivable	7,379	3,398
Financial liabilities
Deposits	1,385,982	991,631
Other borrowings	364,703	10,032
Subordinated debt	5,063	5,112
Accrued interest payable	403	400
Carrying Amount [Member]
Financial assets
Cash and due from banks	508,069	114,342
Securities available for sale	39,723	28,555
Loans, net	1,285,388	941,132
Accrued interest receivable	7,379	3,398
Financial liabilities
Deposits	1,385,702	988,236
Other borrowings	364,703	10,000
Subordinated debt	4,986	4,977
Accrued interest payable	402	400
Level 1 [Member]
Financial assets
Cash and due from banks	508,069	114,342
Financial liabilities
Deposits	1,221,207	870,495
Level 2 [Member]
Financial assets
Securities available for sale	39,723	28,555
Accrued interest receivable	106	168
Financial liabilities
Deposits	164,775	121,136
Accrued interest payable	107	326
Level 3 [Member]
Financial assets
Loans, net	1,288,088	940,944
Accrued interest receivable	7,273	3,230
Financial liabilities
Other borrowings	364,703	10,032
Subordinated debt	5,063	5,112
Accrued interest payable	$ 296	$ 74