Income Taxes - Sources of Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Organizational and start-up costs	$ 38	$ 51
Allowance for loan losses	11,679	5,881
Unrealized loss on securities	0	5,427
Net operating loss carry forward	1,753	2,035
Purchase accounting fair value adjustments	565	594
Accrued other expenses	1,284	701
Nonaccrual loan interest	110	105
Loan fees	1,050	656
Cash flow hedge	416	0
Lease liability	11,565	0
Other	1,652	1,421
Total deferred tax asset	30,112	16,871
Deferred tax liabilities:
Mortgage servicing rights	(841)	(879)
Premises and equipment	(1,620)	(1,204)
Prepaid expenses	(431)	(702)
Lease right-of-use asset	(11,085)	0
Unrealized gain on securities	(907)	0
Other	(999)	(897)
Total deferred tax liability	(15,883)	(3,682)
Net deferred tax asset	$ 14,229	$ 13,189