Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State tax, net of federal tax benefit	3.70%	3.50%	3.10%
Adjustment to net deferred tax asset for enacted changes in tax laws and rates	(1.20%)	0.00%	(0.50%)
Tax-exempt interest	(0.70%)	(0.60%)	(0.80%)
Bank-owned life insurance income	(0.20%)	(0.10%)	0.00%
Excess tax benefits from share-based compensation	0.00%	(1.00%)	(1.80%)
Nondeductible acquisition costs	0.00%	0.20%	0.40%
Federal tax credits, net of amortization	(0.80%)	(0.20%)	(0.10%)
Nondeductible compensation	0.00%	0.90%	0.00%
Other	0.00%	0.20%	(0.20%)
Effective tax rate	21.80%	23.90%	21.10%