Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	35.00%	35.00%
State tax, net of federal tax benefit	3.10%	2.70%	3.10%
Adjustment to net deferred tax asset for enacted changes in tax laws and rates	(0.50%)	13.40%	0.00%
Nondeductible acquisition costs	0.40%	0.00%	0.20%
Tax-exempt interest	(0.80%)	(1.90%)	(2.10%)
Bank-owned life insurance income	(0.00%)	(0.50%)	(0.30%)
Excess tax benefits from share-based compensation	(1.80%)	(2.00%)	(1.40%)
Surrender of bank-owned life insurance policies	0.00%	7.30%	0.00%
Federal tax credits, net of amortization	(0.10%)	(0.30%)	(0.50%)
Other	(0.20%)	0.00%	0.00%
Effective tax rate	21.10%	53.70%	34.00%