Income Taxes - Reconciliation of Effective Tax Rate and Statutory Federal Income Tax Rate (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	35.00%	35.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	6.90%	6.50%	6.70%	6.70%
Tax-exempt interest on municipal obligations	(1.70%)	(0.80%)	(1.90%)	(0.60%)
Increase in cash value of insurance policies	(1.20%)	(1.30%)	(1.60%)	(1.40%)
Low income housing tax credits	(0.30%)		(0.30%)
Other		0.40%	0.10%	0.20%
Effective Tax Rate	38.70%	39.80%	38.00%	39.90%