Income Taxes - Reconciliation of Effective Tax Rate and Statutory Federal Income Tax Rate (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 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	7.00%	6.70%	6.60%	6.80%
Tax-exempt interest on municipal obligations	(2.30%)	(0.60%)	(2.00%)	(0.50%)
Increase in cash value of insurance policies	(2.20%)	(1.30%)	(1.80%)	(1.40%)
Low income housing tax credits	(1.40%)		(0.70%)
Other	0.80%	(0.30%)	0.40%	0.10%
Effective Tax Rate	36.90%	39.50%	37.50%	40.00%