Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Income Tax Examination [Line Items]
Unrecognized tax benefits	$ 0		$ 0
Income tax examination			Federal and state tax returns for the 2012 through 2015 tax years are subject to examination
Amortization of low-income housing credit investments reflected as income tax expense	390,000	$ 477,000	$ 780,000	$ 971,000
Tax benefits recorded as income tax expense			189,000
Carrying value of investment in affordable housing credits	11,200,000		$ 11,200,000		$ 12,000,000
Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Income tax examination period			2012
Latest Tax Year [Member]
Income Tax Examination [Line Items]
Income tax examination period			2015
Tax Credit [Member]
Income Tax Examination [Line Items]
Affordable housing tax credits	$ 713,000		$ 713,000