Income Taxes - Provision (Benefit) for Income Taxes Differs from Amounts Computed by Applying Statutory Federal Corporate Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes at statutory rate	$ 552	$ (2,931)
Tax effect of:
Tax-exempt investment income	(14)	(10)
Stock option expirations	229	4
State income taxes, net of federal income tax benefit and state valuation allowance	69	59
Other	10	9
Income tax expense (benefit)	$ 846	$ (2,869)