Income Taxes - (Benefit) Provision for Income Taxes Differs from Amounts Computed by Applying Statutory Federal Corporate Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Tax Disclosure [Abstract]
(Benefit) provision for income taxes at statutory rate	$ (10,712)	$ 242	$ (13,643)	$ 523
Tax effect of:
Tax-exempt investment income	(10)	(5)	(20)	(10)
Change in the beginning of the period balance of the valuation allowance for deferred tax assets allocated to federal income taxes	57	2	57	2
Stock-based compensation	13	22	17	22
State income taxes, net of federal income tax benefit and state valuation allowance	(65)	122	(6)	158
Other	9	(8)	18	(2)
Income tax expense (benefit)	$ (10,708)	$ 375	$ (13,577)	$ 693