Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Benefit [Line Items]
Tax provisions (benefits)	$ 131,000	$ (2,945,000)
Effective tax rate	3.20%	52.30%
Deferred tax asset valuation allowance	$ 21,700,000		$ 21,700,000
Interest and penalties related to unrecognized tax benefits	0	$ 0
Uncertain tax portions	0
Cumulative adjustment to retained earnings		1,400,000
Stock Option Exercises [Member]
Income Tax Benefit [Line Items]
Tax provisions (benefits)	$ 111,000	$ 241,000