Company's Deferred Tax Assets, Net of Deferred Tax Liabilities and Valuation Allowance (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Deferred tax assets, net of deferred tax liabilities	$ 16,783	$ 10,308
Valuation allowance	(1,159)	(1,015)
Deferred tax assets, net of deferred tax liabilities and valuation allowance	$ 15,624	$ 9,293