Income Taxes - Summary of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, Beginning balance	$ 856	$ 856	$ 775
Additions for tax positions related to prior years	398		81
Additions for tax positions related to current year	0	0	0
Reductions for tax positions of prior years	(52)
Unrecognized tax benefits, Ending balance	$ 1,202	$ 856	$ 856