Income Taxes - Summary of Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits, Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 5,655	$ 4,741	$ 5,724
Additions for tax positions of prior years	304	1,404	179
Reductions for tax positions of prior years	(1,350)	(490)	(1,162)
Balance at end of year	$ 4,609	$ 5,655	$ 4,741