Income Taxes - Schedule of Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits, beginning of the year	$ 8,564	$ 8,132	$ 7,737
Additions for tax positions of prior years	5	24	263
Additions for tax positions related to the current year	1,839	1,625	1,247
Reductions due to lapse of applicable statute of limitations	(1,399)	(1,217)	(1,115)
Subtotal	9,009	8,564	8,132
Interest and penalties	1,862	1,909	2,008
Total gross unrecognized tax benefits, end of the year	$ 10,871	$ 10,473	$ 10,140