Income Taxes - Reconciliation of the Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 2,650	$ 29	$ 265
Additions attributable to state and local apportionment	2,068	2,650
Reductions for tax positions of prior years		(29)	(236)
Balance at end of year	$ 4,718	$ 2,650	$ 29