Income Taxes - Benefit from Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
United States—Federal	$ 45		$ 4
United States—State	700	$ 164	92
Total current	745	164	96
Deferred:
United States—Federal	1,972	1,777	(1,968)
United States—State	1,956	(914)	(1,325)
Ireland and United Kingdom	(26,793)	1,278	(5,435)
Change in valuation allowance	22,865	(2,141)	8,728
Provision for income taxes	$ 745	$ 164	$ 96