Income Taxes - Significant Components of our Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current Federal, State and Local, Tax Expense (Benefit) [Abstract]
Total provision for income taxes	$ 253	$ 269	$ 249
Changes in federal and state tax rates	586	(4,058)	0
Geographic Distribution, Domestic [Member]
Current Federal, State and Local, Tax Expense (Benefit) [Abstract]
Total provision for income taxes	0	0	0
Geographic Distribution, Foreign [Member]
Current Federal, State and Local, Tax Expense (Benefit) [Abstract]
Total provision for income taxes	$ 253	$ 269	$ 249