Summary of Sales by End Market (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Net revenue	$ 6,539	$ 8,646	$ 14,260	$ 27,617
End-customer
Disaggregation Of Revenue [Line Items]
Net revenue	5,087	3,727	9,845	11,068
Distributors
Disaggregation Of Revenue [Line Items]
Net revenue	$ 1,452	$ 4,919	$ 4,415	$ 16,549