Revenue - Product Revenue Allowance and Reserves (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Disclosure Of Product Revenue Reserves And Allowances [Line Items]
Beginning balance at January 1, 2020	$ 2,241	$ 0
Provision related to sales in the current year	1,547	1,140
Adjustments related to prior period sales	(337)
Deductions applied and payments made	(1,909)	(89)
Ending balance at June 30, 2020	1,542	1,051
Chargebacks, Discounts and Fees [Member]
Disclosure Of Product Revenue Reserves And Allowances [Line Items]
Beginning balance at January 1, 2020	1,618	0
Provision related to sales in the current year	864	877
Adjustments related to prior period sales	(387)
Deductions applied and payments made	(1,185)	(89)
Ending balance at June 30, 2020	910	788
Government and Other Rebates [Member]
Disclosure Of Product Revenue Reserves And Allowances [Line Items]
Beginning balance at January 1, 2020	271	0
Provision related to sales in the current year	247	76
Deductions applied and payments made	(400)
Ending balance at June 30, 2020	118	76
Returns [Member]
Disclosure Of Product Revenue Reserves And Allowances [Line Items]
Beginning balance at January 1, 2020	352	0
Provision related to sales in the current year	436	187
Adjustments related to prior period sales	50
Deductions applied and payments made	(324)
Ending balance at June 30, 2020	$ 514	$ 187