Product Revenue Reserves and Allowances - Product Revenue Allowance and Reserves (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Disclosure of Product Revenue Reserves and Allowances [Line Items]
Beginning balance at January 1, 2019	$ 0
Provision related to sales in the current year	1,361
Deductions applied and payments made	(454)
Ending balance at September 30, 2019	907
Chargebacks, Discounts and Fees [Member]
Disclosure of Product Revenue Reserves and Allowances [Line Items]
Beginning balance at January 1, 2019	0
Provision related to sales in the current year	833
Deductions applied and payments made	(178)
Ending balance at September 30, 2019	655
Government and Other Rebates [Member]
Disclosure of Product Revenue Reserves and Allowances [Line Items]
Beginning balance at January 1, 2019	0
Provision related to sales in the current year	161
Deductions applied and payments made	(105)
Ending balance at September 30, 2019	56
Returns [Member]
Disclosure of Product Revenue Reserves and Allowances [Line Items]
Beginning balance at January 1, 2019	0
Provision related to sales in the current year	367
Deductions applied and payments made	(171)
Ending balance at September 30, 2019	$ 196