Net Product Revenue - Summary of Balances and Activity in Each of Product Revenue Allowance and Reserve Categories (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2019	$ 1,820	$ 348
Provision related to current period sales	5,932	1,350
Adjustment related to prior period sales	17	(29)
Credits or payments made during the period	(2,883)	(521)
Balance at June 30, 2020	4,886	1,148
Chargebacks, Discounts and Fees [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2019	270	50
Provision related to current period sales	1,044	438
Adjustment related to prior period sales	(66)	(4)
Credits or payments made during the period	(1,093)	(311)
Balance at June 30, 2020	155	173
Government and Other Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2019	1,353	293
Provision related to current period sales	4,830	774
Adjustment related to prior period sales	83	(25)
Credits or payments made during the period	(1,790)	(210)
Balance at June 30, 2020	4,476	832
Returns [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2019	197	5
Provision related to current period sales	58	138
Adjustment related to prior period sales	0	0
Credits or payments made during the period	0	0
Balance at June 30, 2020	$ 255	$ 143