Revenue Recognition - Disaggregated Revenues by Timing of Transfer of Goods or Services (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Disaggregated Revenue	$ 28,424	$ 4,011	$ 50,593	$ 10,655
Product Revenue, Net
Disaggregation of Revenue [Line Items]
Disaggregated Revenue	27,164	2,265	47,526	2,871
Collaboration and License Revenue
Disaggregation of Revenue [Line Items]
Disaggregated Revenue	1,260	1,746	3,067	7,784
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Disaggregated Revenue	27,164	2,265	47,526	2,871
Transferred at a point in time | Product Revenue, Net
Disaggregation of Revenue [Line Items]
Disaggregated Revenue	27,164	2,265	47,526	2,871
Transferred over time
Disaggregation of Revenue [Line Items]
Disaggregated Revenue	1,260	1,746	3,067	7,784
Transferred over time | Collaboration and License Revenue
Disaggregation of Revenue [Line Items]
Disaggregated Revenue	$ 1,260	$ 1,746	$ 3,067	$ 7,784