Revenue Recognition - Schedule of Net Product Revenues Disaggregated by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenues									$ 116,640	$ 40,130	$ 22,546
Product revenue, net
Disaggregation of Revenue [Line Items]
Total revenues	$ 28,375	$ 35,743	$ 27,164	$ 20,362	$ 14,070	$ 7,176	$ 2,265	$ 606	111,644	24,117	0
Product revenue, net | United States
Disaggregation of Revenue [Line Items]
Total revenues									104,708	24,117	0
Product revenue, net | Europe
Disaggregation of Revenue [Line Items]
Total revenues									$ 6,936	$ 0	$ 0