Net Product Revenue - Summary of Balance of Receivables and Contract Liabilities Related to Net Product Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Accounts receivable	$ 10,673	$ 10,496
Contract liabilities included in "Accrued liabilities"	832	2,165
Accounts Receivable [Member]
Disaggregation Of Revenue [Line Items]
Accounts receivable	10,330	6,946
Accrued Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Contract liabilities included in "Accrued liabilities"	$ 2,645	$ 1,550