Inventory - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Inventory [Line Items]
Prepayment made for manufacturing services	$ 14,155	$ 8,578	[1]
Contract manufacturing organization (CMO)
Inventory [Line Items]
Prepayment made for manufacturing services	$ 10,100	$ 7,200

[1] The consolidated balance sheet as of December 31, 2019 has been derived from the audited consolidated balance sheet included in the Company’s 2019 Annual Report on Form 10-K filed with the Securities and Exchange Commission on February 27, 2020.