Commitments and Contingencies - Narrative (Details)		3 Months Ended
	May 02, 2018 USD ($) ft²	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Oct. 31, 2018 ft²
Loss Contingencies [Line Items]
Discount rate (as a percentage)		9.00%
Operating lease costs		$ 2,600,000	$ 2,300,000
Weighted average remaining lease term		9 years 1 month 6 days
Weighted-average discount rate (as a percentage)		9.00%
Cash paid for lease liabilities		$ 2,200,000	700,000
Sublease income		900,000	0
DMSA
Loss Contingencies [Line Items]
Purchase order executed		14,600,000		$ 21,200,000
Non-refundable purchase commitments		7,600,000		$ 11,200,000
Costs incurred		1,000,000.0	3,600,000
Payments for development and manufacturing services		$ 3,200,000	$ 2,600,000
Headquarters Lease
Loss Contingencies [Line Items]
Area under lease | ft²	148,020
Lease period	10 years
Lease renewal option term	10 years
Headquarters Lease | Landlord Funded Tenant Improvements
Loss Contingencies [Line Items]
Tenant improvement allowance repayable in rent	$ 4,400,000
New Premises Sublease Agreement
Loss Contingencies [Line Items]
Rentable square feet | ft²					36,835
Sublease term					5 years
Minimum | Headquarters Lease
Loss Contingencies [Line Items]
Lease renewal notice period	9 months
Maximum
Loss Contingencies [Line Items]
Leasehold improvements	$ 25,900,000
Maximum | Headquarters Lease
Loss Contingencies [Line Items]
Lease renewal notice period	12 months