Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2018 USD ($) Installment	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)
Other Commitments [Line Items]
Operating lease rent expense		$ 4.6	$ 2.2	$ 8.7	$ 4.2
Outstanding liability		1.4		1.4
Selling, General and Administrative
Other Commitments [Line Items]
Estimated fair value of grant expense	$ 1.7
Fair value of grant, discount rate	10.00%
Endowment Agreement
Other Commitments [Line Items]
Donation fund	$ 2.0
Annual installment payment of donation fund	$ 0.5
Number of annual installments | Installment	4
Other Accrued and Current Liabilities
Other Commitments [Line Items]
Deferred rent, current		0.9		0.9
Outstanding liability		1.0		1.0
Other Noncurrent Liabilities
Other Commitments [Line Items]
Deferred rent, noncurrent		6.0		6.0
Outstanding liability		$ 0.4		$ 0.4
Minimum [Member]
Other Commitments [Line Items]
Operating lease term		1 year		1 year
Maximum
Other Commitments [Line Items]
Operating lease term		11 years		11 years