Commitments and Contingencies - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended	5 Months Ended	12 Months Ended
	Nov. 30, 2016 USD ($) ft² consecutive_extension_period	Jun. 30, 2018 USD ($)	May 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Lease space occupied (in square feet) | ft²	51,000
Number of consecutive extension periods | consecutive_extension_period	1
Renewal term	5 years
Renewal notice period	12 months
Tenant improvement allowance	$ 0.5		$ 2.8
Security deposit, in form of letter of credit	$ 1.3
Sublease term			3 years
Early termination fee		$ 0.7
Rent expense				$ 4.0	$ 3.5
Costs incurred, third party agreements				$ 0.5
Minimum
Loss Contingencies [Line Items]
Cancellation notice period, technology agreements				30 days
Potential costs, third party agreements				$ 12.5
Maximum
Loss Contingencies [Line Items]
Cancellation notice period, technology agreements				90 days
Potential costs, third party agreements				$ 12.9
License And Collaboration Agreements | Maximum
Loss Contingencies [Line Items]
Potential costs, technology agreements				13.4
Costs incurred, technology agreements				$ 0.2