Commitments and Contingencies - Narrative (Details) € in Thousands	1 Months Ended		12 Months Ended		51 Months Ended	99 Months Ended
	Oct. 31, 2010 EUR (€)	Oct. 31, 2010 USD ($)	Dec. 31, 2018 USD ($) arrangement renewal_term	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) arrangement	Dec. 31, 2018 USD ($) arrangement
Commitments and Contingencies [Line Items]
License fee expense			$ 700,000
Number of renewal terms | renewal_term			2
Renewal term			3 years		3 years	3 years
Rent expense			$ 300,000	$ 300,000
Operating expenses of leases			$ 300,000	300,000
Yale University
Commitments and Contingencies [Line Items]
Term of agreement			5 years
Proceeds from collaboration					$ 900,000
University of Texas
Commitments and Contingencies [Line Items]
Number of arrangements | arrangement			2		2	2
Nonrefundable upfront license documentation fee			$ 10,000
Annual license maintenance fee			10,000
Potential milestone payment for initiation of defined clinical trials			600,000		$ 600,000	$ 600,000
University of Texas | United States
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			2,000,000		2,000,000	2,000,000
University of Texas | Other Regions
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			500,000		500,000	500,000
RICC
Commitments and Contingencies [Line Items]
Potential future milestone payments per licensed product			5,200,000.0		5,200,000.0	5,200,000.0
Payments for raw materials			300,000	$ 600,000
t2cure
Commitments and Contingencies [Line Items]
Nonrefundable upfront license documentation fee		$ 46,000
Annual license maintenance fee	€ 3					3,000
Potential milestone payment for initiation of defined clinical trials			$ 700,000		700,000	700,000
Term of agreement			10 years
Period to terminate agreement			60 days
t2cure | United States
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			$ 2,500,000		2,500,000	2,500,000
t2cure | European Union or Japan
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval			1,500,000.0		$ 1,500,000.0	$ 1,500,000.0
BWH
Commitments and Contingencies [Line Items]
Potential milestone payments			2,600,000
One-time sales milestone payment			$ 300,000