Subsequent Events - Textual (Details) - Novartis [Member] - Subsequent Event [Member]	May 07, 2019 USD ($)
Subsequent Event [Line Items]
Term of collaborative research and development agreement	20 months
Maximum milestone receivable	$ 14,000,000
Payment terms	22 months
Annual payments receivable	$ 8,000,000
Milestone One [Member]
Subsequent Event [Line Items]
Maximum milestone receivable	5,000,000
Milestone Two [Member]
Subsequent Event [Line Items]
Maximum milestone receivable	4,000,000
Milestone Three [Member]
Subsequent Event [Line Items]
Maximum milestone receivable	$ 5,000,000