Subsequent Event - Narrative (Details) - miniCEP290 License Agreement - University Of Massachusetts (UMass) - Subsequent Event $ / shares in Units, $ in Thousands	Jul. 22, 2019 USD ($) $ / shares shares
Subsequent Event [Line Items]
Payments for license fees	$ 400
Shares issued (in shares) | shares	75,000
Shares issued price (usd per share) | $ / shares	$ 0.001
Achievement of specified clinical and regulatory milestones
Subsequent Event [Line Items]
Amount to be paid on achievement of milestone	$ 14,750
Shares to be issued upon achievement of milestone | shares	75,000
Achievement of specified commercial milestones
Subsequent Event [Line Items]
Amount to be paid on achievement of milestone	$ 48,000