Licensing and Commercialization Agreement (Details) $ in Thousands		1 Months Ended											3 Months Ended	12 Months Ended			22 Months Ended	102 Months Ended
	Jul. 22, 2019 shares	Sep. 30, 2019 USD ($)	Jul. 31, 2019 shares	May 31, 2019 USD ($) licensed_product shares	Jun. 30, 2018 USD ($)	Aug. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	May 31, 2014 USD ($)	Sep. 30, 2011 USD ($) shares	Sep. 30, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Feb. 27, 2020 USD ($)	Sep. 30, 2018 USD ($)
Agreement
Number of licensed products | licensed_product				1
Upfront fees received						$ 16,900
Total collaboration revenue														$ 0	$ 0	$ 209,977
License revenue
Agreement
Total collaboration revenue														0	0	152,912
Research and development activity revenue
Agreement
Total collaboration revenue														0	0	56,180
API transfer revenue
Agreement
Total collaboration revenue														0	0	754
Joint operating committee revenue
Agreement
Total collaboration revenue														0	$ 0	$ 131
RHO-adRP License Agreement | University of Florida Research Foundation (UFRF) | Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product
Agreement
Amount to be paid on achievement of milestone																			$ 23,500
RHO-adRP License Agreement | University of Florida Research Foundation (UFRF) | Specified Commercial Sales Milestones Related to a Licensed Product
Agreement
Amount to be paid on achievement of milestone																			$ 70,000
BEST1 License Agreement | University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn)
Agreement
Licensing agreement term				10 years
Licensing and Commercialization Agreement | Novartis Pharma AG
Agreement
Upfront fees received							$ 189,800				$ 200,000
Total collaboration revenue													$ 206,700
Licensing and Commercialization Agreement | Novartis Pharma AG | Achievement of specified patient enrollment milestones
Agreement
Patient enrollment-based milestone revenue achieved								$ 30,000	$ 50,000	$ 50,000							$ 130,000
Research and development | RHO-adRP License Agreement | University of Florida Research Foundation (UFRF)
Agreement
Payments for license fees					$ 500
Research and development | RHO-adRP License Agreement | University of Florida Research Foundation (UFRF) | Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product
Agreement
Payments for license fees					23,500
Research and development | RHO-adRP License Agreement | University of Florida Research Foundation (UFRF) | Specified Commercial Sales Milestones Related to a Licensed Product
Agreement
Payments for license fees					70,000
Research and development | BEST1 License Agreement | University Of Pennsylvania | Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product | Primary Licensed Product
Agreement
Payments for license fees				$ 200
Research and development | BEST1 License Agreement | University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn) | Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product | Primary Licensed Product
Agreement
Payments for license fees				15,700
Research and development | BEST1 License Agreement | University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn) | Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product | Other Licensed Product
Agreement
Payments for license fees				3,100
Research and development | BEST1 License Agreement | University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn) | Specified Commercial Sales Milestones Related to a Licensed Product | Primary Licensed Product
Agreement
Payments for license fees				48,000
Research and development | BEST1 License Agreement | University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn) | Specified Commercial Sales Milestones Related to a Licensed Product | Other Licensed Product
Agreement
Payments for license fees				9,600
General and administrative | RHO-adRP License Agreement | University of Florida Research Foundation (UFRF)
Agreement
Payments for license fees					$ 30
General and administrative | BEST1 License Agreement | University of Florida Research Foundation (UFRF) | Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product | Primary Licensed Product
Agreement
Payments for license fees				18
License Agreements | Archemix | C5 Licensed Product
Agreement
Licensing agreement term												12 years
License Agreements | Archemix | Achievement of specified clinical and regulatory milestones | C5 Licensed Product
Agreement
Payments for license fees												$ 1,000
Amount to be paid on achievement of milestone														$ 1,000
License Agreements | Archemix | First indication | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												30,500
License Agreements | Archemix | Second and third indication | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												23,500
License Agreements | Archemix | Sustained delivery applications | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												$ 2,500
License Agreements | University Of Massachusetts (UMass) | miniCEP290
Agreement
Shares issued for license fees (in shares) | shares	75,000		75,000
Licensing agreement term			10 years
License Agreements | Research and development | University Of Massachusetts (UMass) | miniCEP290
Agreement
Payments for license fees		$ 400
License Agreements | Research and development | University Of Massachusetts (UMass) | Achievement of specified clinical and regulatory milestones | miniCEP290
Agreement
Payments for license fees				$ 14,750
Shares issued for license fees (in shares) | shares				75,000
License Agreements | Research and development | University Of Massachusetts (UMass) | Specified Commercial Sales Milestones Related to a Licensed Product | miniCEP290
Agreement
Payments for license fees				$ 48,000
License Agreements | General and administrative | University Of Massachusetts (UMass) | miniCEP290
Agreement
Payments for license fees		$ 0
License Agreements | Series A Preferred Stock | Archemix | Achievement of specified clinical and regulatory milestones | C5 Licensed Product
Agreement
Shares issued for license fees (in shares) | shares												2,000,000
License Agreements | Series B Preferred Stock | Archemix | Achievement of specified clinical and regulatory milestones | C5 Licensed Product
Agreement
Shares issued for license fees (in shares) | shares												500,000
Subsequent Event | License Agreements | Archemix | Achievement of specified clinical and regulatory milestones | C5 Licensed Product
Agreement
Payments for license fees																		$ 2,000
Maximum | License Agreements | Archemix | Achievement of specified clinical and regulatory milestones | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												$ 56,500
Maximum | License Agreements | Archemix | First indication | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												30,500
Maximum | License Agreements | Archemix | Second and third indication | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												23,500
Maximum | License Agreements | Archemix | Sustained delivery applications | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												2,500
Maximum | License Agreements | Archemix | Achievement of specified commercial milestones | C5 Licensed Product
Agreement
Amount to be paid on achievement of milestone												$ 22,500