Commitments and Contingencies (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2014
Acquisition agreement | OSI Pharmaceuticals | PDGF Licensed Products
Commitments and contingencies
Amount to be paid on achievement of milestone		$ 12.0
License Agreements | Licensor | PDGF Licensed Products
Commitments and contingencies
Royalty payable		0.0
License Agreements | Licensor | Fovista | Achievement of specified clinical and regulatory milestones | Maximum
Commitments and contingencies
Amount to be paid on achievement of milestone		14.0
License Agreements | Licensor | Fovista | Achievement of specified commercial milestones | Maximum
Commitments and contingencies
Amount to be paid on achievement of milestone		3.0
License Agreements | Licensor | Other anti-PDGF aptamer | Achievement of specified clinical and regulatory milestones | Maximum
Commitments and contingencies
Amount to be paid on achievement of milestone		18.8
License Agreements | Licensor | Other anti-PDGF aptamer | Achievement of specified commercial milestones | Maximum
Commitments and contingencies
Amount to be paid on achievement of milestone		3.0
License Agreements | Licensor | C5 Licensed Product
Commitments and contingencies
Royalty payable		0.0
License Agreements | Licensor | C5 Licensed Product | Achievement of specified commercial milestones | Maximum
Commitments and contingencies
Amount to be paid on achievement of milestone		22.5
License Agreements | Licensor | C5 Licensed Product | Achievement of specified development, clinical and regulatory milestones | Maximum
Commitments and contingencies
Amount to be paid on achievement of milestone		57.5
Supply Agreement | Supplier
Commitments and contingencies
Payment upon entry into Novartis Agreement	$ 19.8
Supply Agreement | Supplier | Achievement of specified clinical and regulatory milestones | Maximum
Commitments and contingencies
Amount to be paid on achievement of milestone		6.5
Supply Agreement | Supplier | Fovista | Achievement of specified commercial sale milestone
Commitments and contingencies
Amount to be paid on achievement of milestone		$ 3.0
Supply Agreement | Agilent Technologies
Commitments and contingencies
Initial term of agreement		5 years
Period after notice for termination of agreement		12 months