Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified		84 Months Ended		1 Months Ended				84 Months Ended			84 Months Ended		1 Months Ended
	Dec. 31, 2013 Acquisition agreement OSI Pharmaceuticals Anti-PDGF aptamers	Dec. 31, 2013 License agreement Archemix Anti-PDGF aptamers	Dec. 31, 2013 License agreement Archemix Fovista Achievement of specified clinical and regulatory milestones Maximum	Aug. 31, 2013 License agreement Archemix Fovista Initiation of planned Phase 3 clinical program of Fovista	Dec. 31, 2013 License agreement Archemix Fovista Achievement of specified commercial milestones Maximum	Dec. 31, 2013 License agreement Archemix Other anti-PDGF aptamer Achievement of specified clinical and regulatory milestones Maximum	Dec. 31, 2013 License agreement Archemix Other anti-PDGF aptamer Achievement of specified commercial milestones Maximum	Dec. 31, 2013 License agreement Archemix Anti-C5 aptamers	Dec. 31, 2013 License agreement Archemix Anti-C5 aptamers Achievement of specified commercial milestones Maximum	Dec. 31, 2013 License agreement Archemix Anti-C5 aptamers Achievement of specified development, clinical and regulatory milestones Maximum	Dec. 31, 2013 License, manufacturing and supply agreement Nektar	Dec. 31, 2013 License, manufacturing and supply agreement Nektar Achievement of specified clinical and regulatory milestones Maximum	Aug. 31, 2013 License, manufacturing and supply agreement Nektar Fovista Initiation of planned Phase 3 clinical program of Fovista	Dec. 31, 2013 License, manufacturing and supply agreement Nektar Fovista Achievement of specified commercial sale milestone
Commitments and contingencies
Amount of obligation to make one-time payments	$ 12.0
Amount to be paid on achievement of milestone			14.0		3.0	18.8	3.0		22.5	57.5		4.5		3.0
Royalty payable		0						0
Cumulative payments		$ 4.8		$ 2.5				$ 2.0			$ 1.8		$ 1.0