Collaboration Agreements (EYLEA) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Collaboration Agreement [Line Items]
Number of sales milestone payments the Company received	1	2
Levels of twelve month sales at which sales milestone payments were received - 500 million		$ 500,000,000
Levels of twelve month sales at which sales milestone payments were received - 600 million		600,000,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis	12 months	12 months
sales achievement - $500 million
Collaboration Agreement [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized		15,000,000
sales achievement - $600 million
Collaboration Agreement [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized		15,000,000
sales achievement - $200 million
Collaboration Agreement [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized	15,000,000
Collaboration Agreement with Bayer HealthCare LLC [Member]
Collaboration Agreement [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized	15,000,000	30,000,000
Starting specified levels of annual sales at which sales milestone payments maybe received -$200 million	200,000,000
Reimbursement of Regeneron research and development expenses	2,657,000	20,347,000
BRVO
Collaboration Agreement [Line Items]
Reimbursement of Regeneron research and development expenses		$ 15,700,000