Collaboration Agreements (Bayer HealthCare LLC) (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014
Collaboration Agreement [Line Items]
Other Collaboration Revenue	$ 157,596		$ 135,853		$ 415,679	$ 358,460
EYLEA
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement	130,510		85,351		326,567	213,291
Revenue Recognition, Milestone Method, Revenue Recognized	0		30,000		15,000	75,000
Reimbursement of Regeneron research and development expenses	1,827		4,394		6,948	26,235
Contracts Revenue	21,155		12,745		50,685	34,490
Other Collaboration Revenue	153,492		132,490		399,200	349,016
PDGFR-beta
Collaboration Agreement [Line Items]
Reimbursement of Regeneron research and development expenses	1,508		518		8,688	1,657
Contracts Revenue	2,596		2,845		7,791	7,787
Other Collaboration Revenue	$ 4,104		$ 3,363		$ 16,479	$ 9,444
BRVO
Collaboration Agreement [Line Items]
Reimbursement of Regeneron research and development expenses				$ 15,700
sales achievement - $200 million
Collaboration Agreement [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized		$ 15,000