Collaboration Agreements (Sanofi) (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 ZALTRAP Agreement	Sep. 30, 2013 ZALTRAP Agreement	Sep. 30, 2014 ZALTRAP Agreement	Sep. 30, 2013 ZALTRAP Agreement	Jun. 30, 2013 Ang2	Sep. 30, 2013 Ang2	Jul. 31, 2014 Antibody Collaboration	Sep. 30, 2014 Antibody Collaboration	Sep. 30, 2013 Antibody Collaboration	Sep. 30, 2014 Antibody Collaboration	Sep. 30, 2013 Antibody Collaboration family	Mar. 31, 2014 PDGF	Jun. 30, 2013 PDGF	Sep. 30, 2014 PDGF	Sep. 30, 2013 PDGF	Sep. 30, 2014 Sanofi [Member]
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement					$ (1,008,000)	$ (6,575,000)	$ (4,912,000)	$ (22,581,000)				$ (12,830,000)	$ 0	$ (17,125,000)	$ 0
Number of Payments the Company made															2	2
Research and Development Asset Acquired Other than Through Business Combination, Written-off									10,000,000	10,000,000				0	20,000,000		10,000,000		10,000,000	33,750,000
Number of families of novel antibodies															2
Percentage of Trial Costs borne by collaborating party														80.00%
Percentage of Trial Costs borne by entity														20.00%
Research and development	337,728,000	224,045,000	919,608,000	591,807,000								28,400,000		81,300,000
Other Research and Development Expense																5,000,000
Milestone payment																		30,000,000
Reimbursement of Regeneron research and development expenses					1,261,000	1,316,000	3,691,000	5,497,000				140,497,000	133,128,000	405,212,000	338,027,000
Contracts Revenue					756,000	2,625,000	4,417,000	6,610,000				4,249,000	3,865,000	14,745,000	11,608,000
Revenue from Related Parties	132,925,000	134,359,000	406,028,000	319,161,000	1,009,000	(2,634,000)	3,196,000	(10,474,000)				131,916,000	136,993,000	402,832,000	329,635,000
Payments for Purchase of Other Assets											$ 67,500,000