Collaboration Agreements (Bayer) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Collaboration Agreement [Line Items]
Other Collaboration Revenue	$ 236,625	$ 191,298	$ 640,919	$ 562,786
EYLEA
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement	205,367	170,854	571,126	484,181
Reimbursement of Regeneron research and development expenses	6,053	2,219	10,833	7,186
Contracts Revenue	15,714	6,077	36,910	45,924
Other Collaboration Revenue	227,134	179,150	618,869	537,291
Ang2 antibody and PDGFR-beta antibody
Collaboration Agreement [Line Items]
Reimbursement of Regeneron research and development expenses	7,325	7,433	15,614	14,165
Contracts Revenue	2,166	4,715	6,436	11,330
Other Collaboration Revenue	$ 9,491	$ 12,148	$ 22,050	$ 25,495