Collaboration Agreements Schedule of Collaboration Revenue Earned From Bayer (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 1,608,022	$ 1,470,116	$ 3,119,507	$ 2,789,107
Bayer | Product and service, other
Disaggregation of Revenue [Line Items]
Revenues	262,863	210,355	510,791	404,294
Outside United States | Bayer | Product and service, other
Disaggregation of Revenue [Line Items]
Revenues	262,674	203,805	510,062	391,735
Outside United States | Bayer | Net profit in connection with commercialization
Disaggregation of Revenue [Line Items]
Revenues	246,302	190,883	478,370	365,759
Outside United States | Bayer | Reimbursement of Regeneron research and development expenses
Disaggregation of Revenue [Line Items]
Revenues	3,678	2,329	7,135	4,780
Outside United States | Bayer | Other
Disaggregation of Revenue [Line Items]
Revenues	$ 12,694	$ 10,593	$ 24,557	$ 21,196