Collaboration Agreements - Schedule of Collaboration Revenue Earned From Bayer (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 1,663,496	$ 1,500,673	$ 4,783,003	$ 4,289,780
Bayer | Product and service, other
Disaggregation of Revenue [Line Items]
Revenues	264,373	236,625	775,164	640,919
Outside United States | Bayer | Product and service, other
Disaggregation of Revenue [Line Items]
Revenues	265,592	227,134	775,654	618,869
Outside United States | Bayer | Net profit in connection with commercialization
Disaggregation of Revenue [Line Items]
Revenues	243,152	205,367	721,522	571,126
Outside United States | Bayer | Reimbursement of Regeneron research and development expenses
Disaggregation of Revenue [Line Items]
Revenues	1,676	6,053	8,811	10,833
Outside United States | Bayer | Other
Disaggregation of Revenue [Line Items]
Revenues	$ 20,764	$ 15,714	$ 45,321	$ 36,910