Interim Financial Statements - Schedule of Statements of Operations Data (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 2,294.0	$ 1,743.7	$ 6,074.2	$ 4,694.1
Research and development	684.6	526.0	1,990.5	1,897.6
Selling, general, and administrative	326.9	304.4	1,042.5	890.1
Other operating (income) expense, net	(44.6)	(50.7)	(135.2)	(171.1)
Total operating expenses	1,240.9	1,005.2	3,664.6	3,160.0
Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of collaboration and contract manufacturing	143.0	109.6	454.5	289.6
Sanofi | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	353.3	175.0	869.3	232.8
Bayer | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	299.9	293.6	825.5	834.8
Other | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 158.6	36.8	$ 433.6	78.5
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		2,048.4		5,693.9
Research and development		663.4		2,353.5
Selling, general, and administrative		419.9		1,248.0
Other operating (income) expense, net		0.0		0.0
Total operating expenses		1,309.9		4,159.8
As Previously Reported | Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of collaboration and contract manufacturing		110.7		304.5
As Previously Reported | Sanofi | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		404.2		999.7
As Previously Reported | Bayer | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		302.8		868.0
As Previously Reported | Other | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		103.1		278.2
Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		(304.7)		(999.8)
Research and development		(137.4)		(455.9)
Selling, general, and administrative		(115.5)		(357.9)
Other operating (income) expense, net		(50.7)		(171.1)
Total operating expenses		(304.7)		(999.8)
Adjustments | Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of collaboration and contract manufacturing		(1.1)		(14.9)
Adjustments | Sanofi | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		(229.2)		(766.9)
Adjustments | Bayer | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		(9.2)		(33.2)
Adjustments | Other | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		$ (66.3)		$ (199.7)