Interim Financial Statements - Schedule of Statements of Operations Data (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 1,952.0	$ 1,577.8	$ 3,780.2	$ 2,950.4
Research and development	722.0	885.5	1,305.9	1,371.6
Selling, general, and administrative	348.3	294.6	715.6	585.7
Other operating (income) expense, net	(50.2)	(63.7)	(90.6)	(120.4)
Total operating expenses	1,295.6	1,262.2	2,423.7	2,154.8
Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of goods sold	173.0	78.8	311.5	180.0
Sanofi | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	269.1	75.8	516.0	57.8
Bayer | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	244.2	277.2	525.6	541.2
Other | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 211.8	19.5	$ 275.0	41.7
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		1,933.7		3,645.5
Research and development		1,048.3		1,690.1
Selling, general, and administrative		417.3		828.1
Other operating (income) expense, net		0.0		0.0
Total operating expenses		1,618.1		2,849.9
As Previously Reported | Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of goods sold		85.5		193.8
As Previously Reported | Sanofi | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		349.1		595.5
As Previously Reported | Bayer | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		289.0		565.2
As Previously Reported | Other | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		90.3		175.1
Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		(355.9)		(695.1)
Research and development		(162.8)		(318.5)
Selling, general, and administrative		(122.7)		(242.4)
Other operating (income) expense, net		(63.7)		(120.4)
Total operating expenses		(355.9)		(695.1)
Adjustments | Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of goods sold		(6.7)		(13.8)
Adjustments | Sanofi | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		(273.3)		(537.7)
Adjustments | Bayer | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		(11.8)		(24.0)
Adjustments | Other | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		$ (70.8)		$ (133.4)