Business Overview and Summary of Significant Accounting Policies - Schedule of Statements of Operations Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 1,927.8	$ 1,663.5	$ 1,608.0	$ 1,511.5	$ 1,582.4	$ 1,500.7	$ 1,470.1	$ 1,319.0	$ 6,710.8	$ 5,872.2	$ 4,860.4
Income from operations									2,534.4	2,079.6	1,330.7
Income before income taxes									2,553.5	2,078.5	1,329.8
Income tax expense									(109.1)	(880.0)	(434.3)
Net income	$ 820.4	$ 594.7	$ 551.4	$ 478.0	$ 173.5	$ 388.3	$ 387.7	$ 248.9	2,444.4	1,198.5	895.5
Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of collaboration and contract manufacturing									254.1	194.6	105.1
Balance Without Adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									6,515.3
Income from operations									2,356.4
Income before income taxes									2,375.5
Income tax expense									(71.9)
Net income									2,303.6
Balance Without Adoption of ASC 606 | Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of collaboration and contract manufacturing									236.6
Accounting Standards Update 2014-09 | Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									(195.5)
Income from operations									(178.0)
Income before income taxes									(178.0)
Income tax expense									37.2
Net income									(140.8)
Accounting Standards Update 2014-09 | Adjustments | Collaboration and contract manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of collaboration and contract manufacturing									(17.5)
Sanofi | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									1,111.1	877.2	658.7
Sanofi | Balance Without Adoption of ASC 606 | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									947.3
Sanofi | Accounting Standards Update 2014-09 | Adjustments | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									(163.8)
Other | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									416.8	$ 338.4	$ 119.0
Other | Balance Without Adoption of ASC 606 | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									385.1
Other | Accounting Standards Update 2014-09 | Adjustments | Product and service, other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									$ (31.7)