Statement of Cash Flows - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Accrued capital expenditures	$ 54.5	$ 41.8	$ 28.2
Cost of Treasury stock shares received	$ 80.2		0.0
Capital lease obligations incurred		$ 201.2	$ 154.9
Sanofi Collaboration Agreement, Immuno-oncology
Condensed Cash Flow Statements, Captions [Line Items]
Treasury stock, shares acquired (in shares)	215,387
Cost of Treasury stock shares received	$ 75.8