Statement of Cash Flows - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Accrued capital expenditures	$ 133,700,000	$ 54,500,000	$ 41,800,000
Treasury stock, shares acquired (in shares)	722,596
Cost of treasury stock shares received	$ 254,000,000.0
Capital lease obligations incurred	$ 0	$ 0	$ 201,200,000
Sanofi Collaboration Agreement, Immuno-oncology
Condensed Cash Flow Statements, Captions [Line Items]
Treasury stock, shares acquired (in shares)	210,733	215,387
Cost of treasury stock shares received	$ 73,300,000	$ 75,800,000