Financial Instruments and Risk Management Financial Instruments and Risk Management (Rollforward of Contingent Consideration) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 223.2	$ 250.7
Business Combination Contingent Consideration Liability Payments	(52.3)
Business Combination, Contingent Consideration Arrangements, Reclassifications	0.0
Accretion expense	6.1
Fair value loss	18.7
Prepaid expenses and other current assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	119.8	120.4
Business Combination Contingent Consideration Liability Payments	(52.3)
Business Combination, Contingent Consideration Arrangements, Reclassifications	34.8
Accretion expense	0.0
Fair value loss	16.9
Other long-term obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	103.4	$ 130.3
Business Combination Contingent Consideration Liability Payments	0.0
Business Combination, Contingent Consideration Arrangements, Reclassifications	(34.8)
Accretion expense	6.1
Fair value loss	$ 1.8