Fair Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Assets:
Short-term investments	$ 0.0	$ 3.6
Liabilities:
Contingent purchase price obligations	71.9	107.7
Carrying Amount
Assets:
Cash and cash equivalents	5,600.5	4,305.7
Short-term investments	0.0	3.6
Marketable equity securities	1.6	1.6
Non-marketable equity securities	8.9	9.0
Foreign currency derivatives	0.6	0.6
Liabilities:
Short-term debt	3.9	10.1
Foreign currency derivatives	0.3	0.4
Contingent purchase price obligations	71.9	107.7
Long-term debt, including current portion	5,807.3	5,134.3
Fair Value
Assets:
Cash and cash equivalents	5,600.5	4,305.7
Short-term investments	0.0	3.6
Marketable equity securities	1.6	1.6
Non-marketable equity securities	8.9	9.0
Foreign currency derivatives	0.6	0.6
Liabilities:
Short-term debt	3.9	10.1
Foreign currency derivatives	0.3	0.4
Contingent purchase price obligations	71.9	107.7
Long-term debt, including current portion	6,380.6	5,316.4
Contingent purchase price obligations
Changes in Contingent Purchase Price Obligations [Roll Forward]
January 1	107.7	146.5
Acquisitions	14.4	51.1
Revaluation and interest	(21.9)	(18.0)
Payments	(31.3)	(71.4)
Foreign currency translation	3.0	(0.5)
December 31	71.9	107.7
Fair Value, Recurring [Member]
Assets:
Cash and cash equivalents	5,600.5	4,305.7
Short-term investments		3.6
Marketable equity securities	1.6	1.6
Foreign currency derivatives	0.6	0.6
Liabilities:
Foreign currency derivatives	0.3	0.4
Contingent purchase price obligations	71.9	107.7
Fair Value, Recurring [Member] | Level 1
Assets:
Cash and cash equivalents	5,600.5	4,305.7
Short-term investments		3.6
Marketable equity securities	1.6	1.6
Fair Value, Recurring [Member] | Level 2
Assets:
Foreign currency derivatives	0.6	0.6
Liabilities:
Foreign currency derivatives	0.3	0.4
Fair Value, Recurring [Member] | Level 3
Liabilities:
Contingent purchase price obligations	$ 71.9	$ 107.7