Financial Instruments and Fair Value , Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 564.4	$ 548.1
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	181.9	288.9
U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	207.0	193.6
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	165.1	26.4
Certificates of deposit and term deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5.4	34.2
Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5.0	5.0
Recurring Basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,422.6	1,348.1
Recurring Basis [Member] | Fair Value [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	825.3	878.7
Recurring Basis [Member] | Fair Value [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	597.3	469.4
Recurring Basis [Member] | Fair Value [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	181.9	288.9
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	181.9	288.9
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	396.1	268.6
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	351.8	259.3
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	44.3	9.3
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	320.8	115.8
Recurring Basis [Member] | Fair Value [Member] | Commercial paper | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Commercial paper | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	320.8	115.8
Recurring Basis [Member] | Fair Value [Member] | Commercial paper | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	45.3	50.4
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	45.3	50.4
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	447.4	593.9
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	447.4	593.9
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5.0	5.0
Recurring Basis [Member] | Fair Value [Member] | Municipal bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Municipal bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5.0	5.0
Recurring Basis [Member] | Fair Value [Member] | Municipal bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Marketable equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	26.1	25.5
Recurring Basis [Member] | Fair Value [Member] | Marketable equity securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	26.1	25.5
Recurring Basis [Member] | Fair Value [Member] | Marketable equity securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Fair Value [Member] | Marketable equity securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0.0	0.0
Recurring Basis [Member] | Reported as [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,422.6	1,348.1
Recurring Basis [Member] | Reported as [Member] | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	832.1	774.5
Recurring Basis [Member] | Reported as [Member] | Marketable equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	26.1	25.5
Recurring Basis [Member] | Reported as [Member] | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	548.8	502.6
Recurring Basis [Member] | Reported as [Member] | Long-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 15.6	$ 45.5