Financial Instruments − Schedule of Company's Financial Instruments Measured at Fair value on Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Investment securities, current:
Debt securities, current	$ 4,775.4	$ 4,332.9
Investment securities, non-current:
Total	92.8	94.2
Executive deferred compensation plan trust	16.7	18.4
Prepaid expenses and other current assets
Investment securities, non-current:
Executive deferred compensation plan trust	1.5	2.2
Other assets
Investment securities, non-current:
Executive deferred compensation plan trust	15.2	16.3
Accrued Expenses And Other Current Liabilities
Liabilities:
Contingent consideration	18.6	51.0
Other Noncurrent Liabilities
Liabilities:
Contingent consideration		17.9
Corporate and sovereign debt securities
Investment securities, current:
Debt securities, current	1,596.3	1,349.6
Municipal bonds
Investment securities, current:
Debt securities, current	68.2	66.6
Asset-backed securities
Investment securities, current:
Debt securities, current	1,017.1	868.2
Mortgage-backed securities
Investment securities, current:
Debt securities, current	1,692.4	1,651.0
Mutual fund
Investment securities, non-current:
Fixed-income mutual fund and Pooled investment fund measured at NAV	27.7	27.6
Pooled investment fund measured at NAV
Investment securities, non-current:
Fixed-income mutual fund and Pooled investment fund measured at NAV	12.9	12.9
Level 1
Investment securities, non-current:
Executive deferred compensation plan trust	16.7	18.4
Level 1 \| Mutual fund
Investment securities, non-current:
Fixed-income mutual fund and Pooled investment fund measured at NAV	27.7	27.6
Level 1 \| Money market mutual funds
Financial Assets:
Cash and cash equivalents	28.2	64.3
Level 2
Investment securities, non-current:
Available-for-sale debt securities	52.2	53.7
Liabilities:
Contingent consideration	18.6	68.9
Level 2 \| U.S. treasury notes
Investment securities, current:
Debt securities, current	401.4	397.5
Level 2 \| Corporate and sovereign debt securities
Investment securities, current:
Debt securities, current	1,596.3	1,349.6
Level 2 \| Municipal bonds
Investment securities, current:
Debt securities, current	68.2	66.6
Level 2 \| Asset-backed securities
Investment securities, current:
Debt securities, current	1,017.1	868.2
Level 2 \| Mortgage-backed securities
Investment securities, current:
Debt securities, current	1,692.4	1,651.0
Level 2 \| U.S. Treasury bills
Financial Assets:
Cash and cash equivalents	0.0	99.9
Net Asset Value \| Pooled investment fund measured at NAV
Investment securities, non-current:
Fixed-income mutual fund and Pooled investment fund measured at NAV	$ 12.9	$ 12.9

Amount of liability recognized from contingent consideration in asset acquisition.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 50
-Name Accounting Standards Codification
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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