Debt - Unamortized Discount and Debt Issuance Costs (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 07, 2024	Mar. 31, 2023
Debt Instrument [Line Items]
Total unamortized discount	$ (13.9)		$ (10.4)
Total debt issuance costs	(5.5)		(16.3)
Senior Indebtedness | 4.333% 2023 Notes
Debt Instrument [Line Items]
Total unamortized discount	0.0		(0.2)
Total debt issuance costs	0.0		(0.4)
Senior Indebtedness | 2.670% 2023 Notes
Debt Instrument [Line Items]
Total unamortized discount	0.0		(0.4)
Total debt issuance costs	0.0		(0.2)
Senior Indebtedness | 0.972% 2024 Notes
Debt Instrument [Line Items]
Total unamortized discount	0.0		(1.2)
Total debt issuance costs	0.0		(0.6)
Senior Indebtedness | 0.983% 2024 Notes
Debt Instrument [Line Items]
Total unamortized discount	(0.4)		(1.3)
Total debt issuance costs	(0.2)		(0.8)
Senior Indebtedness | 4.250% 2025 Notes
Debt Instrument [Line Items]
Total unamortized discount	(4.4)		(7.3)
Total debt issuance costs	(0.6)		(0.9)
Senior Indebtedness | 5.050% 2029 Notes
Debt Instrument [Line Items]
Total unamortized discount	(5.2)	$ (5.3)	0.0
Total debt issuance costs	(2.2)		0.0
Senior Convertible Debt | 2017 Senior Convertible Debt
Debt Instrument [Line Items]
Total debt issuance costs	(0.1)		(0.4)
Senior Convertible Debt | 2020 Senior Convertible Debt
Debt Instrument [Line Items]
Total debt issuance costs	(1.7)		(4.4)
Commercial Paper
Debt Instrument [Line Items]
Total unamortized discount	(3.9)		0.0
Term Loan Facility
Debt Instrument [Line Items]
Total debt issuance costs	(0.7)		0.0
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Total debt issuance costs	$ 0.0		$ (8.6)