Debt - Schedule of Debt Settlement Transaction (Details) - USD ($) $ in Millions	1 Months Ended											12 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Feb. 28, 2025	Dec. 31, 2024	Nov. 30, 2024	Sep. 30, 2024	Feb. 29, 2024	Sep. 30, 2023	Aug. 31, 2023	Jun. 30, 2023	May 31, 2023	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Debt Instrument [Line Items]
Net Loss on Inducements and Settlements												$ 0.0	$ 1.7	$ 12.2
Line of credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Principal Amount Settled		$ 0.0
Total Cash Consideration		0.0
Net Loss on Inducements and Settlements		$ 1.4
Term Loan Facility
Debt Instrument [Line Items]
Principal Amount Settled				$ 750.0
Total Cash Consideration				750.0
Net Loss on Inducements and Settlements				$ 0.3
4.250% 2025 Notes \| Senior indebtedness \| Long-term Debt
Debt Instrument [Line Items]
Principal Amount Settled	$ 1,200.0
Total Cash Consideration	1,200.0
Net Loss on Inducements and Settlements	$ 0.0
2015 Senior Convertible Debt \| Senior subordinated convertible debt
Debt Instrument [Line Items]
Principal Amount Settled			$ 0.4
Total Cash Consideration			0.4
Net Loss on Inducements and Settlements			$ 0.0
2015 Senior Convertible Debt \| Senior subordinated convertible debt \| Long-term Debt
Debt Instrument [Line Items]
Principal Amount Settled											$ 5.6
Total Cash Consideration											18.9
Net Loss on Inducements and Settlements											0.4
2020 Senior Convertible Debt \| Senior subordinated convertible debt
Debt Instrument [Line Items]
Principal Amount Settled					$ 665.5
Total Cash Consideration					665.5
Net Loss on Inducements and Settlements					$ 0.0
0.983% 2024 Notes \| Senior indebtedness
Debt Instrument [Line Items]
Principal Amount Settled						$ 1,000.0
Total Cash Consideration						1,000.0
Net Loss on Inducements and Settlements						$ 0.0
0.972% 2024 Notes \| Senior indebtedness \| Long-term Debt
Debt Instrument [Line Items]
Principal Amount Settled							$ 1,400.0
Total Cash Consideration							1,400.0
Net Loss on Inducements and Settlements							$ 0.0
2.670% 2023 Notes \| Senior indebtedness \| Long-term Debt
Debt Instrument [Line Items]
Principal Amount Settled								$ 1,000.0
Total Cash Consideration								1,000.0
Net Loss on Inducements and Settlements								$ 0.0
2017 Senior Convertible Debt \| Senior subordinated convertible debt \| Long-term Debt
Debt Instrument [Line Items]
Principal Amount Settled									$ 18.2		25.9
Total Cash Consideration									42.7		56.3
Net Loss on Inducements and Settlements									$ 3.1		6.6
4.333% 2023 Notes \| Senior indebtedness \| Long-term Debt
Debt Instrument [Line Items]
Principal Amount Settled										$ 1,000.0
Total Cash Consideration										1,000.0
Net Loss on Inducements and Settlements										$ 0.0
2017 Junior Convertible Debt \| Junior subordinated convertible debt \| Long-term Debt
Debt Instrument [Line Items]
Principal Amount Settled											6.5
Total Cash Consideration											14.9
Net Loss on Inducements and Settlements											$ 2.1