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FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Aug. 13, 2021	Mar. 17, 2021	Oct. 22, 2019	Dec. 15, 2016
Operating expenses
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debt other-than-temporary impairments	$ 101.3	$ 0.0	$ 0.0
Senior Notes \| Senior Notes due 2031 – 4.000%
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate (percent)	4.00%	4.00%			4.00%
Senior Notes \| Senior Notes due 2032 – 4.375%
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate (percent)	4.375%	4.375%		4.375%
Senior Notes \| Senior Notes - 4.500%
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate (percent)	4.50%	4.50%				4.50%
Senior Notes \| Senior Notes due 2026 – 5.250%
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate (percent)	5.25%	5.25%					5.25%
Convertible debt investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost basis of investment	$ 225.8	$ 222.1
Unrealized loss on investment	140.0	105.1
Allowance for credit loss	$ 101.3	$ 0.0
Convertible debt investments \| Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt term (in years)	6 years
Convertible debt investments \| Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt term (in years)	3 years 10 months 24 days