FAIR VALUE MEASUREMENTS - Summary of Fair Value of Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Aug. 13, 2021	Mar. 17, 2021	Oct. 22, 2019	Dec. 15, 2016
Senior Notes | Senior Notes due 2031 – 4.000%
Liabilities
Interest rate (percent)	4.00%	4.00%			4.00%
Senior Notes | Senior Notes due 2032 – 4.375%
Liabilities
Interest rate (percent)	4.375%	4.375%		4.375%
Senior Notes | Senior Notes - 4.500%
Liabilities
Interest rate (percent)	4.50%	4.50%				4.50%
Senior Notes | Senior Notes due 2026 – 5.250%
Liabilities
Interest rate (percent)	5.25%	5.25%					5.25%
Reported Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes due 2031 – 4.000%
Liabilities
Long-term debt	$ 500.0	$ 500.0
Reported Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes due 2032 – 4.375%
Liabilities
Long-term debt	400.0	400.0
Reported Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes - 4.500%
Liabilities
Long-term debt	450.0	450.0
Reported Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes due 2026 – 5.250%
Liabilities
Long-term debt	250.0	250.0
Reported Value Measurement | Fair value, inputs, level 2 | Receivables facility
Liabilities
Long-term debt	0.0	75.0
Reported Value Measurement | Fair value, inputs, level 2 | Credit Facilities | Revolving loans
Liabilities
Long-term debt	88.3	300.5
Reported Value Measurement | Fair value, inputs, level 2 | Credit Facilities | Term loans
Liabilities
Long-term debt	925.0	975.0
Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes due 2031 – 4.000%
Liabilities
Long-term debt	380.0	350.6
Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes due 2032 – 4.375%
Liabilities
Long-term debt	304.0	284.0
Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes - 4.500%
Liabilities
Long-term debt	366.8	325.7
Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Senior Notes | Senior Notes due 2026 – 5.250%
Liabilities
Long-term debt	233.1	230.0
Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Receivables facility
Liabilities
Long-term debt	0.0	75.0
Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Credit Facilities | Revolving loans
Liabilities
Long-term debt	88.3	300.5
Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Credit Facilities | Term loans
Liabilities
Long-term debt	925.0	975.0
Fair Value, Measurements, Recurring | Reported Value Measurement | Fair value, inputs, level 1
Assets
Cash equivalents	1.2	64.3
Fair Value, Measurements, Recurring | Reported Value Measurement | Fair value, inputs, level 1 | Investment securities in non-qualified retirement plan assets
Assets
Other	36.3	38.4
Fair Value, Measurements, Recurring | Reported Value Measurement | Fair value, inputs, level 2 | Other Long-term Debt
Liabilities
Long-term debt	0.4	12.7
Fair Value, Measurements, Recurring | Reported Value Measurement | Fair value, inputs, level 3 | Convertible debt investments
Assets
Convertible debt investments	85.8	117.0
Fair Value, Measurements, Recurring | Reported Value Measurement | Fair value, inputs, level 3 | Loans receivable
Assets
Other	0.0	32.8
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair value, inputs, level 1
Assets
Cash equivalents	1.2	64.3
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair value, inputs, level 1 | Investment securities in non-qualified retirement plan assets
Assets
Other	36.3	38.4
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair value, inputs, level 2 | Other Long-term Debt
Liabilities
Long-term debt	0.4	12.7
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair value, inputs, level 3 | Convertible debt investments
Assets
Convertible debt investments	85.8	117.0	$ 190.3
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair value, inputs, level 3 | Loans receivable
Assets
Other	$ 0.0	$ 32.8