Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities at Fair Value

The Company’s financial assets and liabilities accounted for at fair value on a recurring basis are summarized below by level within the fair value hierarchy:

	As of September 30, 2024
(In millions)	Total		Level 1		Level 2		Level 3		NAV (a)
Cash and cash equivalents
Money market funds	$	0.3	$	0.3	$	—	$	—	$	—
Time deposits	2.6		—		2.6		—		—
Other noncurrent assets
Non-qualified trust funds	1.9		—		—		—		1.9
Deferred compensation investments	23.0		23.0		—		—		—
Total assets at fair value	$	27.8	$	23.3	$	2.6	$	—	$	1.9
Other noncurrent liabilities
Deferred compensation obligations	22.3		—		—		—		22.3
Total liabilities at fair value	$	22.3	$	—	$	—	$	—	$	22.3

	As of September 30, 2023
(In millions)	Total		Level 1		Level 2		Level 3		NAV (a)
Cash and cash equivalents
Money market funds	$	0.6	$	0.6	$	—	$	—	$	—
Time deposits	277.3		—		277.3		—		—
Prepaid expenses and other current assets
Currency derivatives	0.1		—		0.1		—		—
Interest rate swap agreements	7.8		—		7.8		—		—
Other noncurrent assets
Non-qualified trust funds	2.1		—		—		—		2.1
Deferred compensation investments	19.0		19.0		—		—		—
Total assets at fair value	$	306.9	$	19.6	$	285.2	$	—	$	2.1
Accrued expenses and other liabilities
Currency derivatives	$	0.1	$	—	$	0.1	$	—	$	—
Other noncurrent liabilities
Deferred compensation obligations	20.8		—		—		—		20.8
Total liabilities at fair value	$	20.9	$	—	$	0.1	$	—	$	20.8

(a)Funds measured at fair value using the NAV per share practical expedient have not been classified in the fair value hierarchy.

Schedule of Fair Value of Investments

The fair value of these investments summarized below is determined utilizing quoted prices for identical securities from less active markets, which are considered Level 2 inputs within the fair value hierarchy.

	September 30, 2023
(In millions)	Amortized cost		Gross unrealized losses		Fair value
Cash and cash equivalents
U.S. treasuries (a)	$	2.2	$	—	$	2.2
Short-term investments
U.S. treasuries (b)	$	347.5	$	(0.5)	$	347.0

(a)U.S. treasury securities with original maturity dates of three months or less.

(b)U.S. treasury securities with original maturities greater than three months and less than 12 months.

Summary of Fair Value of Debt

The fair values of the Company's outstanding fixed rate senior notes shown in the table below are based on recent trading values, which are considered Level 2 inputs within the fair value hierarchy.

	September 30, 2024						September 30, 2023
(In millions)	Fair value		Carrying value (a)		Unamortized discounts and issuance costs		Fair value		Carrying value (a)		Unamortized discounts and issuance costs
2030 Notes	$	—	$	—	$	—	$	589.8	$	594.5	$	(5.5)
2031 Notes	478.5		530.4		(4.6)		416.6		529.9		(5.2)
Total	$	478.5	$	530.4	$	(4.6)	$	1,006.4	$	1,124.4	$	(10.7)

(a)Carrying values shown are net of unamortized discounts and issuance costs.