Debt - Text (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2025	Sep. 30, 2025
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 665.0
Line of Credit Facility, Maximum Borrowing Capacity	1,000.0
Letter of Credit, Maximum Borrowing Capacity	$ 100.0
Letter of Credit, Maximum Borrowing Capacity, Percentage of Revolving Credit Commitment	50.00%
Long-term Line of Credit	$ 0.0	$ 0.0
Letters of Credit Outstanding, Amount	57.4
Line of Credit Facility, Remaining Borrowing Capacity	607.6
Debt	793.2	802.7
Debt Repurchase Program, Authorized Amount	30.0
Debt Repurchase Authorization Remaining	30.0
Credit Facility Maturing December 18, 2029
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	600.0
Credit Facility Maturing October 28, 2026
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 65.0
Senior Notes 5.0% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.00%
Debt	$ 298.8	298.7
Debt Instrument, Face Amount	$ 300.0
Debt Instrument, Redemption Price, Percentage	100.833%
Debt Instrument, Interest Rate, Effective Percentage	5.20%
Debt Instrument, Maturity Date	Mar. 01, 2028
Senior Notes 5.0% [Member] | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Debt Instrument, Redemption Period, End Date	Mar. 01, 2026
Senior Notes 6.50%
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Debt	$ 494.4	494.1
Debt Instrument, Face Amount	$ 500.0
Debt Instrument, Frequency of Periodic Payment	semiannually
Debt Instrument, Interest Rate, Effective Percentage	6.70%
Debt Instrument, Maturity Date	Mar. 15, 2033
Senior Notes 6.50% | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	106.50%
Debt Instrument, Redemption Price, Maximum Percentage of Principal Amount Redeemed	40.00%
Debt Instrument, Redemption Period, End Date	Mar. 15, 2028
Senior Notes 6.50% | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	103.25%
Debt Instrument, Redemption Price, Maximum Percentage of Principal Amount Redeemed	100.00%
Debt Instrument, Redemption Period, End Date	Mar. 15, 2030
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Net	$ 6.8	7.2
Secured Debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Debt	$ 0.0	$ 9.9
Repayments of Secured Debt	$ 9.9