v3.26.1
Debt - Text (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2026
Sep. 30, 2025
Debt Instrument [Line Items]        
Line of Credit Facility, Current Borrowing Capacity $ 715.0   $ 715.0  
Line of Credit Facility, Maximum Borrowing Capacity 1,000.0   1,000.0  
Letter of Credit, Maximum Borrowing Capacity $ 100.0   $ 100.0  
Letter of Credit, Maximum Borrowing Capacity, Percentage of Revolving Credit Commitment 50.00%   50.00%  
Long-term Line of Credit $ 0.0   $ 0.0 $ 0.0
Letters of Credit Outstanding, Amount 42.9   42.9  
Line of Credit Facility, Remaining Borrowing Capacity 672.1   672.1  
Debt 793.5   793.5 802.7
Debt Repurchase Program, Authorized Amount 30.0   30.0  
Debt Repurchase Authorization Remaining 30.0   30.0  
Credit Facility Maturing December 18, 2029        
Debt Instrument [Line Items]        
Line of Credit Facility, Current Borrowing Capacity 650.0   650.0  
Line of Credit Facility, Increase (Decrease), Net 50.0 $ 25.0    
Credit Facility Maturing October 28, 2026        
Debt Instrument [Line Items]        
Line of Credit Facility, Current Borrowing Capacity $ 65.0   $ 65.0  
Senior Notes 5.0% [Member]        
Debt Instrument [Line Items]        
Debt Instrument, Interest Rate, Stated Percentage 5.00%   5.00%  
Debt $ 298.9   $ 298.9 298.7
Debt Instrument, Face Amount $ 300.0   $ 300.0  
Debt Instrument, Interest Rate, Effective Percentage 5.20%   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%   6.50%  
Debt $ 494.6   $ 494.6 494.1
Debt Instrument, Face Amount $ 500.0   $ 500.0  
Debt Instrument, Frequency of Periodic Payment     semiannually  
Debt Instrument, Interest Rate, Effective Percentage 6.70%   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  
Secured Debt        
Debt Instrument [Line Items]        
Debt Instrument, Interest Rate, Stated Percentage   4.00%    
Debt $ 0.0   $ 0.0 9.9
Repayments of Secured Debt   $ 9.9    
Senior Notes [Member]        
Debt Instrument [Line Items]        
Debt Issuance Costs, Net $ 6.5   $ 6.5 $ 7.2