v3.26.1
Borrowings - Schedule of Components of Interest and Other Debt Expenses (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
2025 Notes        
Debt Instrument [Line Items]        
Coupon interest   $ 0.0   $ 4.2
Amortization of financing costs and discount   0.0   0.5
Effect of interest rate swap   0.0   0.0
Total interest expense   $ 0.0   $ 4.7
Coupon interest rate (net of effect of interest rate swaps)   3.50%   3.50%
2027 Notes        
Debt Instrument [Line Items]        
Coupon interest $ 2.4 $ 2.4 $ 7.1 $ 7.1
Amortization of financing costs and discount 0.2 0.2 0.7 0.7
Effect of interest rate swap 2.6 3.2 8.1 10.1
Total interest expense $ 5.2 $ 5.8 $ 15.9 $ 17.9
Coupon interest rate (net of effect of interest rate swaps) 5.555% 6.28% 5.71% 6.458%
2029 Notes        
Debt Instrument [Line Items]        
Coupon interest $ 5.3 $ 5.3 $ 16.0 $ 16.0
Amortization of financing costs and discount 0.3 0.3 0.9 0.9
Effect of interest rate swap (0.2) 0.3 (0.2) 1.4
Total interest expense $ 5.4 $ 5.9 $ 16.7 $ 18.3
Coupon interest rate (net of effect of interest rate swaps) 6.777% 7.45% 6.941% 7.65%
2030 Notes        
Debt Instrument [Line Items]        
Coupon interest $ 4.7 $ 4.8 $ 14.3 $ 6.6
Amortization of financing costs and discount 0.2 0.2 0.6 0.3
Effect of interest rate swap (0.3) 0.2 (0.6) 0.2
Total interest expense $ 4.6 $ 5.2 $ 14.3 $ 7.1
Coupon interest rate (net of effect of interest rate swaps) 5.858% 6.515% 6.012% 6.514%