v3.25.2
Borrowings - Narrative (Details) - USD ($)
 3 Months Ended 9 Months Ended
Feb. 27, 2025
Aug. 15, 2023
May 18, 2021
Feb. 25, 2020
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Sep. 30, 2024
Line of Credit Facility [Line Items]                  
Debt instrument, basis spread, variable rate (as a percent)             0.10%    
Credit facilities payable         $ 510,000,000   $ 510,000,000   $ 710,000,000
Deferred financing costs         10,234,000   10,234,000   11,677,000
Fair Value         1,455,883,000   1,455,883,000   1,648,133,000
Interest expense         $ 31,061,000 $ 32,513,000 $ 89,814,000 $ 96,564,000  
Greater Than 1.60x Borrowings Base                  
Line of Credit Facility [Line Items]                  
Debt covenant ratio             1.60    
Interest rate swap | Designated as Hedging Instrument                  
Line of Credit Facility [Line Items]                  
Interest rate (as a percent)     2.70%            
Notional amount     $ 350,000,000            
Secured Overnight Financing Rate (SOFR)                  
Line of Credit Facility [Line Items]                  
Interest rate (as a percent)             1.875%    
Debt instrument, basis spread, variable rate (as a percent)             0.10%    
Secured Overnight Financing Rate (SOFR) | Greater Than 1.60x Borrowings Base                  
Line of Credit Facility [Line Items]                  
Interest rate (as a percent)             1.75%    
Debt instrument, basis spread, variable rate (as a percent)             0.10%    
Secured Overnight Financing Rate (SOFR) | Interest rate swap | Designated as Hedging Instrument                  
Line of Credit Facility [Line Items]                  
Floating interest rate (as a percent)     0.26161%            
Base Rate                  
Line of Credit Facility [Line Items]                  
Interest rate (as a percent)             0.875%    
Base Rate | Greater Than 1.60x Borrowings Base                  
Line of Credit Facility [Line Items]                  
Interest rate (as a percent)             0.75%    
London Interbank Offered Rate (LIBOR) | Interest rate swap | Designated as Hedging Instrument                  
Line of Credit Facility [Line Items]                  
Floating interest rate (as a percent)     1.658%            
2025 Notes                  
Line of Credit Facility [Line Items]                  
Principal amount       $ 300,000,000          
Net proceeds       293,800,000          
Unaccreted discount       2,500,000          
Underwriting commissions       3,000,000          
Offering costs       $ 700,000          
Coupon interest rate (net of effect of interest rate swaps)       3.50% 3.50%   3.50%    
2027 Notes                  
Line of Credit Facility [Line Items]                  
Principal amount     $ 350,000,000   $ 350,000,000.0   $ 350,000,000.0   300,000,000.0
Net proceeds     344,800,000            
Unaccreted discount     1,000,000   $ 300,000   $ 300,000   200,000
Underwriting commissions     3,500,000            
Offering costs     $ 700,000            
Coupon interest rate (net of effect of interest rate swaps)     2.70%   2.70%   2.70%    
Redemption price (as a percent)     100.00%            
2029 Notes                  
Line of Credit Facility [Line Items]                  
Principal amount   $ 300,000,000     $ 300,000,000.0   $ 300,000,000.0   350,000,000.0
Net proceeds   292,900,000              
Unaccreted discount   3,500,000     $ 2,300,000   $ 2,300,000   400,000
Underwriting commissions   3,000,000              
Offering costs   $ 600,000              
Coupon interest rate (net of effect of interest rate swaps)   7.10%     7.10%   7.10%    
Redemption price (as a percent)   100.00%              
2029 Notes | Interest rate swap | Designated as Hedging Instrument                  
Line of Credit Facility [Line Items]                  
Interest rate (as a percent)   7.10%              
Notional amount   $ 300,000,000              
2029 Notes | Secured Overnight Financing Rate (SOFR) | Interest rate swap | Designated as Hedging Instrument                  
Line of Credit Facility [Line Items]                  
Floating interest rate (as a percent)   3.1255%              
2030 Notes                  
Line of Credit Facility [Line Items]                  
Principal amount $ 300,000,000       $ 300,000,000.0   $ 300,000,000.0   300,000,000.0
Net proceeds 296,300,000                
Unaccreted discount 100,000       $ 0   $ 0   2,700,000
Underwriting commissions 3,000,000                
Offering costs $ 700,000                
Coupon interest rate (net of effect of interest rate swaps) 6.34%       6.34%   6.34%    
Redemption price (as a percent) 100.00%                
2030 Notes | Interest rate swap | Designated as Hedging Instrument                  
Line of Credit Facility [Line Items]                  
Interest rate (as a percent)   6.34%              
Notional amount   $ 300,000,000              
2030 Notes | Secured Overnight Financing Rate (SOFR) | Interest rate swap | Designated as Hedging Instrument                  
Line of Credit Facility [Line Items]                  
Floating interest rate (as a percent)   219.20%              
Revolving Credit Facility | Syndicated Facility payable | Line of Credit                  
Line of Credit Facility [Line Items]                  
Borrowing capacity         $ 1,160,000,000   $ 1,160,000,000    
Accordion feature, increase limit         $ 1,500,000,000   $ 1,500,000,000    
Debt instrument, covenant, total assets to total indebtedness, ratio, minimum threshold         1.50   1.50    
Debt instrument, covenant, consolidated EBITDA to consolidated interest expense, ratio, minimum threshold         2.25   2.25    
Credit facilities payable         $ 510,000,000.0   $ 510,000,000.0   430,000,000
Fair value         $ 510,000,000.0   $ 510,000,000.0   430,000,000
Weighted average interest rate (as a percent)         6.533% 7.576% 6.533% 7.576%  
Interest expense inclusive of fees         $ 9,700,000 $ 10,200,000 $ 27,500,000 $ 29,300,000  
Interest expense         $ 700,000   $ 700,000    
Revolving Credit Facility | OSI2 Citibank Facility payable | Line of Credit                  
Line of Credit Facility [Line Items]                  
Credit facilities payable                 280,000,000
Weighted average interest rate (as a percent)         6.741% 8.029% 6.741% 8.029%  
Interest expense inclusive of fees         $ 4,500,000 $ 6,100,000 $ 14,400,000 $ 18,100,000  
Deferred financing costs         $ 3,100,000   $ 3,100,000    
Fair Value                 $ 280,000,000