Borrowings - 2029 Notes (Narrative) (Details) - USD ($) $ in Thousands	Feb. 01, 2024	Jun. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Long-term debt		$ 4,315,465	$ 3,117,719
2029 Notes
Debt Instrument [Line Items]
Debt instrument, face amount	$ 600,000
Long-term debt		$ 600,000
Interest rate	6.00%
Debt instrument, redemption price, percentage	100.00%
2029 Notes | Interest rate swaps
Debt Instrument [Line Items]
Fixed interest rate (as a percent)	6.248%
Notional amount	$ 600,000
2029 Notes | US Treasury (UST) Interest Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.35%
2029 Notes | One-month Secured Overnight Financing Rate (SOFR) | Interest rate swaps
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.444%