Borrowings - Adviser Revolver (Narrative) (Details) - USD ($) |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
Sep. 30, 2024 |
|
| Debt Instrument [Line Items] | |||||
| Long-term debt | $ 5,127,148,000 | $ 5,127,148,000 | $ 4,599,430,000 | ||
| Average stated interest rate | 5.90% | ||||
| Adviser Revolver | Line of Credit | |||||
| Debt Instrument [Line Items] | |||||
| Long-term debt | 0 | $ 0 | 0 | ||
| Other Short-Term Borrowings | |||||
| Debt Instrument [Line Items] | |||||
| Short-term debt, average outstanding amount | $ 4,962,538,000 | $ 3,351,951,000 | 4,867,651,000 | $ 3,211,972,000 | |
| Average stated interest rate | 5.70% | 6.50% | 5.90% | ||
| Revolving Credit Facility | Adviser Revolver | Line of Credit | |||||
| Debt Instrument [Line Items] | |||||
| Line of credit facility, maximum borrowing capacity | $ 300,000,000 | $ 300,000,000 | $ 200,000,000 | ||
| Interest rate | 4.00% | 4.00% | |||
| X | ||||||||||
- Definition The average effective interest rate during the reporting period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Contractual interest rate for funds borrowed, under the debt agreement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|