Fair Value of Financial Instruments - Summary of Unobservable Inputs and Ranges (Details) - Level 3
$ in Thousands

Mar. 31, 2026

USD ($)

Sep. 30, 2025

USD ($)

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 2,492,286

$ 2,729,010

Long-Term Credit Facility | Market Comparable | Market Yield

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 328,333

$ 683,837

Range of Input

0.055

^[1]

0.048

^[2]

Subordinated Debt | Market Comparable | Market Yield

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 14,528

Range of Input

^[1]

0.155

Subordinated Debt | Market Comparable | Market Yield | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[1]

0.12

Subordinated Debt | Market Comparable | Market Yield | Maximum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[1]

0.25

Subordinated Debt | Enterprise Market Value | EBITDA Multiple

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 4,285

Subordinated Debt | Enterprise Market Value | EBITDA Multiple | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[1]

0.075

Subordinated Debt | Enterprise Market Value | EBITDA Multiple | Maximum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[1]

0.262

Subordinated Debt | Enterprise Market Value | EBITDA Multiple | Weighted Average

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[1]

0.243

First lien | Market Comparable | Broker/Dealer Bids or Quotes

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 92,244

$ 114,625

First lien | Market Comparable | Market Yield

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 2,092,114

$ 2,377,201

First lien | Market Comparable | Market Yield | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

0.07

^[1]

0.04

^[2]

First lien | Market Comparable | Market Yield | Maximum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

0.201

^[1]

0.245

^[2]

First lien | Market Comparable | Market Yield | Weighted Average

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

0.096

^[1]

0.099

^[2]

First lien | Market Comparable | EBITDA Multiple | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[2]

0.083

First lien | Market Comparable | Revenue Multiple

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 3,836

Range of Input

^[1]

0.009

First lien | Market Comparable | Revenue Multiple | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[2]

0.006

First lien | Enterprise Market Value | EBITDA Multiple

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 62,964

$ 17,969

Range of Input

^[1]

0.132

First lien | Enterprise Market Value | EBITDA Multiple | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[1]

0.065

First lien | Enterprise Market Value | EBITDA Multiple | Maximum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[1]

0.179

First lien | Enterprise Market Value | Revenue Multiple

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 4,806

Second lien | Market Comparable | Broker/Dealer Bids or Quotes

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

995

Second lien | Market Comparable | Market Yield

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 17,439

Range of Input

^[2]

0.171

Second lien | Market Comparable | Market Yield | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[2]

0.07

Second lien | Market Comparable | Market Yield | Maximum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

^[2]

0.254

Second lien | Enterprise Market Value | EBITDA Multiple

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 547

Range of Input

^[2]

0.148

Equity | Enterprise Market Value | EBITDA Multiple

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Fair value

$ 221,345

$ 196,398

Equity | Enterprise Market Value | EBITDA Multiple | Minimum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

0.013

^[1]

0.006

^[2]

Equity | Enterprise Market Value | EBITDA Multiple | Maximum

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

0.28

^[1]

0.283

^[2]

Equity | Enterprise Market Value | EBITDA Multiple | Weighted Average

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Range of Input

0.144

^[1]

0.108

^[2]

[1]	The weighted averages disclosed in the table above were weighted by their relative fair value.
[2]	The weighted averages disclosed in the table above were weighted by their relative fair value.