Portfolio Investments - Schedule of Roll-Forward in the Changes in Fair Value (Details) - USD ($)
$ in Thousands |
3 Months Ended |
9 Months Ended |
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Fair value, beginning balance |
$ 2,503,449
|
$ 2,552,861
|
$ 2,477,378
|
$ 2,723,732
|
| Purchases |
215,011
|
140,665
|
583,223
|
567,786
|
| Sales and repayments |
(180,875)
|
(221,661)
|
(474,452)
|
(682,652)
|
| Transfers in |
13,046
|
7,617
|
14,934
|
17,281
|
| Transfers out |
(41,212)
|
(19,490)
|
(43,100)
|
(85,119)
|
| Capitalized PIK interest income |
4,752
|
5,070
|
12,406
|
15,359
|
| Accretion of OID |
2,505
|
3,798
|
7,845
|
11,106
|
| Fair value, ending balance |
2,508,878
|
2,485,322
|
2,508,878
|
2,485,322
|
| Net unrealized appreciation (depreciation) relating to Level 3 investments still held and reported within net unrealized appreciation (depreciation) in the Consolidated Statement of Operations |
$ (11,224)
|
$ 15,018
|
$ (75,594)
|
$ (92,908)
|
| Unrealized gain (loss), location |
Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax
|
Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax
|
Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax
|
Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax
|
| Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
$ (49,169)
|
$ (1,230)
|
$ (57,897)
|
$ (17,651)
|
| Gain (loss), location |
Realized gain (loss)
|
Realized gain (loss)
|
Realized gain (loss)
|
Realized gain (loss)
|
| Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
$ 41,371
|
$ 17,692
|
$ (11,459)
|
$ (64,520)
|
| Gain (loss), location |
Net unrealized appreciation (depreciation)
|
Net unrealized appreciation (depreciation)
|
Net unrealized appreciation (depreciation)
|
Net unrealized appreciation (depreciation)
|
| Senior secured debt |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Fair value, beginning balance |
$ 2,139,293
|
$ 2,165,740
|
$ 2,107,306
|
$ 2,320,310
|
| Purchases |
193,131
|
140,532
|
516,267
|
564,070
|
| Sales and repayments |
(162,528)
|
(219,233)
|
(420,365)
|
(679,251)
|
| Transfers in |
0
|
0
|
0
|
6,555
|
| Transfers out |
(13,046)
|
(19,080)
|
(14,934)
|
(84,709)
|
| Capitalized PIK interest income |
3,179
|
4,357
|
8,992
|
13,258
|
| Accretion of OID |
2,079
|
3,377
|
6,694
|
9,911
|
| Fair value, ending balance |
2,160,672
|
2,076,845
|
2,160,672
|
2,076,845
|
| Net unrealized appreciation (depreciation) relating to Level 3 investments still held and reported within net unrealized appreciation (depreciation) in the Consolidated Statement of Operations |
(2,924)
|
(183)
|
(42,785)
|
(84,243)
|
| Investment exchanged, cost |
13,000
|
7,200
|
13,800
|
30,900
|
| Senior secured debt | Level 2 |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Transfers out |
|
(11,900)
|
|
|
| Senior secured debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
(33,588)
|
(740)
|
(49,417)
|
(16,286)
|
| Senior secured debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
32,152
|
1,892
|
6,129
|
(57,013)
|
| Subordinated debt |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Fair value, beginning balance |
262,217
|
256,925
|
231,137
|
255,346
|
| Purchases |
21,844
|
0
|
66,920
|
3,583
|
| Sales and repayments |
(14,457)
|
(64)
|
(25,284)
|
(229)
|
| Transfers in |
0
|
0
|
0
|
0
|
| Transfers out |
(28,166)
|
0
|
(28,166)
|
0
|
| Capitalized PIK interest income |
1,573
|
713
|
3,058
|
2,101
|
| Accretion of OID |
426
|
421
|
1,151
|
1,195
|
| Fair value, ending balance |
242,777
|
257,498
|
242,777
|
257,498
|
| Net unrealized appreciation (depreciation) relating to Level 3 investments still held and reported within net unrealized appreciation (depreciation) in the Consolidated Statement of Operations |
(704)
|
(497)
|
(6,108)
|
(4,498)
|
| Investment exchanged, cost |
28,200
|
|
28,200
|
|
| Subordinated debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
44
|
0
|
69
|
0
|
| Subordinated debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
(704)
|
(497)
|
(6,108)
|
(4,498)
|
| Preferred equity |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Fair value, beginning balance |
48,974
|
70,147
|
72,122
|
66,320
|
| Purchases |
0
|
109
|
0
|
109
|
| Sales and repayments |
(826)
|
0
|
(25,572)
|
(587)
|
| Transfers in |
0
|
410
|
1,167
|
1,056
|
| Transfers out |
0
|
0
|
0
|
0
|
| Capitalized PIK interest income |
0
|
0
|
356
|
0
|
| Accretion of OID |
0
|
0
|
0
|
0
|
| Fair value, ending balance |
48,866
|
73,232
|
48,866
|
73,232
|
| Net unrealized appreciation (depreciation) relating to Level 3 investments still held and reported within net unrealized appreciation (depreciation) in the Consolidated Statement of Operations |
720
|
2,559
|
(5,961)
|
6,342
|
| Investment exchanged, cost |
|
400
|
1,200
|
600
|
| Preferred equity | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
(155)
|
0
|
6,754
|
(663)
|
| Preferred equity | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
873
|
2,566
|
(5,961)
|
6,997
|
| Common equity and warrants |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Fair value, beginning balance |
52,965
|
60,049
|
66,813
|
81,756
|
| Purchases |
36
|
24
|
36
|
24
|
| Sales and repayments |
(3,064)
|
(2,364)
|
(3,231)
|
(2,585)
|
| Transfers in |
13,046
|
7,207
|
13,767
|
9,670
|
| Transfers out |
0
|
(410)
|
0
|
(410)
|
| Capitalized PIK interest income |
0
|
0
|
0
|
0
|
| Accretion of OID |
0
|
0
|
0
|
0
|
| Fair value, ending balance |
56,563
|
77,747
|
56,563
|
77,747
|
| Net unrealized appreciation (depreciation) relating to Level 3 investments still held and reported within net unrealized appreciation (depreciation) in the Consolidated Statement of Operations |
(8,316)
|
13,139
|
(20,740)
|
(10,509)
|
| Investment exchanged, cost |
|
|
|
9,700
|
| Common equity and warrants | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
(15,470)
|
(490)
|
(15,303)
|
(702)
|
| Common equity and warrants | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Total gains or losses included in earnings |
$ 9,050
|
$ 13,731
|
$ (5,519)
|
(10,006)
|
| Investment, Change in Market Quotes or Liquidity |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Transfers in |
|
|
|
6,600
|
| Transfers out |
|
|
|
(43,500)
|
| Common Stock |
|
|
|
|
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |
|
|
|
|
| Investment exchanged, cost |
|
|
|
$ 400
|