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INVESTMENTS - Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Mar. 31, 2024 | Mar. 31, 2023 | Oct. 31, 2023 | Sep. 30, 2022 | Aug. 31, 2022 | Mar. 31, 2022 | Aug. 31, 2012
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Cost | $ 854,290 | [1] | $ 720,630 | [2] |  |  |  |  |
Fair value | 920,504 | [1] | 753,543 | [2] |  |  |  |  |
Horizon Facilities Services, Inc. |  |  |  |  |  |  |  |  |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Realized gain (loss) on preferred equity |  |  | 12,300 |  |  |  |  |  |
SFEG Holdings, Inc |  |  |  |  |  |  |  |  |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Cost |  |  |  |  | $ 4,800 |  |  |  |
Fair value |  |  |  |  | $ 8,600 |  |  |  |
Ginsey Home Solutions, Inc. |  |  |  |  |  |  |  |  |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Cost |  |  |  |  |  |  | $ 12,200 |  | $ 5,000
Fair value |  |  |  |  |  |  | $ 12,200 |  |
PSI Molded Plastics, Inc |  |  |  |  |  |  |  |  |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Cost |  |  |  |  |  | $ 26,600 |  |  |
Fair value |  |  |  |  |  | $ 26,600 |  |  |
Total |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Beginning balance | 920,486 |  | 753,516 |  |  |  |  | $ 714,322 |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Issuances / originations | 183,924 |  | 133,768 |  |  |  |  |  |
Settlements / repayments | (28,000) |  | (57,396) |  |  |  |  |  |
Sales | (52,228) |  | (35,758) |  |  |  |  |  |
Transfers | 0 |  | 0 |  |  |  |  |  |
Ending balance | 920,486 |  | 753,516 |  |  |  |  |  |
Total | Debt and Equity Securities, Realized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | 29,964 |  | 10,778 |  |  |  |  |  |
Total | Debt and Equity Securities, Unrealized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | 62,319 |  | (9,949) |  |  |  |  |  |
Reversal of previously recorded (appreciation) depreciation upon realization | (29,009) |  | (2,249) |  |  |  |  |  |
Secured First Lien Debt |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Beginning balance | 474,856 |  | 437,517 |  |  |  |  | 425,087 |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Issuances / originations | 74,536 |  | 107,200 |  |  |  |  |  |
Settlements / repayments | (28,000) |  | (50,800) |  |  |  |  |  |
Sales | 0 |  | 0 |  |  |  |  |  |
Transfers | 0 |  | (14,418) |  |  |  |  |  |
Ending balance | 474,856 |  | 437,517 |  |  |  |  |  |
Secured First Lien Debt | Debt and Equity Securities, Realized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | (4,550) |  | 0 |  |  |  |  |  |
Secured First Lien Debt | Debt and Equity Securities, Unrealized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | (7,859) |  | (29,552) |  |  |  |  |  |
Reversal of previously recorded (appreciation) depreciation upon realization | 3,212 |  | 0 |  |  |  |  |  |
Secured Second Lien Debt |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Beginning balance | 138,703 |  | 75,734 |  |  |  |  | 67,958 |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Issuances / originations | 64,000 |  | 5,188 |  |  |  |  |  |
Settlements / repayments | 0 |  | (6,596) |  |  |  |  |  |
Sales | 0 |  | 0 |  |  |  |  |  |
Transfers | 0 |  | 14,418 |  |  |  |  |  |
Ending balance | 138,703 |  | 75,734 |  |  |  |  |  |
Secured Second Lien Debt | Debt and Equity Securities, Realized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | (3,200) |  | (10,000) |  |  |  |  |  |
Secured Second Lien Debt | Debt and Equity Securities, Unrealized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | (1,031) |  | (5,235) |  |  |  |  |  |
Reversal of previously recorded (appreciation) depreciation upon realization | 3,200 |  | 10,001 |  |  |  |  |  |
Preferred Equity |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Beginning balance | 213,480 |  | 222,585 |  |  |  |  | 217,599 |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Issuances / originations | 14,688 |  | 21,000 |  |  |  |  |  |
Settlements / repayments | 0 |  | 0 |  |  |  |  |  |
Sales | (50,726) |  | (35,758) |  |  |  |  |  |
Transfers | (8,621) |  | 0 |  |  |  |  |  |
Ending balance | 213,480 |  | 222,585 |  |  |  |  |  |
Preferred Equity | Debt and Equity Securities, Realized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | 36,833 |  | 20,778 |  |  |  |  |  |
Preferred Equity | Debt and Equity Securities, Unrealized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | 34,050 |  | 11,216 |  |  |  |  |  |
Reversal of previously recorded (appreciation) depreciation upon realization | (35,329) |  | (12,250) |  |  |  |  |  |
Common Equity/ Equivalents |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Beginning balance | 93,447 |  | 17,680 |  |  |  |  | $ 3,678 |
New investments, repayments and settlements: |  |  |  |  |  |  |  |  |
Issuances / originations | 30,700 |  | 380 |  |  |  |  |  |
Settlements / repayments | 0 |  | 0 |  |  |  |  |  |
Sales | (1,502) |  | 0 |  |  |  |  |  |
Transfers | 8,621 |  | 0 |  |  |  |  |  |
Ending balance | 93,447 |  | 17,680 |  |  |  |  |  |
Common Equity/ Equivalents | Debt and Equity Securities, Realized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | 881 |  | 0 |  |  |  |  |  |
Common Equity/ Equivalents | Debt and Equity Securities, Unrealized Gain (Loss) |  |  |  |  |  |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |  |  |  |  |  |
Total gain (loss) | 37,159 |  | 13,622 |  |  |  |  |  |
Reversal of previously recorded (appreciation) depreciation upon realization | $ (92) |  | $ 0 |  |  |  |  |  |
[1] | Cumulative gross unrealized appreciation for federal income tax purposes is $180.5 million; cumulative gross unrealized depreciation for federal income tax purposes is $115.8 million. Cumulative net unrealized appreciation is $64.7 million, based on a tax cost of $855.8 million.
[2] | Cumulative gross unrealized appreciation for federal income tax purposes is $150.4 million; cumulative gross unrealized depreciation for federal income tax purposes is $119.3 million. Cumulative net unrealized appreciation is $31.1 million, based on a tax cost of $722.4 million.

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