FINANCIAL HIGHLIGHTS (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2024 |
Mar. 31, 2023 |
Mar. 31, 2022 |
Mar. 31, 2021 |
Mar. 31, 2020 |
Mar. 31, 2019 |
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Investment Company, Financial Highlights [Roll Forward] | ||||||||||
| Net asset value at beginning of period (in USD per share) | $ 13.55 | $ 13.43 | $ 13.09 | $ 13.43 | $ 11.52 | $ 11.17 | $ 12.40 | $ 10.85 | $ 9.95 | $ 9.22 |
| (Loss) income from investment operations | ||||||||||
| Net investment (loss) income, basic (in USD per share) | (0.10) | 0.76 | 0.63 | 1.11 | 0.45 | 0.54 | 1.11 | 0.23 | 0.68 | 0.74 |
| Net realized (loss) gain on investments and other (in USD per share) | (0.71) | 1.72 | 0.88 | 0.32 | 0.37 | 0.32 | 1.36 | 2.04 | 0.04 | 0.51 |
| Taxes on deemed distributions of long-term capital gains (in USD per share) | 0 | 0 | 0 | 0 | 0 | 0 | (0.31) | (0.41) | 0 | 0 |
| Net unrealized appreciation (depreciation) of investments and other (in USD per share) | 5.58 | (0.70) | 0.96 | (0.36) | 2.26 | 0.42 | (2.38) | 0.63 | 1.16 | 0.23 |
| Total from investment operations (in USD per share) | 4.77 | 1.78 | 2.47 | 1.07 | 3.08 | 1.28 | (0.22) | 2.49 | 1.88 | 1.48 |
| Effect of equity capital activity | ||||||||||
| Cash distributions to common stockholders from net investment income (in USD per share) | (0.99) | (0.64) | (1.08) | (0.92) | (0.91) | (0.83) | (0.75) | (0.69) | (0.84) | (0.75) |
| Cash distributions to common stockholders from net realized gains (in USD per share) | (0.51) | (1.02) | (1.12) | (0.49) | (0.26) | (0.10) | (0.28) | (0.24) | (0.05) | 0 |
| Discounts, commissions, and offering costs par share (in USD per share) | (0.02) | 0 | (0.02) | (0.01) | 0 | 0 | 0 | 0 | (0.03) | 0 |
| Net accretive (dilutive) effect of equity offering (in USD per share) | 0.07 | 0 | 0.10 | 0.01 | 0 | 0 | 0.01 | 0 | (0.04) | 0 |
| Total from equity capital activity (in USD per share) | (1.45) | (1.66) | (2.12) | (1.41) | (1.17) | (0.93) | (1.02) | (0.93) | (0.96) | (0.75) |
| Other, net (in USD per share) | (0.09) | 0 | (0.01) | 0 | 0 | 0 | 0.01 | (0.01) | (0.02) | 0 |
| Net asset value at end of period (in USD per share) | 16.78 | 13.55 | 13.43 | 13.09 | 13.43 | 11.52 | 11.17 | 12.40 | 10.85 | 9.95 |
| Per common share market value at beginning of period (in USD per share) | 13.36 | 14.23 | 13.25 | 16.13 | 12.23 | 7.85 | 11.60 | 10.10 | 9.07 | 7.02 |
| Per common share market value at end of period (in USD per share) | $ 14.20 | $ 13.36 | $ 14.23 | $ 13.25 | $ 16.13 | $ 12.23 | $ 7.85 | $ 11.60 | $ 10.10 | $ 9.07 |
| Total investment return | 18.14% | 5.65% | 25.52% | (8.90%) | 42.40% | 70.65% | (26.23%) | 24.95% | 21.82% | 41.58% |
| Common stock outstanding at end of period (in shares) | 39,821,967 | 36,837,381 | 36,688,667 | 33,591,505 | 33,205,023 | 33,205,023 | 33,049,463 | 32,822,459 | 32,653,635 | 30,270,958 |
| Weighted-average shares of common stock outstanding - basic (in shares) | 38,712,611 | 36,735,218 | 34,466,724 | 33,311,785 | 33,205,023 | 33,176,760 | 32,865,840 | 32,807,597 | 32,268,776 | 30,270,958 |
| Weighted-average shares of common stock outstanding - diluted (in shares) | 38,712,611 | 36,735,218 | 34,466,724 | 33,311,785 | 33,205,023 | 33,176,760 | 32,865,840 | 32,807,597 | 32,268,776 | 30,270,958 |
| Consolidated Statement of Assets and Liabilities Data: | ||||||||||
| Net assets at end of year | $ 668,225 | $ 499,084 | $ 492,711 | $ 439,742 | $ 445,830 | $ 382,364 | $ 369,031 | $ 407,110 | $ 354,200 | $ 301,082 |
| Average net assets | 545,378 | 478,440 | 461,819 | 446,899 | 425,985 | 365,568 | 404,336 | 391,786 | 328,533 | 294,030 |
| Senior Securities Data: | ||||||||||
| Total borrowings, at cost | 572,888 | 463,738 | 404,238 | 297,688 | 267,584 | 155,434 | 54,296 | 58,096 | 112,096 | 74,796 |
| Mandatorily redeemable preferred stock | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 94,371 | $ 132,250 | $ 132,250 | $ 139,150 | $ 139,150 |
| Ratios/Supplemental Data: | ||||||||||
| Ratio of net expenses to average net assets | 18.85% | 13.70% | 14.19% | 9.97% | 13.51% | 10.58% | 6.32% | 13.30% | 11.08% | 10.02% |
| Ratio of net investment (loss) income to average net assets | (0.69%) | 5.87% | 4.72% | 8.28% | 3.52% | 4.91% | 8.99% | 1.92% | 6.68% | 7.63% |
| Portfolio turnover ratio | 1.68% | 20.41% | 9.58% | 12.45% | 12.34% | 8.99% | 21.27% | 17.16% | 14.87% | 13.86% |
| Ratio of expenses to average net assets - annualized | 22.02% | 16.79% | 17.38% | 12.58% | 16.72% | 13.33% | 9.12% | 16.45% | 14.11% | 13.46% |
| Ratio of net expenses to average net assets | 6.89% | 14.07% | ||||||||
| Ratio of net investment (loss) income to average net assets – annualized | (3.85%) | 2.79% | 1.53% | 5.66% | 0.31% | 2.16% | 6.20% | (1.22%) | 3.66% | 4.19% |