FINANCIAL HIGHLIGHTS (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|||||
| Investment Company, Financial Highlights [Roll Forward] | ||||||||||||||
| NAV as of the beginning of the period (in dollars per share) | $ 15.54 | [1] | $ 15.22 | $ 15.36 | $ 14.56 | $ 15.54 | $ 15.92 | $ 16.29 | $ 16.29 | $ 15.76 | $ 16.80 | |||
| Net investment income (in dollars per share) | 1.43 | 1.44 | 1.32 | 1.34 | 1.18 | 1.42 | 1.48 | 1.46 | 1.40 | 1.50 | ||||
| Net realized gain (loss) (in dollars per share) | 0.39 | (0.85) | (0.10) | (0.07) | (1.32) | (0.47) | (0.46) | (0.06) | (0.58) | (0.22) | ||||
| Net unrealized appreciation (depreciation) (in dollars per share) | (0.38) | 1.16 | (0.04) | 0.62 | (0.08) | 0.08 | 0 | (0.04) | 1.12 | (1.56) | ||||
| Income tax provision (in dollars per share) | (0.03) | (0.10) | (0.04) | (0.05) | (0.03) | (0.02) | 0 | 0 | 0 | 0 | ||||
| Net increase (decrease) in net assets resulting from operations (in dollars per share) | 1.41 | 1.65 | 1.14 | 1.84 | (0.25) | 1.01 | 1.02 | 1.36 | 1.94 | (0.28) | ||||
| Dividends paid from net investment income (in dollars per share) | (1.10) | (1.40) | (1.29) | (1.05) | (0.70) | (1.35) | (1.40) | (1.40) | (1.40) | (1.40) | ||||
| Distributions paid from capital gains (in dollars per share) | (0.35) | 0 | 0 | 0 | 0 | (0.05) | 0 | 0 | 0 | 0 | ||||
| Distributions paid or accrued (in dollars per share) | (1.45) | (1.40) | (1.29) | (1.05) | (0.70) | (1.40) | (1.40) | (1.40) | (1.40) | (1.40) | ||||
| Accretive effect of stock repurchases (repurchasing shares below NAV) (in dollars per share) | 0.01 | 0.06 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||||
| Other (in dollars per share) | 0.02 | 0.01 | 0.01 | 0.01 | (0.03) | 0.01 | 0.01 | 0.04 | (0.01) | 0.64 | ||||
| NAV as of the ending of the period (in dollars per share) | $ 15.53 | [1] | $ 15.54 | [1] | $ 15.22 | $ 15.36 | $ 14.56 | $ 15.54 | $ 15.92 | $ 16.29 | $ 16.29 | $ 15.76 | ||
| Shares outstanding as of the end of the period (in shares) | 40,240,358 | 40,054,433 | 40,053,000 | 39,913,303 | 39,804,152 | 39,231,689 | 39,292,412 | 39,755,866 | 36,691,486 | 31,191,022 | ||||
| NAV as of the end of the period | $ 624,903 | [1] | $ 622,307 | [1] | $ 609,665 | $ 613,170 | $ 579,624 | $ 609,305 | $ 625,366 | $ 647,789 | $ 597,833 | $ 491,652 | ||
| Average NAV | 621,478 | 613,525 | 611,214 | 593,440 | 557,382 | 622,708 | 642,625 | 629,775 | 535,175 | 400,045 | ||||
| Average outstanding debt | $ 524,380 | $ 487,271 | $ 494,957 | $ 321,973 | $ 386,084 | $ 474,000 | $ 482,200 | $ 427,200 | $ 396,000 | $ 304,973 | ||||
| Ratios to average NAV: | ||||||||||||||
| Ratio of total expenses, including income tax expense, to average NAV (as a percent) | 12.65% | 12.63% | 8.60% | 6.51% | 7.38% | 9.11% | 9.11% | 7.88% | 7.56% | 8.27% | ||||
| Ratio of operating expenses to average NAV (as a percent) | 12.47% | 12.02% | 8.33% | 6.20% | 7.16% | 9.11% | 8.95% | 7.78% | 7.50% | 8.24% | ||||
| Ratio of operating expenses excluding interest expense, to average NAV (as a percent) | 6.19% | 6.07% | 4.33% | 3.76% | 4.07% | 4.86% | 5.09% | 4.87% | 4.69% | 5.45% | ||||
| Ratio of operating expenses, excluding interest expense and incentive fees to average NAV (as a percent) | 4.18% | 4.02% | 3.98% | 3.66% | 4.07% | 4.22% | 4.57% | 4.61% | 4.68% | 4.91% | ||||
| Ratio of net investment income to average NAV (as a percent) | 9.22% | 9.40% | 8.65% | 8.99% | 8.40% | 8.84% | 9.16% | 9.01% | 8.91% | 9.01% | ||||
| Portfolio turnover ratio (as a percent) | 22.69% | 21.82% | 18.92% | 35.39% | 8.93% | 33.30% | 45.06% | 50.66% | 39.01% | 24.23% | ||||
| Total return based on change in NAV (as a percent) | 9.77% | 10.86% | 7.43% | 12.71% | (1.80%) | 6.41% | 6.26% | 8.59% | 12.31% | 2.14% | ||||
| Expense waivers | $ 9,500 | $ 8,300 | $ 4,500 | $ 4,300 | $ 3,600 | $ 3,100 | $ 6,000 | $ 4,600 | $ 4,000 | $ 4,600 | ||||
| Investment Company, Ratio To Average Net Assets Excluding Expense Waivers | ||||||||||||||
| Ratio of total expenses, including income tax expense, to average NAV (as a percent) | 14.21% | 13.98% | 9.33% | 7.24% | 8.11% | 9.84% | 9.13% | 7.89% | 7.57% | 8.29% | ||||
| Ratio of operating expenses to average NAV (as a percent) | 14.03% | 13.37% | 9.06% | 6.92% | 7.89% | 9.84% | 8.97% | 7.79% | 7.51% | 8.26% | ||||
| Ratio of operating expenses, excluding interest expense, to average NAV (as a percent) | 7.73% | 7.43% | 5.07% | 4.49% | 4.80% | 5.58% | 5.10% | 4.88% | 4.69% | 5.46% | ||||
| Ratio of operating expenses, excluding interest expense and incentive fees, to average NAV (as a percent) | 0.0572 | 0.0538 | 0.0472 | 0.0439 | 0.0480 | 0.0495 | 0.0458 | 0.0461 | 0.0469 | 0.0493 | ||||
| Ratio of net investment income to average NAV (as a percent) | 7.73% | 8.05% | 7.90% | 8.26% | 7.67% | 8.11% | 8.25% | 8.28% | 8.48% | 7.98% | ||||
| ||||||||||||||