Financial Highlights - Schedule of Financial Highlights of the Company (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||||||||||||||||
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Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
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Net investment income before gains and losses per common share: | |||||||||||||||||
Investment Company, Issuance of Shares, Per Share | [1] | $ 0.34 | $ (0.08) | $ 0.01 | $ 0.20 | $ 0.23 | |||||||||||
Net asset value at beginning of period | [1] | 11.22 | 11.26 | 10.55 | 9.90 | 9.96 | |||||||||||
Net investment income | [1] | 1.50 | 1.29 | 1.39 | 1.41 | 1.20 | |||||||||||
Total from investment operations | [1] | 0.81 | 1.50 | 2.02 | 1.71 | 0.85 | |||||||||||
Net increase (decrease) in net assets from capital share transactions | [1] | 0.34 | (0.08) | 0.01 | 0.20 | 0.23 | |||||||||||
Distributions of net investment income | 1.97 | 1.55 | 1.38 | ||||||||||||||
Stock-based compensation expense included in net investment income and other movements | [1],[2] | 0.15 | 0.09 | 0.07 | 0.07 | 0.12 | |||||||||||
Net asset value at end of period | [1] | 10.53 | 11.22 | 11.26 | 10.55 | 9.90 | |||||||||||
Ratios and supplemental data (in thousands, except per share data): | |||||||||||||||||
Per share market value at end of period | $ 13.22 | $ 16.59 | $ 14.42 | $ 14.02 | $ 11.05 | ||||||||||||
Total return | [3] | (10.14%) | 25.62% | 14.31% | 39.36% | (7.56%) | |||||||||||
Shares outstanding at end of period | 133,045,000 | 116,619,000 | 114,726,000 | 107,364,000 | 96,501,000 | ||||||||||||
Basic | 125,189,000 | 114,742,000 | 111,985,000 | 101,132,000 | 90,929,000 | ||||||||||||
Diluted | 126,659,000 | 115,955,000 | 112,267,000 | ||||||||||||||
Net assets at end of period | $ (1,401,459) | $ (1,308,547) | $ (1,291,704) | $ (1,133,049) | $ (955,444) | ||||||||||||
Ratio of total expense to average net assets | [4] | 9.92% | 9.86% | 11.30% | 11.95% | 10.73% | |||||||||||
Ratio of net investment income before investment gains and losses to average net assets | [4] | 13.96% | 11.28% | 13.64% | 13.74% | 11.78% | |||||||||||
Portfolio turnover rate | [5] | 19.29% | 51.58% | 32.38% | 31.30% | 38.76% | |||||||||||
Weighted average debt outstanding | $ 1,468,335 | $ 1,248,177 | $ 1,309,903 | $ 1,177,379 | $ 826,931 | ||||||||||||
Weighted average debt per common share | $ 11.73 | $ 10.88 | $ 11.70 | $ 11.64 | $ 9.09 | ||||||||||||
Ordinary Income [Member] | |||||||||||||||||
Net investment income before gains and losses per common share: | |||||||||||||||||
Distributions of net investment income | [1],[6] | 1.63 | 1.06 | 1.03 | 1.15 | 1.26 | |||||||||||
Capital Gains Member | |||||||||||||||||
Net investment income before gains and losses per common share: | |||||||||||||||||
Distributions of net investment income | [1],[6] | 0.36 | 0.49 | 0.36 | 0.18 | 0 | |||||||||||
Realized Gain Loss [Member] | |||||||||||||||||
Net investment income before gains and losses per common share: | |||||||||||||||||
Net realized gain (loss) | [1] | (0.01) | 0.18 | (0.50) | 0.16 | (0.12) | |||||||||||
Unrealized Gain Loss Member | |||||||||||||||||
Net investment income before gains and losses per common share: | |||||||||||||||||
Net realized gain (loss) | [1] | $ (0.68) | $ 0.03 | $ 1.13 | $ 0.14 | $ (0.23) | |||||||||||
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