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Selected Financial Ratios and Other Data - Summary of Selected Financial Ratios and Other Data (Detail) - USD ($) $ / shares in Units, $ in Thousands | 3 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2018 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Net share data |  |  |  |  |  |
Net asset value at the beginning of the year |  | $ 11.80 |  |  |  |
Net investment income (loss) |  | (0.15) |  |  |  |
Income tax provision (benefit) |  | 0.03 |  |  |  |
Net realized gains (losses) on investments |  | (1.44) |  |  |  |
Net change in unrealized appreciation on investments |  | 0.94 |  |  |  |
Net increase (decrease) in net assets resulting from operations |  | (0.62) |  |  |  |
Issuance of common stock |  | (0.03) |  |  |  |
Total increase (decrease) in net asset value |  | (0.65) |  |  |  |
Net asset value at the end of the period/year | [1] | 11.15 |  |  |  |
Per share market value at beginning of year |  | 3.53 |  |  |  |
Per share market value at end of period/year |  | $ 4.65 |  |  |  |
Total return | [2] | (129.00%) |  |  |  |
Ratios/supplemental data |  |  |  |  |  |
Total shareholders’ equity (net assets) |  | $ 272,437 | $ 304,561 | $ 334,468 | $ 290,204 | $ 287,159
Average net assets |  | $ 284,021 |  |  |  |
Total expense ratio | [3],[4] | 10.02% |  |  |  |
Operating expenses to average net assets | [3] | 5.87% |  |  |  |
Net investment income (loss) after income taxes to average net assets | [3] | (4.61%) |  |  |  |
[1] | Includes $0.00 of undistributed net investment income per share as of March 31, 2018 and $0.00 of undistributed net realized gains per share for the period presented.
[2] | Total return is calculated by dividing the change in market value of a share of common stock during the year, assuming the reinvestment of distributions on the payment date, by the per share market value at the beginning of the year.
[3] | MSC has assumed certain of the Company’s servicing obligations, and as a result, servicing fee income of $1,290, and operating expenses of $1,150, which formerly were the Company’s, were now MSC’s for the three months ended March 31, 2018. Excluding the impact of the MSC amounts, the total expense ratio, operating expense ratio, and net investment income (loss) ratio would have been 11.75%, 6.88%, and 7.51% in the March 31, 2018 quarter.
[4] | Total expense ratio represents total expenses (interest expense, operating expenses, and income taxes) divided by average net assets.

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