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Common Stock - Narrative (Details) - shares | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Common Stock [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Number of shares authorized to issue by regulatory authority | 3,900,000 |  | 3,900,000 |
Shares issued under sales agency agreements | 1,100,545 | 821,196 | 1,528,311 | 1,557,465
Sales Agency Agreement [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Shares issued under sales agency agreements | 1,100,000 |  | 1,400,000 |
Common stock shares authorized to issue | 2,500,000 |  | 2,500,000 |

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