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Common Stock - Narrative (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2020 shares | Jun. 30, 2020 Agreement | Sep. 30, 2019 shares | Sep. 30, 2020 shares | Sep. 30, 2019 shares | Dec. 31, 2019 shares
Class Of Stock [Line Items] |  |  |  |  |  |
Common stock, shares authorized | 200,000,000 |  |  | 200,000,000 |  | 200,000,000
Common Stock [Member] |  |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |  |
Shares issued under sales agency agreements | 821,196 |  | 597,672 | 1,557,465 | 1,020,633 |
Sales Agency Agreement |  |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |  |
Number of agreement | Agreement |  | 4 |  |  |  |
Common stock, shares authorized | 3,200,000 |  |  | 3,200,000 |  |
Common stock shares authorized under sales agency agreements remaining shares authorized to sell | 1,800,000 |  |  | 1,800,000 |  |
Sales Agency Agreement | Common Stock [Member] |  |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |  |
Shares issued under sales agency agreements | 800,000 |  |  | 1,400,000 |  |

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