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Stockholders' Equity (DRSPP) (Details) - USD ($) | 3 Months Ended | 211 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2021 | Mar. 31, 2021 | Dec. 31, 2020 | Oct. 15, 2019
Class of Stock [Line Items] |  |  |  |
Common stock, shares authorized (in shares) | 874,300,000 | 874,300,000 | 874,300,000 |
DRSPP |  |  |  |
Class of Stock [Line Items] |  |  |  |
Common stock, shares authorized (in shares) |  |  |  | 9,000,000.0
Shares of common stock authorized and available for issuance (in shares) | 8,600,000 | 8,600,000 |  |
Common shares issued through DRSPP (in shares) | 105,272 | 34,719,675 |  |
Net proceeds from shares issued through DRSPP | $ 388,173 | $ 288,000,000.0 |  |

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