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Summary of Significant Accounting Policies (Equity-Based Compensation, Taxes, Derivatives) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Vesting period | 3 years |
Percentage of annual REIT taxable income intended to be distributed to stockholders | 100.00% |
REIT income tax expense | $ 0 |
Deferred income tax expense (benefit) | 0 | $ 0
Valuation allowance decrease | $ 74,100,000 |

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