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Basis of Presentation and Significant Accounting Policies - Concentration of Risk (Details) $ in Millions |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Dec. 31, 2020 customer | Jun. 30, 2021 USD ($) customer | Jun. 30, 2020 customer | Jun. 30, 2021 USD ($) customer | Jun. 30, 2020 customer
Concentration of Risk |  |  |  |  |
Trade receivable, net | $ |  | $ 0.0 |  | $ 0.0 |
Customer Concentration Risk | Revenues |  |  |  |  |
Concentration of Risk |  |  |  |  |
Number of major partners |  | 2 | 1 | 2 | 2
Customer Concentration Risk | Revenues | Partner 1 |  |  |  |  |
Concentration of Risk |  |  |  |  |
Concentration risk (as a percent) |  | 55.00% | 88.00% | 57.00% | 56.00%
Customer Concentration Risk | Revenues | Partner 2 |  |  |  |  |
Concentration of Risk |  |  |  |  |
Concentration risk (as a percent) |  | 42.00% |  | 39.00% | 40.00%
Credit Concentration Risk | Trade Receivables | Partner 1 |  |  |  |  |
Concentration of Risk |  |  |  |  |
Number of major partners | 1 |  |  |  |
Concentration risk (as a percent) | 100.00% |  |  |  |

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