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COMMITMENTS AND CONTINGENCIES, Business Combination Agreement (Q1) (Details) $ in Millions |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Sep. 14, 2020 | Mar. 31, 2021 USD ($) | Dec. 31, 2020
Business Combination Agreement [Abstract] |  |  |
Stock conversion basis at time of business combination | 1 | 1 | 1
Cash payment to option holders in lieu of assumption of a portion of vested options |  | $ 10 |

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- Definition The amount of cash payment to option holders in lieu of assumption of a portion of their vested options. + References No definition available. + Details
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- Definition Ratio applied to the conversion of stock, for example but not limited to, one share converted to two or two shares converted to one. + References No definition available. + Details
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