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Fair Value Measurements - Schedule of change in the derivative liability forward purchase agreement (Q3) (Details) - USD ($) |  | 3 Months Ended
--- | --- | ---
Mar. 31, 2021 | Sep. 30, 2021 | Jun. 30, 2021
Fair Value Disclosures [Abstract] |  |  |
Derivative liability opening balance | $ 11,655,000 | $ 12,321,000 | $ 11,655,000
Change in fair value of derivative liability - forward purchase agreement |  | (3,330,000) | 666,000
Derivative liability ending balance | $ 11,655,000 | $ 8,991,000 | $ 12,321,000

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- Definition Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958 + Details
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Balance Type: | debit
Period Type: | instant

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- References No definition available. + Details
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- Definition Amount of Change in fair value of derivative liability forward purchase agreement. + References No definition available. + Details
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