Registration of securities issued in business combination transactions

COMMITMENTS AND CONTINGENCIES (Q3) (Details)

v3.21.4
COMMITMENTS AND CONTINGENCIES (Q3) (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Mar. 31, 2020
Sep. 30, 2021
Dec. 31, 2020
Loss Contingencies [Line Items]      
Purchase price $ 25,000   $ 25,000
Underwriting Agreement      
Loss Contingencies [Line Items]      
Deferred Fees, Payable per Unit   $ 0.35  
Deferred Fee Payable   $ 8,050,000  
Forward Purchase Agreement      
Loss Contingencies [Line Items]      
Purchase price   $ 100,000,000.0 $ 100,000,000.0
Commitment fee (in percent)   2.00% 2.00%
Open Market or Privately Negotiated Transactions      
Loss Contingencies [Line Items]      
Purchase price   $ 85,000,000.0 $ 85,000,000.0
Right Of First Refusal [Member]      
Loss Contingencies [Line Items]      
Percentage of outstanding common stock of the post-business combination   5.00% 5.00%
Maximum duration (in years)   3 years 3 years
Maximum      
Loss Contingencies [Line Items]      
Commitment carrying costs     $ 1,000,000.0
Maximum | Forward Purchase Agreement      
Loss Contingencies [Line Items]      
Commitment carrying costs   $ 1,000,000.0 100,000,000.0
Additional financing amount   $ 400,000,000 $ 400,000,000