FAIR VALUE MEASUREMENTS, Level 3 Fair Value Measurement Inputs (Details)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurements [Abstract]
Expected life of the options to convert	5 years
Private Placement Warrant [Member]
Fair Value Measurements [Abstract]
Expected life of the options to convert	5 years 6 months 29 days	5 years 11 months 12 days
Private Placement Warrant [Member] | Common Stock Price [Member]
Fair Value Measurements [Abstract]
Measurement input	10.13	9.77
Private Placement Warrant [Member] | Volatility [Member]
Fair Value Measurements [Abstract]
Measurement input	0.1050	0.2259
Private Placement Warrant [Member] | Risk-Free Rate [Member]
Fair Value Measurements [Abstract]
Measurement input	0.0108	0.0050
Private Placement Warrant [Member] | Dividend Yield [Member]
Fair Value Measurements [Abstract]
Measurement input	0	0
FPA liability - Committed [Member]
Fair Value Measurements [Abstract]
Expected life of the options to convert	6 months 29 days	11 months 12 days
FPA liability - Committed [Member] | Common Stock Price [Member]
Fair Value Measurements [Abstract]
Measurement input	10.13	9.77
FPA liability - Committed [Member] | Risk-Free Rate [Member]
Fair Value Measurements [Abstract]
Measurement input	0.0006	0.0010
FPA liability - Optional [Member]
Fair Value Measurements [Abstract]
Expected life of the options to convert	6 months 29 days	11 months 12 days
FPA liability - Optional [Member] | Common Stock Price [Member]
Fair Value Measurements [Abstract]
Measurement input	10.13	9.77
FPA liability - Optional [Member] | Volatility [Member]
Fair Value Measurements [Abstract]
Measurement input	0.10	0.10
FPA liability - Optional [Member] | Risk-Free Rate [Member]
Fair Value Measurements [Abstract]
Measurement input	0.0006	0.0010