STOCKHOLDERS' EQUITY - Stock options (Details) - Common Class D - Employee Stock Option [Member] - 2019 Equity and Performance Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
STOCKHOLDERS' EQUITY
Number of Options, Outstanding at Beginning of Year	5,224,136
Number of Options, Grants	740,139
Number of Options, Exercised	0
Number of Option, Forfeited/cancelled/expired/settled	0
Number of Options, Balance at End of Year	5,964,275	5,224,136
Number of Options, Vested and expected to vest	5,909,679
Number of Options, Unvested	468,035
Number of Options, Exercisable	5,496,240
Weighted-Average Exercise Price, Outstanding at Beginning of Year (in dollars per share)	$ 2.90
Weighted-Average Exercise Price, Grants (in dollars per share)	3.56
Weighted-Average Exercise Price, Exercised (in dollars per share)	0
Weighted-Average Exercise Price, Forfeited/cancelled/expired/settled (in dollars per share)	0
Weighted-Average Exercise Price, Balance at End of Year (in dollars per share)	2.99	$ 2.90
Weighted-Average Exercise Price, Vested and expected to vest (in dollars per share)	2.97
Weighted-Average Exercise Price, Unvested (in dollars per share)	4.61
Weighted-Average Exercise Price, Exercisable (in dollars per share)	$ 2.85
Weighted-Average Remaining Contractual Term, Outstanding (in years)	5 years 7 months 13 days	5 years 3 months 10 days
Weighted-Average Remaining Contractual Term, Grants (in years)	0 years
Weighted-Average Remaining Contractual Term, Exercised (in years)	0 years
Weighted-Average Remaining Contractual Term, Forfeited/cancelled/expired/settled (in years)	0 years
Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	5 years 7 months 2 days
Weighted-Average Remaining Contractual Term, Unvested (in years)	8 years 11 months 23 days
Weighted-Average Remaining Contractual Term, Exercisable (in years)	5 years 3 months 29 days
Aggregate Intrinsic Value, Outstanding	$ 377,161	$ 5,021,952
Aggregate Intrinsic Value, Grants	0
Aggregate Intrinsic Value, Exercised	0
Aggregate Intrinsic Value, Forfeited/cancelled/expired/settled	0
Aggregate Intrinsic Value, Vested and expected to vest	377,161
Aggregate Intrinsic Value, Unvested	0
Aggregate Intrinsic Value, Exercisable	$ 377,161