REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of revenues from contracts with customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	$ 293,134	$ 199,701
Interest income - Loans and securities lending	77,186	61,426
Trading (loss) gain on investments	8,292	(30,216)
Fair value adjustment on loans	43,276	10,938
Other	10,202	4,991
Total revenues	432,090	246,840
Capital Markets Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	49,031	56,118
Interest income - Loans and securities lending	77,186	61,426
Trading (loss) gain on investments	7,020	(30,738)
Fair value adjustment on loans	43,276	10,938
Other	8,898	5,105
Total revenues	185,411	102,849
Wealth Management Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	47,238	77,071
Interest income - Loans and securities lending	0	0
Trading (loss) gain on investments	1,272	522
Fair value adjustment on loans	0	0
Other	1,304	(114)
Total revenues	49,814	77,479
Auction and Liquidation Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	5,660	3,355
Interest income - Loans and securities lending	0	0
Trading (loss) gain on investments	0	0
Fair value adjustment on loans	0	0
Other	0	0
Total revenues	5,660	3,355
Financial Consulting Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	25,010	25,936
Interest income - Loans and securities lending	0	0
Trading (loss) gain on investments	0	0
Fair value adjustment on loans	0	0
Other	0
Total revenues	25,010	25,936
Communications Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	86,919	31,965
Interest income - Loans and securities lending	0	0
Trading (loss) gain on investments	0	0
Fair value adjustment on loans	0	0
Other	0	0
Total revenues	86,919	31,965
Consumer Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	70,003	4,557
Interest income - Loans and securities lending	0	0
Trading (loss) gain on investments	0	0
Fair value adjustment on loans	0	0
Other	0	0
Total revenues	70,003	4,557
Other Segments
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	9,273	699
Total revenues	9,273	699
Corporate finance, consulting and investment banking fees
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	53,664	58,643
Corporate finance, consulting and investment banking fees | Capital Markets Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	39,149	41,673
Corporate finance, consulting and investment banking fees | Wealth Management Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Corporate finance, consulting and investment banking fees | Auction and Liquidation Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Corporate finance, consulting and investment banking fees | Financial Consulting Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	14,515	16,970
Corporate finance, consulting and investment banking fees | Communications Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Corporate finance, consulting and investment banking fees | Consumer Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Corporate finance, consulting and investment banking fees | Other Segments
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Wealth and asset management fees
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	43,974	66,622
Wealth and asset management fees | Capital Markets Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	664	2,400
Wealth and asset management fees | Wealth Management Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	43,310	64,222
Wealth and asset management fees | Auction and Liquidation Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Wealth and asset management fees | Financial Consulting Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Wealth and asset management fees | Communications Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Wealth and asset management fees | Consumer Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Wealth and asset management fees | Other Segments
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Commissions, fees and reimbursed expenses
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	29,085	37,215
Commissions, fees and reimbursed expenses | Capital Markets Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	9,218	12,045
Commissions, fees and reimbursed expenses | Wealth Management Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	3,928	12,849
Commissions, fees and reimbursed expenses | Auction and Liquidation Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	5,444	3,355
Commissions, fees and reimbursed expenses | Financial Consulting Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	10,495	8,966
Commissions, fees and reimbursed expenses | Communications Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Commissions, fees and reimbursed expenses | Consumer Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Commissions, fees and reimbursed expenses | Other Segments
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Subscription services
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	83,008	27,813
Subscription services | Capital Markets Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Subscription services | Wealth Management Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Subscription services | Auction and Liquidation Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Subscription services | Financial Consulting Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Subscription services | Communications Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	83,008	27,813
Subscription services | Consumer Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Subscription services | Other Segments
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Sale of goods
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	67,777	1,878
Sale of goods | Capital Markets Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Sale of goods | Wealth Management Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Sale of goods | Auction and Liquidation Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	216	0
Sale of goods | Financial Consulting Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Sale of goods | Communications Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	1,867	1,878
Sale of goods | Consumer Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	65,694	0
Advertising, licensing and other
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	15,626	7,530
Advertising, licensing and other | Capital Markets Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Advertising, licensing and other | Wealth Management Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Advertising, licensing and other | Auction and Liquidation Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Advertising, licensing and other | Financial Consulting Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Advertising, licensing and other | Communications Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	2,044	2,274
Advertising, licensing and other | Consumer Segment
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	4,309	4,557
Advertising, licensing and other | Other Segments
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	9,273	699
Product | Other Segments
Revenue from External Customer [Line Items]
Total revenues from contracts with customers	0	0
Interest Income Loans And Securities Lending | Other Segments
Revenue from External Customer [Line Items]
Interest income - Loans and securities lending	0	0
Trading Gains losses On Investments | Other Segments
Revenue from External Customer [Line Items]
Trading (loss) gain on investments	0	0
Fair Value Adjustment On Loans | Other Segments
Revenue from External Customer [Line Items]
Fair value adjustment on loans	0	0
Other | Other Segments
Revenue from External Customer [Line Items]
Other	$ 0	$ 0