BUSINESS SEGMENTS - Schedule of reportable segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Services and fees	$ 235,559	$ 202,814
Trading income (loss) and fair value adjustments on loans	51,568	(19,278)
Interest income - Loans and securities lending	77,186	61,426
Sale of goods	67,777	1,878
Revenues	432,090	246,840
Direct cost of services	(54,397)	(11,651)
Cost of goods sold	(47,626)	(2,251)
Selling, general and administrative expenses	(212,627)	(175,199)
Interest expense - Securities lending and loan participations sold	(32,424)	(11,766)
Depreciation and amortization	(13,077)	(7,848)
Restructuring charge	(93)	0
Operating income	84,923	45,973
Interest income	2,574	67
Dividend income	13,204	7,861
Realized and unrealized gains (losses) on investments	(28,442)	(49,112)
Change in fair value of financial instruments and other	(209)	5,981
(Loss) income from equity investments	(10)	6,775
Interest expense	(47,561)	(30,436)
Income (loss) before income taxes	24,479	(12,891)
(Provision for) benefit from income taxes	(7,919)	3,695
Net income (loss)	16,560	(9,196)
Net (loss) income attributable to noncontrolling interests and redeemable noncontrolling interests	(595)	866
Net income (loss) attributable to B. Riley Financial, Inc.	17,155	(10,062)
Preferred stock dividends	2,012	2,002
Net income (loss) available to common shareholders	15,143	(12,064)
Net income (loss) available to common shareholders	15,143	(12,064)
Operating Segments
Segment Reporting Information [Line Items]
Operating income	103,805	61,276
Corporate And Reconciling Items
Segment Reporting Information [Line Items]
Services and fees	9,273	699
Direct cost of services	(6,536)	0
Corporate and other expenses	(21,619)	(16,002)
Capital Markets Segment
Segment Reporting Information [Line Items]
Interest income - Loans and securities lending	77,186	61,426
Revenues	185,411	102,849
Capital Markets Segment | Operating Segments
Segment Reporting Information [Line Items]
Services and fees	57,929	61,223
Trading income (loss) and fair value adjustments on loans	50,296	(19,800)
Interest income - Loans and securities lending	77,186	61,426
Revenues	185,411	102,849
Selling, general and administrative expenses	(65,711)	(34,117)
Interest expense - Securities lending and loan participations sold	(32,424)	(11,766)
Depreciation and amortization	(1,256)	(1,893)
Operating income	86,020	55,073
Wealth Management Segment
Segment Reporting Information [Line Items]
Interest income - Loans and securities lending	0	0
Revenues	49,814	77,479
Wealth Management Segment | Operating Segments
Segment Reporting Information [Line Items]
Services and fees	48,542	76,957
Trading income (loss) and fair value adjustments on loans	1,272	522
Revenues	49,814	77,479
Selling, general and administrative expenses	(47,322)	(85,742)
Depreciation and amortization	(1,086)	(1,833)
Restructuring charge	(33)	0
Operating income	1,373	(10,096)
Auction and Liquidation Segment
Segment Reporting Information [Line Items]
Interest income - Loans and securities lending	0	0
Revenues	5,660	3,355
Auction and Liquidation Segment | Operating Segments
Segment Reporting Information [Line Items]
Services and fees	5,444	3,355
Sale of goods	216	0
Revenues	5,660	3,355
Direct cost of services	(3,128)	(2,335)
Cost of goods sold	(52)	0
Selling, general and administrative expenses	(2,280)	(1,820)
Operating income	200	(800)
Financial Consulting Segment
Segment Reporting Information [Line Items]
Interest income - Loans and securities lending	0	0
Revenues	25,010	25,936
Financial Consulting Segment | Operating Segments
Segment Reporting Information [Line Items]
Services and fees	25,010	25,936
Selling, general and administrative expenses	(21,149)	(20,943)
Depreciation and amortization	(78)	(81)
Operating income	3,783	4,912
Communications Segment
Segment Reporting Information [Line Items]
Interest income - Loans and securities lending	0	0
Revenues	86,919	31,965
Communications Segment | Operating Segments
Segment Reporting Information [Line Items]
Services and fees	85,052	30,087
Sale of goods	1,867	1,878
Revenues	86,919	31,965
Direct cost of services	(44,733)	(9,316)
Cost of goods sold	(2,168)	(2,251)
Selling, general and administrative expenses	(22,544)	(8,245)
Depreciation and amortization	(6,631)	(3,184)
Restructuring charge	(60)	0
Operating income	10,783	8,969
Consumer Segment
Segment Reporting Information [Line Items]
Interest income - Loans and securities lending	0	0
Revenues	70,003	4,557
Consumer Segment | Operating Segments
Segment Reporting Information [Line Items]
Services and fees	4,309	4,557
Sale of goods	65,694	0
Revenues	70,003	4,557
Cost of goods sold	(45,406)	0
Selling, general and administrative expenses	(20,112)	(756)
Depreciation and amortization	(2,839)	(583)
Operating income	$ 1,646	$ 3,218