RESTATEMENT OF PREVIOUSLY ISSUED FINANCIAL STATEMENTS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenues:
Services and fees	$ 235,559	$ 202,814
Trading (loss) income and fair value adjustments on loans		(19,278)
Interest income - Loans and securities lending	77,186	61,426
Sale of goods		1,878
Total revenues	432,090	246,840
Operating expenses:
Direct cost of services	54,397	11,651
Cost of goods sold		2,251
Selling, general and administrative expenses	212,627	175,199
Interest expense - Securities lending and loan participations sold	32,424	11,766
Total operating expenses	347,167	200,867
Operating income	84,923	45,973
Other income (expense):
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
Income from equity method 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)
Basic (loss) income per common share (in dollars per share)	$ 0.53	$ (0.43)
Diluted (loss) income per common share (in dollars per share)	$ 0.51	$ (0.43)
Weighted average basic common shares outstanding (in shares)	28,585,337	27,855,033
Weighted average diluted common shares outstanding (in shares)	29,513,435	27,855,033
As Previously Reported | Dividend Income and Investment Gain (Loss) Classification Error
Revenues:
Services and fees		$ 210,675
Trading (loss) income and fair value adjustments on loans		(68,390)
Interest income - Loans and securities lending		61,426
Sale of goods		1,878
Total revenues		205,589
Operating expenses:
Direct cost of services		11,651
Cost of goods sold		2,251
Selling, general and administrative expenses		175,199
Interest expense - Securities lending and loan participations sold		11,766
Total operating expenses		200,867
Operating income		4,722
Other income (expense):
Interest income		67
Dividend income		0
Realized and unrealized gains (losses) on investments		0
Change in fair value of financial instruments and other		5,981
Income from equity method investments		6,775
Interest expense		(30,436)
Income (loss) before income taxes		(12,891)
(Provision for) benefit from income taxes		3,695
Net income (loss)		(9,196)
Net (loss) income attributable to noncontrolling interests and redeemable noncontrolling interests		866
Net income (loss) attributable to B. Riley Financial, Inc.		(10,062)
Preferred stock dividends		2,002
Net income (loss) available to common shareholders		(12,064)
Net income (loss) available to common shareholders		$ (12,064)
Basic (loss) income per common share (in dollars per share)		$ (0.43)
Diluted (loss) income per common share (in dollars per share)		$ (0.43)
Weighted average basic common shares outstanding (in shares)		27,855,033
Weighted average diluted common shares outstanding (in shares)		27,855,033
Restatement Adjustments | Dividend Income and Investment Gain (Loss) Classification Error
Revenues:
Services and fees		$ (7,861)
Trading (loss) income and fair value adjustments on loans		49,112
Interest income - Loans and securities lending		0
Sale of goods		0
Total revenues		41,251
Operating expenses:
Direct cost of services		0
Cost of goods sold		0
Selling, general and administrative expenses		0
Interest expense - Securities lending and loan participations sold		0
Total operating expenses		0
Operating income		41,251
Other income (expense):
Interest income		0
Dividend income		7,861
Realized and unrealized gains (losses) on investments		(49,112)
Change in fair value of financial instruments and other		0
Income from equity method investments		0
Interest expense		0
Income (loss) before income taxes		0
(Provision for) benefit from income taxes		0
Net income (loss)		0
Net (loss) income attributable to noncontrolling interests and redeemable noncontrolling interests		0
Net income (loss) attributable to B. Riley Financial, Inc.		0
Preferred stock dividends		0
Net income (loss) available to common shareholders		0
Net income (loss) available to common shareholders		$ 0