EARNINGS PER SHARE - Schedule of basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
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)
Weighted average common shares outstanding:
Basic (in shares)	28,585,337	27,855,033
Effect of dilutive potential common shares:
Restricted stock units and warrants (in shares)	928,098	0
Diluted (in shares)	29,513,435	27,855,033
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)