Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Total revenues	$ 652,112	$ 422,991	$ 322,176
Operating expenses:
Direct cost of services	58,824	34,754	40,625
Cost of goods sold	7,575	800	398
Selling, general and administrative expenses	385,219	310,508	227,884
Restructuring charge	1,699	8,506	12,374
Interest expense - Securities lending and loan participations sold	32,144	23,039	12,051
Total operating expenses	485,461	377,607	293,332
Operating income	166,651	45,384	28,844
Other income (expense):
Interest income	1,577	1,326	420
(Loss) income from equity investments	(1,431)	7,986	(437)
Interest expense	(50,205)	(33,393)	(8,382)
Income before income taxes	116,592	21,303	20,445
Provision for income taxes	(34,644)	(4,903)	(8,510)
Net income	81,948	16,400	11,935
Net income attributable to noncontrolling interests	337	891	379
Net income attributable to B. Riley Financial, Inc.	81,611	15,509	11,556
Preferred stock dividends	264
Net income available to common shareholders	$ 81,347	$ 15,509	$ 11,556
Basic income per common share	$ 3.08	$ 0.60	$ 0.50
Diluted income per common share	$ 2.95	$ 0.58	$ 0.48
Weighted average basic common shares outstanding	26,401,036	25,937,305	23,181,388
Weighted average diluted common shares outstanding	27,529,157	26,764,856	24,290,904
Services and fees [Member]
Revenues:
Total revenues	$ 566,956	$ 384,076	$ 302,113
Interest income - Loans and Securities lending [Member]
Revenues:
Total revenues	77,221	38,277	19,756
Sale of goods [Member]
Revenues:
Total revenues	$ 7,935	$ 638	$ 307