SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 19,761	$ 21,272	$ 45,461	$ 26,031	$ 19,842	$ 20,674	$ 14,947	$ 21,653	$ 112,525	$ 77,116	$ 76,132
Operating income (loss)	(1,326)	3,277	14,669	5,462	(3,864)	(1,253)	(1,056)	(1,258)	22,082	(7,431)	4,098
Income (loss) before income taxes	(1,418)	3,218	14,254	5,211	(3,993)	(1,303)	(1,501)	(1,884)	11,805	(5,801)	1,058
(Provision) benefit for income taxes	372	(600)	(5,685)	(1,775)	1,091	387	594	814	7,688	(2,886)	704
Net income (loss)	(1,046)	2,618	8,569	3,436	(2,902)	(916)	(907)	(1,070)	13,577	(5,795)	576
Net income (loss) attributable to B. Riley Financial, Inc.	$ (1,004)	$ 1,463	$ 8,664	$ 2,682	$ (2,822)	$ (868)	$ (777)	$ (1,334)	$ 11,805	$ (5,801)	$ 1,058
Earnings (loss) per share:
Basic	$ (0.06)	$ 0.09	$ 0.53	$ 0.17	$ (0.18)	$ (0.05)	$ (0.16)	$ (0.93)	$ 0.73	$ (0.60)	$ 0.74
Diluted	$ (0.06)	$ 0.09	$ 0.53	$ 0.17	$ (0.18)	$ (0.05)	$ (0.16)	$ (0.93)	$ 0.73	$ (0.60)	$ 0.71
Weighted average shares outstanding:
Basic	16,283,677	16,243,425	16,237,860	16,117,422	15,902,607	15,911,482	4,972,203	1,434,107	16,221,040	9,612,154	1,434,107
Diluted	16,283,677	16,344,649	16,310,829	16,162,304	15,902,607	15,911,482	4,972,203	1,434,107	16,265,915	9,612,154	1,495,328