Consolidated Statements of Operations - USD ($)	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Services and fees	$ 243,837,000	$ 257,310,000	$ 191,662,000	$ 202,814,000	$ 308,062,000	$ 295,561,000	$ 262,607,000	$ 286,995,000	$ 394,476,000	$ 549,602,000	$ 651,786,000	$ 845,163,000	$ 895,623,000	$ 1,153,225,000	$ 645,906,000
Trading (loss) income and fair value adjustments on loans	(58,670,000)	(6,917,000)	(117,763,000)	(19,278,000)	54,848,000	34,892,000	18,411,000	112,394,000	(137,041,000)	130,805,000	(143,958,000)	165,697,000	(202,628,000)	220,545,000	56,677,000
Interest income - Loans and securities lending	62,545,000	57,594,000	63,835,000	61,426,000	33,443,000	26,869,000	25,491,000	36,920,000	125,261,000	62,411,000	182,855,000	89,280,000	245,400,000	122,723,000	102,499,000
Revenues - Sale of goods	134,380,000	4,130,000	1,887,000	1,878,000	3,961,000	34,959,000	12,457,000	6,828,000	3,765,000	19,285,000	7,895,000	54,244,000	142,275,000	58,205,000	29,135,000
Total revenues	382,092,000	312,117,000	139,621,000	246,840,000	400,314,000	392,281,000	318,966,000	443,137,000	386,461,000	762,103,000	698,578,000	1,154,384,000	1,080,670,000	1,554,698,000	834,217,000
Operating expenses:
Direct cost of services	68,496,000	44,523,000	17,785,000	11,651,000	12,955,000	18,019,000	12,094,000	11,322,000	29,436,000	23,416,000	73,959,000	41,435,000	142,455,000	54,390,000	60,451,000
Cost of goods sold	71,313,000	3,089,000	1,994,000	2,251,000	5,559,000	12,442,000	3,626,000	5,326,000	4,245,000	8,952,000	7,334,000	21,394,000	78,647,000	26,953,000	12,460,000
Selling, general and administrative expenses	208,552,000	163,727,000	167,136,000	175,199,000	270,712,000	244,218,000	199,922,000	191,344,000	342,335,000	391,266,000	506,062,000	635,484,000	714,614,000	906,196,000	428,537,000
Restructuring charge	995,000	8,016,000	0	0					0		8,016,000		9,011,000	0	1,557,000
Impairment of tradenames													0	0	12,500,000
Interest expense - Securities lending and loan participations sold	22,738,000	17,447,000	14,544,000	11,766,000	12,362,000	10,097,000	10,983,000	19,189,000	26,310,000	30,172,000	43,757,000	40,269,000	66,495,000	52,631,000	42,451,000
Total operating expenses	372,094,000	236,802,000	201,459,000	200,867,000	301,588,000	284,776,000	226,625,000	227,181,000	402,326,000	453,806,000	639,128,000	738,582,000	1,011,222,000	1,040,170,000	557,956,000
Operating income	9,998,000	75,315,000	(61,838,000)	45,973,000	98,726,000	107,505,000	92,341,000	215,956,000	(15,865,000)	308,297,000	59,450,000	415,802,000	69,448,000	514,528,000	276,261,000
Other income (expense):
Interest income	1,482,000	686,000	500,000	67,000	54,000	70,000	56,000	49,000	567,000	105,000	1,253,000	175,000	2,735,000	229,000	564,000
Dividend income	9,595,000	9,175,000	9,243,000	7,861,000	7,786,000	5,936,000	3,536,000	2,474,000	17,104,000	6,010,000	26,279,000	11,946,000	35,874,000	19,732,000	21,163,000
Gain on equity method investment	(64,874,000)	19,071,000	(106,164,000)	(49,112,000)	14,010,000	(16,695,000)	14,268,000	154,548,000	(155,276,000)	168,816,000	(136,205,000)	152,121,000	(201,079,000)	166,131,000	47,341,000
Change in fair value of financial instruments and other	460,000	(574,000)	4,321,000	5,981,000	(4,471,000)	1,758,000	6,509,000	0	10,302,000	6,509,000	9,728,000	8,267,000	10,188,000	3,796,000	0
Income (loss) from equity method investments	285,000	(91,000)	(3,399,000)	6,775,000	1,629,000	1,149,000	(852,000)	875,000	3,376,000	23,000	3,285,000	1,172,000	3,570,000	2,801,000	(623,000)
Interest expense	(44,399,000)	(34,587,000)	(31,764,000)	(30,436,000)	(26,441,000)	(25,372,000)	(20,856,000)	(19,786,000)	(62,200,000)	(40,642,000)	(96,787,000)	(66,014,000)	(141,186,000)	(92,455,000)	(65,249,000)
(Loss) income before income taxes	(87,453,000)	68,995,000	(189,101,000)	(12,891,000)	91,293,000	74,351,000	95,002,000	354,116,000	(201,992,000)	449,118,000	(132,997,000)	523,469,000	(220,450,000)	614,762,000	279,457,000
Benefit from (provision for) income taxes	23,998,000	(16,350,000)	52,513,000	3,695,000	(23,847,000)	(22,693,000)	(19,902,000)	(97,518,000)	56,208,000	(117,420,000)	39,858,000	(140,113,000)	63,856,000	(163,960,000)	(75,440,000)
Net (loss) income	(63,455,000)	52,645,000	(136,588,000)	(9,196,000)	67,446,000	51,658,000	75,100,000	256,598,000	(145,784,000)	331,698,000	(93,139,000)	383,356,000	(156,594,000)	450,802,000	204,017,000
Net income (loss) attributable to noncontrolling interests and redeemable noncontrolling interests	(6,010,000)	4,808,000	3,571,000	866,000	3,274,000	1,108,000	(576,000)	1,942,000	4,437,000	1,366,000	9,245,000	2,474,000	3,235,000	5,748,000	(1,131,000)
Net (loss) income attributable to B. Riley Financial, Inc.	(57,445,000)	47,837,000	(140,159,000)	(10,062,000)	64,172,000	50,550,000	75,676,000	254,656,000	(150,221,000)	330,332,000	(102,384,000)	380,882,000	(159,829,000)	445,054,000	205,148,000
Preferred stock dividends	2,002,000	2,002,000	2,002,000	2,002,000	1,990,000	1,929,000	1,789,000	1,749,000	4,004,000	3,538,000	6,006,000	5,467,000	8,008,000	7,457,000	4,710,000
Net (loss) income available to common shareholders	(59,447,000)	45,835,000	(142,161,000)	(12,064,000)	62,182,000	48,621,000	73,887,000	252,907,000	(154,225,000)	326,794,000	(108,390,000)	375,415,000	(167,837,000)	437,597,000	200,438,000
Net (loss) income available to common shareholders	$ (59,447,000)	$ 45,835,000	$ (142,161,000)	$ (12,064,000)	$ 62,182,000	$ 48,621,000	$ 73,887,000	$ 252,907,000	$ (154,225,000)	$ 326,794,000	$ (108,390,000)	$ 375,415,000	$ (167,837,000)	$ 437,597,000	$ 200,438,000
Basic income per common share (in dollars per share)	$ (2.08)	$ 1.62	$ (5.07)	$ (0.43)	$ 2.26	$ 1.76	$ 2.70	$ 9.38	$ (5.52)	$ 12.03	$ (3.86)	$ 13.75	$ (5.95)	$ 15.99	$ 7.83
Diluted income per common share (in dollars per share)	$ (2.08)	$ 1.53	$ (5.07)	$ (0.43)	$ 2.08	$ 1.69	$ 2.58	$ 8.81	$ (5.52)	$ 11.39	$ (3.86)	$ 13.07	$ (5.95)	$ 15.09	$ 7.56
Weighted average basic common shares outstanding (in shares)	28,545,714	28,293,064	28,051,570	27,855,033	27,569,188	27,570,716	27,344,184	26,972,275	27,953,845	27,159,257	28,068,160	27,297,917	28,188,530	27,366,292	25,607,278
Weighted average diluted common shares outstanding (in shares)	28,545,714	29,968,417	28,051,570	27,855,033	29,840,704	28,794,066	28,668,465	28,710,368	27,953,845	28,690,444	28,068,160	28,726,492	28,188,530	29,005,602	26,508,397