RESTATEMENT OF PREVIOUSLY ISSUED FINANCIAL STATEMENTS (Details) - 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
As Previously Reported | Dividend Income and Investment Gain (Loss) Classification Error
Revenues:
Services and fees		$ 266,485,000	$ 200,905,000	$ 210,675,000	$ 315,848,000	$ 301,497,000	$ 266,143,000	$ 289,469,000	$ 411,580,000	$ 555,612,000	$ 678,065,000	$ 857,109,000		$ 1,172,957,000	$ 667,069,000
Trading (loss) income and fair value adjustments on loans		12,154,000	(223,927,000)	(68,390,000)	68,858,000	18,197,000	32,679,000	266,942,000	(292,317,000)	299,621,000	(280,163,000)	317,818,000		386,676,000	104,018,000
Interest income - Loans and securities lending		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		122,723,000	102,499,000
Revenues - Sale of goods		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		58,205,000	29,135,000
Total revenues		340,363,000	42,700,000	205,589,000	422,110,000	381,522,000	336,770,000	600,159,000	248,289,000	936,929,000	588,652,000	1,318,451,000		1,740,561,000	902,721,000
Operating expenses:
Direct cost of services		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		54,390,000	60,451,000
Cost of goods sold		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		26,953,000	12,460,000
Selling, general and administrative expenses		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		906,196,000	428,537,000
Restructuring charge		8,016,000									8,016,000				1,557,000
Impairment of tradenames															12,500,000
Interest expense - Securities lending and loan participations sold		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		52,631,000	42,451,000
Total operating expenses		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		1,040,170,000	557,956,000
Operating income		103,561,000	(158,759,000)	4,722,000	120,522,000	96,746,000	110,145,000	372,978,000	(154,037,000)	483,123,000	(50,476,000)	579,869,000		700,391,000	344,765,000
Other income (expense):
Interest income		686,000	500,000	67,000	54,000	70,000	56,000	49,000	567,000	105,000	1,253,000	175,000		229,000	564,000
Dividend income		0	0	0	0	0	0	0	0	0	0	0		0	0
Gain on equity method investment		0	0	0	0	0	0	0	0	0	0	0		0	0
Change in fair value of financial instruments and other		(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		3,796,000
Income (loss) from equity method investments		(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		2,801,000	(623,000)
Interest expense		(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)		(92,455,000)	(65,249,000)
(Loss) income before income taxes		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		614,762,000	279,457,000
Benefit from (provision for) income taxes		(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)		(163,960,000)	(75,440,000)
Net (loss) income		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		450,802,000	204,017,000
Net income (loss) attributable to noncontrolling interests and redeemable noncontrolling interests		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		5,748,000	(1,131,000)
Net (loss) income attributable to B. Riley Financial, Inc.		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		445,054,000	205,148,000
Preferred stock dividends		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		7,457,000	4,710,000
Net (loss) income available to common shareholders		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		437,597,000	200,438,000
Net (loss) income available to common shareholders		$ 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		$ 437,597,000	$ 200,438,000
Basic income per common share (in dollars per share)		$ 1.62	$ (5.07)	$ (0.43)	$ 2.26	$ 1.76	$ 2.70	$ 9.38	$ (5.52)	$ 12.03	$ (3.86)	$ 13.75		$ 15.99	$ 7.83
Diluted income per common share (in dollars per share)		$ 1.53	$ (5.07)	$ (0.43)	$ 2.08	$ 1.69	$ 2.58	$ 8.81	$ (5.52)	$ 11.39	$ (3.86)	$ 13.07		$ 15.09	$ 7.56
Weighted average basic common shares outstanding (in shares)		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		27,366,292	25,607,278
Weighted average diluted common shares outstanding (in shares)		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		29,005,602	26,508,397
Restatement Adjustments | Dividend Income and Investment Gain (Loss) Classification Error
Revenues:
Services and fees		$ (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)		$ (19,732,000)	$ (21,163,000)
Trading (loss) income and fair value adjustments on loans		(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)		(166,131,000)	(47,341,000)
Interest income - Loans and securities lending		0	0	0	0	0	0	0	0	0	0	0		0	0
Revenues - Sale of goods		0	0	0	0	0	0	0	0	0	0	0		0	0
Total revenues		(28,246,000)	96,921,000	41,251,000	(21,796,000)	10,759,000	(17,804,000)	(157,022,000)	138,172,000	(174,826,000)	109,926,000	(164,067,000)		(185,863,000)	(68,504,000)
Operating expenses:
Direct cost of services		0	0	0	0	0	0	0	0	0	0	0		0	0
Cost of goods sold		0	0	0	0	0	0	0	0	0	0	0		0	0
Selling, general and administrative expenses		0	0	0	0	0	0	0	0	0	0	0		0	0
Restructuring charge		0									0				0
Impairment of tradenames															0
Interest expense - Securities lending and loan participations sold		0	0	0	0	0	0	0	0	0	0	0		0	0
Total operating expenses		0	0	0	0	0	0	0	0	0	0	0		0	0
Operating income		(28,246,000)	96,921,000	41,251,000	(21,796,000)	10,759,000	(17,804,000)	(157,022,000)	138,172,000	(174,826,000)	109,926,000	(164,067,000)		(185,863,000)	(68,504,000)
Other income (expense):
Interest income		0	0	0	0	0	0	0	0	0	0	0		0	0
Dividend income		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		19,732,000	21,163,000
Gain on equity method investment		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		166,131,000	47,341,000
Change in fair value of financial instruments and other		0	0	0	0	0	0	0	0	0	0	0		0
Income (loss) from equity method investments		0	0	0	0	0	0	0	0	0	0	0		0	0
Interest expense		0	0	0	0	0	0	0	0	0	0	0		0	0
(Loss) income before income taxes		0	0	0	0	0	0	0	0	0	0	0		0	0
Benefit from (provision for) income taxes		0	0	0	0	0	0	0	0	0	0	0		0	0
Net (loss) income		0	0	0	0	0	0	0	0	0	0	0		0	0
Net income (loss) attributable to noncontrolling interests and redeemable noncontrolling interests		0	0	0	0	0	0	0	0	0	0	0		0	0
Net (loss) income attributable to B. Riley Financial, Inc.		0	0	0	0	0	0	0	0	0	0	0		0	0
Preferred stock dividends		0	0	0	0	0	0	0	0	0	0	0		0	0
Net (loss) income available to common shareholders		0	0	0	0	0	0	0	0	0	0	0		0	0
Net (loss) income available to common shareholders		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		$ 0	$ 0