Note 29 - Segment and Geographic Information - Statements of Operations Information (Details) - USD ($) $ in Thousands		1 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net trading										$ 73,611	$ 38,172	$ 29,298
Principal transactions and other income										45,506	2,103	4,573
Revenues, Total		$ 66,365	$ 21,856	$ 24,119	$ 17,770	$ 16,090	$ 11,267	$ 11,169	$ 11,140	130,110	49,666	49,386
Compensation and benefits		23,479	10,965	11,324	14,134	6,159	7,017	6,432	6,364	59,902	25,972	25,385
Other operating expense										19,997	19,653	20,342
Goodwill, Impairment Loss					7,883					7,883
Total operating expenses		28,590	15,784	16,193	27,215	12,056	11,710	10,651	11,208	87,782	45,625	45,727
Operating income / (loss)		37,775	6,072	7,926	(9,445)	4,034	(443)	518	(68)	42,328	4,041	3,659
Interest expense (income), net										(9,589)	(7,584)	(8,487)
Earnings / (loss) realized		(244)	(1,371)	(1,233)	(107)	(188)	(109)	(248)	(8)	(2,955)	(553)
Income / (loss) before income taxes		35,580	2,749	3,612	(12,157)	1,591	(2,088)	(1,669)	(1,930)	29,784	(4,096)	(4,828)
Income tax expense / (benefit)		(8,046)	(594)	343	(372)	394	(170)	(641)	(106)	(8,669)	(523)	(841)
Net income / (loss)		43,626	3,343	3,269	(11,785)	1,197	(1,918)	(1,028)	(1,824)	38,453	(3,573)	(3,987)
Less: Net income / (loss) attributable to the non-controlling interest										24,248	(1,519)	(1,524)
Net income / (loss) attributable to Cohen & Company Inc.		14,751	1,655	901	(3,102)	774	(1,216)	(410)	(1,202)	14,205	(2,054)	(2,463)
Depreciation, Depletion and Amortization, Nonproduction, Total		85	85	84	80	79	80	78	81	334	318	261
Compensation and benefits		23,479	10,965	11,324	14,134	6,159	7,017	6,432	6,364	59,902	25,972	25,385
Other Operating Expense										19,997	19,653	20,342
Impairment of goodwill					$ 7,883					7,883
Asset Management [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total										8,759	7,560	12,536
New Issue and Advisory [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total										2,234	1,831	2,979
Operating Segments [Member]
Net trading										73,611	38,172	29,298
Principal transactions and other income										45,506	2,103	4,573
Revenues, Total										130,110	49,666	49,386
Compensation and benefits										53,101	23,380	22,431
Other operating expense										14,756	15,112	16,601
Goodwill, Impairment Loss										7,883
Total operating expenses										75,740	38,492	39,032
Operating income / (loss)										54,370	11,174	10,354
Interest expense (income), net										(997)	(175)	(236)
Earnings / (loss) realized										(2,955)	(553)
Income / (loss) before income taxes										50,418	10,446	10,118
Income tax expense / (benefit)
Net income / (loss)										50,418	10,446	10,118
Less: Net income / (loss) attributable to the non-controlling interest										10,048	(288)
Net income / (loss) attributable to Cohen & Company Inc.										40,370	10,734	10,118
Depreciation, Depletion and Amortization, Nonproduction, Total										21	21	52
Compensation and benefits										53,101	23,380	22,431
Other Operating Expense										14,756	15,112	16,601
Impairment of goodwill										7,883
Operating Segments [Member] | Asset Management [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total										8,759	7,560	12,536
Operating Segments [Member] | New Issue and Advisory [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total										2,234	1,831	2,979
Operating Segments [Member] | Capital Markets [Member]
Net trading										73,611	38,172	29,298
Principal transactions and other income										3	1	39
Revenues, Total										75,848	40,004	32,316
Compensation and benefits										36,092	18,575	17,539
Other operating expense										12,546	12,257	12,410
Goodwill, Impairment Loss										7,883
Total operating expenses										56,521	30,832	29,949
Operating income / (loss)										19,327	9,172	2,367
Interest expense (income), net										(997)	(175)	(236)
Earnings / (loss) realized
Income / (loss) before income taxes										18,330	8,997	2,131
Income tax expense / (benefit)
Net income / (loss)										18,330	8,997	2,131
Less: Net income / (loss) attributable to the non-controlling interest
Net income / (loss) attributable to Cohen & Company Inc.										18,330	8,997	2,131
Depreciation, Depletion and Amortization, Nonproduction, Total										18	18	48
Compensation and benefits										36,092	18,575	17,539
Other Operating Expense										12,546	12,257	12,410
Impairment of goodwill										7,883
Operating Segments [Member] | Capital Markets [Member] | Asset Management [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total
Operating Segments [Member] | Capital Markets [Member] | New Issue and Advisory [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total										2,234	1,831	2,979
Operating Segments [Member] | Asset Management Segment [Member]
Net trading
Principal transactions and other income										639	530	678
Revenues, Total										9,398	8,090	13,214
Compensation and benefits										5,309	4,805	4,571
Other operating expense										2,042	2,456	3,800
Goodwill, Impairment Loss
Total operating expenses										7,351	7,261	8,371
Operating income / (loss)										2,047	829	4,843
Interest expense (income), net
Earnings / (loss) realized										639
Income / (loss) before income taxes										2,686	829	4,843
Income tax expense / (benefit)
Net income / (loss)										2,686	829	4,843
Less: Net income / (loss) attributable to the non-controlling interest										1,408
Net income / (loss) attributable to Cohen & Company Inc.										1,278	829	4,843
Depreciation, Depletion and Amortization, Nonproduction, Total										3	3	4
Compensation and benefits										5,309	4,805	4,571
Other Operating Expense										2,042	2,456	3,800
Impairment of goodwill
Operating Segments [Member] | Asset Management Segment [Member] | Asset Management [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total										8,759	7,560	12,536
Operating Segments [Member] | Asset Management Segment [Member] | New Issue and Advisory [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total
Operating Segments [Member] | Principal Investing [Member]
Net trading
Principal transactions and other income										44,864	1,572	3,856
Revenues, Total										44,864	1,572	3,856
Compensation and benefits										11,700		321
Other operating expense										168	399	391
Goodwill, Impairment Loss
Total operating expenses										11,868	399	712
Operating income / (loss)										32,996	1,173	3,144
Interest expense (income), net
Earnings / (loss) realized										(3,594)	(553)
Income / (loss) before income taxes										29,402	620	3,144
Income tax expense / (benefit)
Net income / (loss)										29,402	620	3,144
Less: Net income / (loss) attributable to the non-controlling interest										8,640	(288)
Net income / (loss) attributable to Cohen & Company Inc.										20,762	908	3,144
Depreciation, Depletion and Amortization, Nonproduction, Total
Compensation and benefits										11,700		321
Other Operating Expense										168	399	391
Impairment of goodwill
Operating Segments [Member] | Principal Investing [Member] | Asset Management [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total
Operating Segments [Member] | Principal Investing [Member] | New Issue and Advisory [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total
Segment Reconciling Items [Member]
Net trading	[1]
Principal transactions and other income	[1]
Revenues, Total	[1]
Compensation and benefits	[1]									6,801	2,592	2,954
Other operating expense	[1]									5,241	4,541	3,741
Goodwill, Impairment Loss	[1]
Total operating expenses	[1]									12,042	7,133	6,695
Operating income / (loss)	[1]									(12,042)	(7,133)	(6,695)
Interest expense (income), net	[1]									(8,592)	(7,409)	(8,251)
Earnings / (loss) realized	[1]
Income / (loss) before income taxes	[1]									(20,634)	(14,542)	(14,946)
Income tax expense / (benefit)	[1]									(8,669)	(523)	(841)
Net income / (loss)	[1]									(11,965)	(14,019)	(14,105)
Less: Net income / (loss) attributable to the non-controlling interest	[1]									14,200	(1,231)	(1,524)
Net income / (loss) attributable to Cohen & Company Inc.	[1]									(26,165)	(12,788)	(12,581)
Depreciation, Depletion and Amortization, Nonproduction, Total	[1]									313	297	209
Compensation and benefits	[1]									6,801	2,592	2,954
Other Operating Expense	[1]									5,241	4,541	3,741
Impairment of goodwill	[1]
Segment Reconciling Items [Member] | Asset Management [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total	[1]
Segment Reconciling Items [Member] | New Issue and Advisory [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total	[1]

[1] Unallocated includes certain expenses incurred by indirect overhead and support departments (such as the executive, finance, legal, information technology, human resources, risk, compliance and other similar overhead and support departments). Some of the items not allocated include: (1) operating expenses (such as cash compensation and benefits, equity-based compensation expense, professional fees, travel and entertainment, consulting fees, and rent) related to support departments excluding certain departments that directly support the Capital Markets business segment; (2) interest expense on debt; and (3) income taxes. Management does not consider these items necessary for an understanding of the operating results of these business segments and such amounts are excluded in business segment reporting to the chief operating decision maker.