Note 22 - Segment and Geographic Information - Statements of Operations Information (Details) - USD ($) $ in Thousands		3 Months Ended						9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Net trading		$ 16,957			$ 8,479			$ 55,524	$ 25,873
Principal transactions and other income		2,768			520			2,783	1,688
Revenues, Total		21,856			11,267			63,745	33,576
Salaries/Wages		10,965			7,017			36,423	19,813
Other Operating Expense		4,819			4,693			14,886	13,756
Goodwill, Impairment Loss								7,883
Total operating expenses		15,784			11,710			59,192	33,569
Operating income (loss)		6,072			(443)			4,553	7
Interest income (expense)		(1,952)			(1,536)			(7,638)	(5,329)
Income (loss) from equity method affiliates		(1,371)			(109)			(2,711)	(365)
Income (loss) before income taxes		2,749			(2,088)			(5,796)	(5,687)
Income tax expense (benefit)		(594)			(170)			(623)	(917)
Net income (loss)		3,343	$ 3,269	$ (11,785)	(1,918)	$ (1,028)	$ (1,824)	(5,173)	(4,770)
Less: Net income (loss) attributable to the non-controlling interest		1,688			(702)			(4,627)	(1,942)
Net income (loss) attributable to Cohen & Company Inc.		1,655			(1,216)			(546)	(2,828)
Depreciation and amortization (included in total operating expense)		85			80			249	239
Asset Management [Member]
Revenues		1,631			2,018			4,938	5,765
New Issue and Advisory [Member]
Revenues		500			250			500	250
Operating Segments [Member]
Net trading		16,957			8,479			55,524	25,873
Principal transactions and other income		2,768			520			2,783	1,688
Revenues, Total		21,856			11,267			63,745	33,576
Salaries/Wages		9,931			6,168			33,102	17,396
Other Operating Expense		3,707			3,706			11,115	10,636
Goodwill, Impairment Loss								7,883
Total operating expenses		13,638			9,874			52,100	28,032
Operating income (loss)		8,218			1,393			11,645	5,544
Interest income (expense)		(345)			(36)			(754)	(140)
Income (loss) from equity method affiliates		(1,371)			(109)			(2,711)	(365)
Income (loss) before income taxes		6,502			1,248			8,180	5,039
Income tax expense (benefit)
Net income (loss)		6,502			1,248			8,180	5,039
Less: Net income (loss) attributable to the non-controlling interest
Net income (loss) attributable to Cohen & Company Inc.		6,502			1,248			8,180	5,039
Depreciation and amortization (included in total operating expense)		5			6			15	15
Operating Segments [Member] | Asset Management [Member]
Revenues		1,631			2,018			4,938	5,765
Operating Segments [Member] | New Issue and Advisory [Member]
Revenues		500			250			500	250
Operating Segments [Member] | Capital Markets [Member]
Net trading		16,957			8,479			55,524	25,873
Principal transactions and other income								6	2
Revenues, Total		17,457			8,729			56,030	26,125
Salaries/Wages		8,880			5,148			29,840	14,323
Other Operating Expense		3,074			3,013			9,309	8,515
Goodwill, Impairment Loss								7,883
Total operating expenses		11,954			8,161			47,032	22,838
Operating income (loss)		5,503			568			8,998	3,287
Interest income (expense)		(345)			(36)			(754)	(140)
Income (loss) from equity method affiliates
Income (loss) before income taxes		5,158			532			8,244	3,147
Income tax expense (benefit)
Net income (loss)		5,158			532			8,244	3,147
Less: Net income (loss) attributable to the non-controlling interest
Net income (loss) attributable to Cohen & Company Inc.		5,158			532			8,244	3,147
Depreciation and amortization (included in total operating expense)		4			5			13	13
Operating Segments [Member] | Capital Markets [Member] | Asset Management [Member]
Revenues
Operating Segments [Member] | Capital Markets [Member] | New Issue and Advisory [Member]
Revenues		500			250			500	250
Operating Segments [Member] | Asset Management Segment [Member]
Net trading
Principal transactions and other income		151			157			365	379
Revenues, Total		1,782			2,175			5,303	6,144
Salaries/Wages		1,051			1,020			3,262	3,073
Other Operating Expense		583			592			1,654	1,821
Goodwill, Impairment Loss
Total operating expenses		1,634			1,612			4,916	4,894
Operating income (loss)		148			563			387	1,250
Interest income (expense)
Income (loss) from equity method affiliates		217						517
Income (loss) before income taxes		365			563			904	1,250
Income tax expense (benefit)
Net income (loss)		365			563			904	1,250
Less: Net income (loss) attributable to the non-controlling interest
Net income (loss) attributable to Cohen & Company Inc.		365			563			904	1,250
Depreciation and amortization (included in total operating expense)		1			1			2	2
Operating Segments [Member] | Asset Management Segment [Member] | Asset Management [Member]
Revenues		1,631			2,018			4,938	5,765
Operating Segments [Member] | Asset Management Segment [Member] | New Issue and Advisory [Member]
Revenues
Operating Segments [Member] | Principal Investing [Member]
Net trading
Principal transactions and other income		2,617			363			2,412	1,307
Revenues, Total		2,617			363			2,412	1,307
Salaries/Wages
Other Operating Expense		50			101			152	300
Goodwill, Impairment Loss
Total operating expenses		50			101			152	300
Operating income (loss)		2,567			262			2,260	1,007
Interest income (expense)
Income (loss) from equity method affiliates		(1,588)			(109)			(3,228)	(365)
Income (loss) before income taxes		979			153			(968)	642
Income tax expense (benefit)
Net income (loss)		979			153			(968)	642
Less: Net income (loss) attributable to the non-controlling interest
Net income (loss) attributable to Cohen & Company Inc.		979			153			(968)	642
Depreciation and amortization (included in total operating expense)
Operating Segments [Member] | Principal Investing [Member] | Asset Management [Member]
Revenues
Operating Segments [Member] | Principal Investing [Member] | New Issue and Advisory [Member]
Revenues
Segment Reconciling Items [Member]
Net trading	[1]
Principal transactions and other income	[1]
Revenues, Total	[1]
Salaries/Wages	[1]	1,034			849			3,321	2,417
Other Operating Expense		1,112			987			3,771	3,120
Goodwill, Impairment Loss	[1]
Total operating expenses	[1]	2,146			1,836			7,092	5,537
Operating income (loss)	[1]	(2,146)			(1,836)			(7,092)	(5,537)
Interest income (expense)	[1]	(1,607)			(1,500)			(6,884)	(5,189)
Income (loss) from equity method affiliates	[1]
Income (loss) before income taxes	[1]	(3,753)			(3,336)			(13,976)	(10,726)
Income tax expense (benefit)	[1]	(594)			(170)			(623)	(917)
Net income (loss)	[1]	(3,159)			(3,166)			(13,353)	(9,809)
Less: Net income (loss) attributable to the non-controlling interest	[1]	1,688			(702)			(4,627)	(1,942)
Net income (loss) attributable to Cohen & Company Inc.	[1]	(4,847)			(2,464)			(8,726)	(7,867)
Depreciation and amortization (included in total operating expense)	[1]	80			74			234	224
Segment Reconciling Items [Member] | Asset Management [Member]
Revenues	[1]
Segment Reconciling Items [Member] | New Issue and Advisory [Member]
Revenues	[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.