Note 18 - Net Capital Requirements (Details Textual) $ in Thousands	Mar. 31, 2025 USD ($)
JVB [Member]
Broker-Dealer, Minimum Net Capital Required, Aggregate Indebtedness Standard	$ 250
Broker-Dealer, Net Capital	45,775
Broker-Dealer, Excess Net Capital, 1500 Percent, Aggregate Indebtedness Standard	45,525
CCFESA [Member]
Broker-Dealer, Minimum Net Capital Required, Aggregate Indebtedness Standard	670
Broker-Dealer, Net Capital	1,863
Broker-Dealer, Excess Net Capital, 1500 Percent, Aggregate Indebtedness Standard	$ 1,193

Amount of net capital in excess of minimum required net capital, calculated under Aggregate Indebtedness Standard.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Rule 15c3-1
-Number 240
-Section 15c3-1
-Publisher SEC

Name:	srt_ExcessNetCapitalAt1500Percent
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Minimum amount of net capital required to be maintained by broker-dealer and its subsidiary, calculated under Aggregate Indebtedness Standard.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Rule 15c3-1
-Number 240
-Section 15c3-1
-Publisher SEC

Name:	srt_MinimumNetCapitalRequired1
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of net capital of broker-dealer.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Rule 15c3-1
-Number 240
-Section 15c3-1
-Publisher SEC

Name:	dei_LegalEntityAxis=cohn_JVBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_LegalEntityAxis=cohn_CCFESAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: