Note 7 - Financial Instruments (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Other Investments, Fair Value Disclosure	$ 37,558	$ 56,033
Margin Loan Collateral [Member]
Other Investments, Fair Value Disclosure	$ 11,863	$ 15,563

Amount of investments, other than trading securities, measured at fair value.

No definition available.

Name:	cohn_OtherInvestmentsFairValueDisclosure
Namespace Prefix:	cohn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant