Note 9 - Fair Value Disclosures (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Investment Sold, Not yet Purchased, Gain (Loss), Fair Value	$ 35,421	$ 43,413	$ 1,080
Other Investment Sold, Not yet Purchased, Gain (Loss)	$ 830	$ 1,063	$ (0)

Represents realized and unrealized gain (loss) for other investment sold not yet purchased.

No definition available.

Name:	cohn_OtherInvestmentSoldNotYetPurchasedGainLoss
Namespace Prefix:	cohn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration