Note 10 - Long-term Debt - Financing Costs Included in Loan Balances (Details) $ in Thousands	6 Months Ended
Jun. 30, 2025 USD ($)
Balance, at beginning of the period	$ 11,396
Additions	455
Amortization and write-off	(1,943)
Balance, at end of the period	9,908
Less: Current portion of financing costs	(3,161)
Financing costs, non-current portion	$ 6,747

Finance costs that have been incurred and deferred during the period.

No definition available.

Name:	cmre_DeferredFinanceCostsAdditions
Namespace Prefix:	cmre_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of amortization and write-offs related to deferred finance costs.

No definition available.

Name:	cmre_DeferredFinanceCostsAmortizationAndWriteoff
Namespace Prefix:	cmre_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount, after accumulated amortization, of debt and capital lease issuance costs classified as current.

No definition available.

Name:	cmre_DeferredFinanceCostsIncludingCapitalLeasesNetCurrent
Namespace Prefix:	cmre_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount, after accumulated amortization, of debt and capital lease issuance costs classified as noncurrent.

No definition available.

Name:	cmre_DeferredFinanceCostsIncludingCaptialLeaseNetNoncurrent
Namespace Prefix:	cmre_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount, after accumulated amortization, of debt and capital lease issuance costs.

No definition available.

Name:	cmre_DeferredFinancingCostsIncludingCapitalLeaseNet
Namespace Prefix:	cmre_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant