Percentage of voting equity interests acquired at the acquisition date in asset acquisition.

No definition available.

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Namespace Prefix:	cmre_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

+ References

No definition available.

+ Details

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

- Definition

This element represents the carrying capacity of vessels in TEUs (twenty-foot equivalet units) as at the end of each reporting period.

+ References

No definition available.

+ Details

Name:	cmre_CarryingCapacityOfVesselsAtPeriodEndTEU
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of asset acquired.

+ References

No definition available.

+ Details

Name:	cmre_NumberOfAssetAcquired
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents ownership percentage.

+ References

No definition available.

+ Details

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Namespace Prefix:	cmre_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents a special dividend amount.

+ References

No definition available.

+ Details

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

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of income (loss) for proportionate share of equity method investee's income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(10))
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-13

+ Details

Name:	us-gaap_PaymentsToAcquireEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Dividends received on equity and other investments during the current period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-16

+ Details

Name:	us-gaap_ProceedsFromDividendsReceived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=cmre_SykesMaritimeCoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=cmre_ArkadiaMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=cmre_PolarBrasilMember
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Data Type:	na
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Period Type:

- Details

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- Details

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- Details

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- Details

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- Details

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Note 10 - Equity Method Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 11, 2023	Dec. 05, 2023	May 12, 2023
Payments to Acquire Equity Method Investments	$ 1,274	$ 0	$ 0
Carrying Capacity of Vessels at Period End (TEU)	512,989	525,821
Income (Loss) from Equity Method Investments	$ 764	$ 2,296	$ 12,859
Vessel Owning Companies of Five Vessels Purchased from York [Member]
Number of Asset Acquired			5
Asset Acquistion, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net, Total			$ 141,040
Vessel Owning Companies of Five Vessels Purchased from York [Member] \| Minimum [Member]
Asset Acquisition, Percentage of Voting Interests Acquired			51.00%
Vessel Owning Companies of Five Vessels Purchased from York [Member] \| Maximum [Member]
Asset Acquisition, Percentage of Voting Interests Acquired			75.00%
Sykes Maritime Co. [Member]
Subsidiary, Ownership Percentage, Parent						100.00%
Arkadia [Member]
Asset Acquisition, Percentage of Voting Interests Acquired					51.00%
Carrying Capacity of Vessels at Period End (TEU)					1,550
Ownership Percentage				100.00%
Polar Brasil [Member]
Carrying Capacity of Vessels at Period End (TEU)						3,800
Geyer Maritime Co. [Member]
Proceeds from Dividends Received	1,274
Platt Maritime Co. [Member]
Payments to Acquire Equity Method Investments	980
Equity Method Investment, Ownership Percentage						49.00%
Platt Maritime Co. [Member] \| Arkadia [Member]
Equity Method Investment, Ownership Percentage						51.00%
Sykes Maritime Co. [Member]
Payments to Acquire Equity Method Investments	294
Sykes Maritime Co. [Member] \| York [Member]
Equity Method Investment, Ownership Percentage						51.00%
Goodway Maritime Co. [Member]
Special Dividend, Amount	$ 4,900
Equity Method Investment, Ownership Percentage	49.00%
Polar Argentina [Member]
Carrying Capacity of Vessels at Period End (TEU)						3,800
Steadman Maritime Co. [Member]
Proceeds from Dividends Received		$ 1,128	$ 15,190
Equity Method Investment, Ownership Percentage	49.00%