Name:	ctrm_FundingPeriodForAdvanceToCoverVesselDailyOperatingCosts
Namespace Prefix:	ctrm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The number of vessels acquired by the entity during the period.

No definition available.

Name:	ctrm_NumberOfVesselsAcquired
Namespace Prefix:	ctrm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of vessels sold by the entity during the period.

No definition available.

Name:	ctrm_NumberOfVesselsSold
Namespace Prefix:	ctrm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The percentage of the gross charter hire, freight and the ballast bonus earned under a charter charged as a commission to the Company by a related party.

No definition available.

Name:	ctrm_RelatedPartyTransactionCommissionRate
Namespace Prefix:	ctrm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

A commission charged by a related party in connection with each vessel sale and purchase transaction.

No definition available.

Name:	ctrm_RelatedPartyTransactionCommissionRateOnEachVesselSaleAndPurchaseTransaction
Namespace Prefix:	ctrm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	ctrm_RelatedPartyTransactionDueFromToRelatedPartiesCurrentAbstract
Namespace Prefix:	ctrm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fixed daily fee charged by a related party to provide a wide range of shipping services such as crew management, technical management, operational employment management, insurance arrangements, provisioning, bunkering, accounting services, general administration and audit support.

No definition available.

Name:	ctrm_RelatedPartyTransactionFixedDailyFee
Namespace Prefix:	ctrm_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

Recovery fee multiplier applied to the total amount of the flat management fee calculated on an annual basis under an agreement with a related party.

No definition available.

Name:	ctrm_RelatedPartyTransactionManagementRecoveryFeeMultiplier
Namespace Prefix:	ctrm_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

Termination fee multiplier applied to the total amount of the flat management fee and the per vessel management fee calculated on an annual basis under an agreement with a related party.

No definition available.

Name:	ctrm_RelatedPartyTransactionManagementTerminationFeeMultiplier
Namespace Prefix:	ctrm_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

Fixed quarterly fee charged by a related party to provide a shipping related administrative services.

No definition available.

Name:	ctrm_RelatedPartyTransactionQuarterlyManagementFee
Namespace Prefix:	ctrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Term of related party agreement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	ctrm_RelatedPartyTransactionRenewalTermOfAgreement
Namespace Prefix:	ctrm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Amount of commission charged by related party for any sale or purchase of vessels for the Company.

No definition available.

Name:	ctrm_RelatedPartyTransactionSaleAndPurchaseCommission
Namespace Prefix:	ctrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Term of related party agreement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	ctrm_RelatedPartyTransactionTermOfAgreement
Namespace Prefix:	ctrm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Amount of liabilities classified as other, due within one year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481372/852-10-55-10

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Name:	us-gaap_OtherLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount, after allowance for credit loss, of receivable classified as other and noncurrent.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Name:	us-gaap_OtherReceivableAfterAllowanceForCreditLossNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount, after allowance, of receivables classified as other, due within one year or the operating cycle, if longer.

No definition available.

Name:	us-gaap_OtherReceivablesNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	srt_CounterpartyNameAxis=ctrm_CastorShipsSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ctrm_PanamaxVesselMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ctrm_KamsarmaxVesselMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionAxis=ctrm_AmendedCastorShipManagementAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ctrm_DryBulkCarrierMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_RelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ctrm_VesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_IncomeStatementLocationAxis=ctrm_GainLossOnSaleOfPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionAxis=ctrm_CastorShipManagementAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ctrm_ContainershipAndDryBulkCarrierMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ctrm_TankerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionAxis=ctrm_WorkingCapitalGuaranteeAdvancesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionAxis=ctrm_OperatingExpensesPaymentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: