Name:	ship_AutomaticExtensionPeriodOfAgreement
Namespace Prefix:	ship_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Contractual facility interest rate for financing receivable.

No definition available.

Name:	ship_FinancingReceivableInterestRate
Namespace Prefix:	ship_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Amount of gain (loss) on sale or disposal of property, plant and equipment assets to a related party.

No definition available.

Name:	ship_GainLossOnDispositionOfPropertyPlantEquipmentRelatedParty
Namespace Prefix:	ship_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Notice period for termination of agreement, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	ship_NoticePeriodForTerminationOfAgreement
Namespace Prefix:	ship_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The number of vessels whose technical management services were terminated during the period.

No definition available.

Name:	ship_NumberOfManagedVesselsWhoseTechnicalManagementServicesWereTerminated
Namespace Prefix:	ship_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Interest income on a loan receivable from related party.

No definition available.

Name:	ship_RelatedPartyInterestIncome
Namespace Prefix:	ship_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Percentage of the gross freight, demurrage and charter hire collected from the employment of vessels paid to a relate party as a commercial management fee.

No definition available.

Name:	ship_RelatedPartyTransactionCommercialManagementFee
Namespace Prefix:	ship_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Daily fee per vessel charged for the provision of technical, administrative, commercial, brokerage and certain other services.

No definition available.

Name:	ship_RelatedPartyTransactionDailyFixedAdministrationFee
Namespace Prefix:	ship_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Fixed monthly fees paid for arranging (directly or by subcontracting) for the crewing of the vessels, the day-to-day operations, inspections, maintenance, repairs, drydocking, purchasing, insurance and claims handling of vessels.

No definition available.

Name:	ship_RelatedPartyTransactionMonthlyFixedManagementFee
Namespace Prefix:	ship_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Number of vessels charged a monthly fixed management fee for services provided.

No definition available.

Name:	ship_RelatedPartyTransactionNumberOfVesselsChargedMonthlyFixedManagementFee
Namespace Prefix:	ship_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Percentage of the contract price of any vessel bought or sold paid as a fee to a related party.

No definition available.

Name:	ship_RelatedPartyTransactionPercentageOfContractPriceOnPurchaseOrSaleOfVessel
Namespace Prefix:	ship_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Term of short-term charter, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	ship_ShortTermCharterTerm
Namespace Prefix:	ship_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	ship_TransactionsWithRelatedPartyAbstract
Namespace Prefix:	ship_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amortized cost, before allowance for credit loss, of financing receivable classified as current. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477011/948-310-45-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483467/210-10-45-1

Name:	us-gaap_NotesAndLoansReceivableGrossCurrent
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

Amount of revenue that is not accounted for under Topic 606.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-SubTopic 10
-Topic 220
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

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

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

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

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

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

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

Name:	srt_ConsolidatedEntitiesAxis=ship_SeanergyShipmanagementCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

Name:	srt_ConsolidatedEntitiesAxis=ship_SeanergyManagementCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: