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

The number of consecutive, periodic payment installments in which the debt is to be repaid.

No definition available.

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

Face amount of financial liability at time of sale and leaseback agreement.

No definition available.

Name:	ship_FinancialLiabilityFaceAmount
Namespace Prefix:	ship_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Term of charter on a bareboat basis under the sale leaseback transaction, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

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

The implied average applicable interest rate under the transaction involving the sale of the property to another party and the lease of the property back to the seller.

No definition available.

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

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Description of the frequency of periodic payments (monthly, quarterly, annual).

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-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_DebtInstrumentFrequencyOfPeriodicPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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Period Type:	duration

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Publisher FASB
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Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

Amount of the required periodic payments applied to principal.

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

Amount of payment greater than the preceding installment payments to be paid at final maturity date of debt.

No definition available.

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

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

No definition available.

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

- References

No definition available.