Name:	ship_DebtInstrumentMinimumLiquidityRequirementInEarningsAccount
Namespace Prefix:	ship_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

The required security cover threshold (expressed as a percentage) as defined in the loan facility agreement.

No definition available.

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

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	dtr-types:percentItemType
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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.

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

Face (par) amount of debt instrument at time of issuance.

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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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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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

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	us-gaap_SecuredLongtermDebtCurrentAndNoncurrentAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Name:	us-gaap_DebtInstrumentAxis=ship_June2022AlphaBankLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=ship_DebtInstrumentRedemptionFirstFourInstallmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=ship_DebtInstrumentRedemptionNextTwelveInstallmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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