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

Increase (decrease) in the fair value of the conversion option of the Jelco Notes.

No definition available.

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

Percentage points added to the reference rate to compute the variable rate on the debt instrument based on certain emission reduction thresholds.

No definition available.

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

Amount of expense (income) related to adjustment to fair value of units issued to former related party.

No definition available.

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

Fair value of option granted to Jelco to purchase additional units pursuant to terms of the Omnibus Loans Agreement with Jelco Delta Holding Corp.

No definition available.

Name:	ship_FairValueOfOptionGrantedPerShare
Namespace Prefix:	ship_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

Fair value of units issued to Jelco pursuant to terms of the Omnibus Loans Agreement with Jelco Delta Holding Corp.

No definition available.

Name:	ship_FairValueOfUnitsIssued
Namespace Prefix:	ship_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

Percentage difference between the carrying value and fair market value of long-term debt.

No definition available.

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

Number of additional units that can be purchased in exchange for the settlement of principal under the Second Jelco Loan Facility in an amount equal to the aggregate purchase price of the units pursuant to terms of the Omnibus Loans Agreement with Jelco Delta Holding Corp.

No definition available.

Name:	ship_NumberOfAdditionalUnitsThatCanBePurchased
Namespace Prefix:	ship_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Sales price of additional units that can be purchased in exchange for the settlement of principal under the Second Jelco Loan Facility in an amount equal to the aggregate purchase price of the units pursuant to terms of the Omnibus Loans Agreement with Jelco Delta Holding Corp.

No definition available.

Name:	ship_SalesPriceOfAdditionalUnitsThatCanBePurchased
Namespace Prefix:	ship_
Data Type:	dtr-types:perShareItemType
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
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The price per share of the conversion feature embedded in the debt instrument.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6031898-161870

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

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

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

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

Price of a single share of a number of saleable stocks of a company.

No definition available.

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

Name:	us-gaap_DebtInstrumentAxis=ship_LoanAgreementDatedNovember122021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

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

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: