Long-Term Debt and Other Financial Liabilities, Evahline Sale and Leaseback (Details) - Evahline Sale and Leaseback [Member] $ in Thousands	6 Months Ended
Jun. 30, 2023 USD ($) Installment	Mar. 29, 2023 USD ($)
Sale and Leaseback Transaction [Abstract]
Financing amount		$ 19,000
Number of consecutive payment installments \| Installment	72
Installment payment	$ 264
Principal repayment term	6 years
Minimum value maintenance ratio to be maintained	1.20
SOFR [Member]
Sale and Leaseback Transaction [Abstract]
Term of variable rate	3 months
Margin on variable rate	2.80%

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

No definition available.

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Period Type:	duration

- Definition

Term of the interest rate that fluctuates over time as a result of an underlying benchmark interest rate or index, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The minimum threshold value maintenance ratio (expressed as a percentage) as defined in the additional clauses of the bareboat charter to be maintained by the Company.

+ References

No definition available.

+ Details

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Namespace Prefix:	ship_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments applied to principal.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

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.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

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

- Details

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