Monthly bareboat rate charged for the vessel to the lessee under a finance lease.

No definition available.

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

- Definition

Purchase price of vessel at the end of the bareboat period by the lessee under a finance lease.

+ References

No definition available.

+ Details

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

- Definition

Number of installment payments to be made for the construction price of a new vessel.

+ References

No definition available.

+ Details

Name:	ship_NumberOfInstallmentPayments
Namespace Prefix:	ship_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the construction of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

No definition available.

+ Details

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

- Definition

Percentage of purchase price of vessel paid upon execution of the agreement.

+ References

No definition available.

+ Details

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

- Definition

Percentage of purchase price of vessel payable during the first fifteen (15) months following the execution of the agreement.

+ References

No definition available.

+ Details

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

- Definition

Percentage of purchase price of vessel payable during the first thirty (30) months following the execution of the agreement.

+ References

No definition available.

+ Details

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

- Definition

Percentage of purchase price of vessel payable upon delivery of the vessel.

+ References

No definition available.

+ Details

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

- Definition

The percentage of the vessel purchase price paid.

+ References

No definition available.

+ Details

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

- Definition

Period after signing bareboat charter agreement to pay an additional down payment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Purchase price of long-lived, physical assets used in the normal conduct of business and not intended for resale.

+ References

No definition available.

+ Details

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

- Definition

Period after execution of contract to pay 45% of the purchase price of the vessel, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Period after execution of contract to pay 40% of the purchase price of the vessel, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Maximum weight of cargo and supplies that a vessel can carry, excluding the ship's own empty weight.

+ References

No definition available.

+ Details

Name:	ship_VesselCapacity
Namespace Prefix:	ship_
Data Type:	dtr-types:massItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Term of lessee's finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

Name:	us-gaap_LesseeFinanceLeaseTermOfContract1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

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

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ship_Newbuilding7Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ship_Newbuilding6Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ship_Newbuilding2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ship_Newbuilding3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ship_Newbuilding4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Vessels under construction (Details) $ in Thousands							3 Months Ended	6 Months Ended
Vessels under construction (Details) $ in Thousands	Feb. 25, 2027 USD ($)	Jun. 01, 2026 USD ($) Installment t	Apr. 09, 2026 USD ($) Installment t	Feb. 26, 2026 USD ($) Installment t	Feb. 25, 2026 USD ($) t	Jan. 30, 2026 USD ($) Installment t	Mar. 31, 2029 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)
Vessels under construction [Abstract]
Payment for vessels under construction								$ 70,022	$ 0
Down payment								$ 1,928	$ 35,325
Newbuilding 7 [Member]
Vessels under construction [Abstract]
Vessel capacity \| t		181,000
Contract price		$ 80,000
Number of installment payments \| Installment		5
Percentage of purchase price payable during first 30 months		40.00%
Term for payment of 40% of purchase price								30 months
Percentage of purchase price payable upon delivery of vessel		60.00%
Percentage of purchase price paid								5.00%
Newbuilding 6 [Member]
Vessels under construction [Abstract]
Vessel capacity \| t			181,500
Contract price			$ 77,857
Number of installment payments \| Installment			5
Percentage of purchase price payable during first 15 months			45.00%
Term for payment of 45% of purchase price								15 months
Percentage of purchase price payable upon delivery of vessel			55.00%
Payment for vessels under construction								$ 0
Newbuilding 2 [Member]
Vessels under construction [Abstract]
Vessel capacity \| t				181,500
Contract price				$ 80,100
Number of installment payments \| Installment				2
Percentage of purchase price paid upon execution of agreement				20.00%
Percentage of purchase price payable upon delivery of vessel				80.00%
Percentage of purchase price paid								20.00%
Newbuilding 3 [Member]
Vessels under construction [Abstract]
Vessel capacity \| t					181,500
Term of bareboat charter agreement								10 years
Down payment					$ 3,875
Period after signing bareboat charter agreement to pay additional down payment								1 year
Monthly bareboat rate					295
Purchase price of vessel at end of bareboat period					$ 26,970
Newbuilding 3 [Member] \| Plan [Member]
Vessels under construction [Abstract]
Down payment	$ 7,750						$ 3,875
Newbuilding 4 [Member]
Vessels under construction [Abstract]
Vessel capacity \| t						181,500
Contract price						$ 75,159
Number of installment payments \| Installment						5
Percentage of purchase price payable during first 15 months						45.00%
Term for payment of 45% of purchase price								15 months
Percentage of purchase price payable upon delivery of vessel						55.00%
Percentage of purchase price paid								25.00%