Vessel Revenue and Voyage Expenses, Net Trade Accounts Receivable Disaggregated by Revenue Source (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Vessel Revenue and Voyage Expenses [Abstract]
Accounts receivable trade, net	$ 720	$ 0
Current portion of deferred revenue	2,232	7,735
Non-current of deferred revenue	35	$ 538
Deferred revenue recognized	$ 7,735

Amount of revenue recognized that was previously included in balance of deferred income excluding obligation to transfer product and service to customer for which consideration has been received or is receivable.

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4531-111522

+ Details

Name:	us-gaap_AccountsReceivableNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of deferred income excluding obligation to transfer product and service to customer for which consideration has been received or is receivable, classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 25
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=28183603&loc=d3e692-112598

+ Details

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

- Definition

Amount of deferred income excluding obligation to transfer product and service to customer for which consideration has been received or is receivable, classified as noncurrent.

+ References

+ Details

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