Face amount of the debt instrument that is available for borrowing at time the agreement is executed and/or amended.

No definition available.

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Namespace Prefix:	ship_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The number of consecutive payment installments that can be partially deferred prior to the balloon installment.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of periodic installments paid.

+ References

No definition available.

+ Details

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

- Definition

The percentage of excess earnings (as defined in the loan agreement) to be applied towards payment of deferred installments until the deferred amount is fully paid.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The threshold ratio (expressed as a percentage) of earnings before interest, taxes, depreciation and amortization (EBITDA) to net interest expense, as defined in the loan facility.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

The leverage ratio (expressed as a percentage) as defined in the loan facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	ship_
Data Type:	xbrli:pureItemType
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- Definition

Percentage of net income limit for the declaration of dividends.

+ References

No definition available.

+ Details

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Namespace Prefix:	ship_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of time cash and marketable securities are equal or greater than the amount required to meet the Company's consolidated installment and debt interest payments for purposes of distributing dividends, 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

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:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

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

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

Amount of payment greater than the preceding installment payments to be paid at final maturity date of debt.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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Balance Type:
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- Details

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- Details

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Namespace Prefix:
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- Details

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Long-Term Debt and Financial Liabilities, Loan dated March 6, 2015 (Details) - Loan Agreement dated March 6, 2015 [Member] $ in Thousands			6 Months Ended
	Jul. 28, 2016 Installment	Mar. 06, 2015 USD ($)	Jun. 30, 2018 USD ($) Installment	Dec. 23, 2015
Secured Credit Facilities [Abstract]
Borrowing capacity		$ 8,750
Percentage of net income limit for declaring dividends		50.00%
Term to meet consolidated installment and debt interest payments			18 months
Number of consecutive payment installments that can be partially deferred \| Installment	4
Percentage of excess earnings to be applied towards payment of deferred installments	80.00%
Number of installments paid \| Installment			13
Frequency of periodic payment			Quarterly
Installment payment			$ 250
Balloon payment			$ 4,453
Maturity date			Mar. 17, 2020
Minimum [Member]
Secured Credit Facilities [Abstract]
EBITDA to net interest expense ratio				2
Maximum [Member]
Secured Credit Facilities [Abstract]
Leverage ratio				0.75
LIBOR [Member]
Secured Credit Facilities [Abstract]
Margin on variable rate		3.75%