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Basis of Presentation and General Information, Vessels Acquisitions - 20F (Details) |  |  |  | 12 Months Ended
--- | --- | --- | --- | ---
Aug. 06, 2015 Vessel | Mar. 19, 2015 t | Dec. 23, 2014 t | Dec. 31, 2015 Vessel
Vessel Acquisitions [Abstract] |  |  |  |
Number of vessels acquired |  |  |  | 8
Leadership [Member] |  |  |  |
Vessel Acquisitions [Abstract] |  |  |  |
Dead weight tonnage | t |  | 171,199 | 171,199 |
Dry Bulk Vessel [Member] |  |  |  |
Vessel Acquisitions [Abstract] |  |  |  |
Number of vessels acquired | 7 |  |  |

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- Definition Deadweight tonnage (DWT) is a measure of vessels capacity in weight, and does not include the weight of the vessel. + References No definition available. + Details
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- Definition The number of vessels acquired during the period. + References No definition available. + Details
Name: | ship_NumberOfVesselsAcquired
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Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=ship_DryBulkVesselMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |