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Subsequent Events (Details) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2018 USD ($) vessel | Jun. 30, 2018 vessel
Subsequent Event [Line Items] |  |
Number of T-ATS vessels | 1 |
Number of additional vessels | 7 | 7
U.S. Navy |  |
Subsequent Event [Line Items] |  |
Construction in progress | $ | $ 63.6 |

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- Definition Construction In Progress, Number Of Additional Vessels + References No definition available. + Details
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Namespace Prefix: | gifi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Construction In Progress, Number Of T-ATS Vessels + References No definition available. + Details
Name: | gifi_ConstructionInProgressNumberOfTATSVessels
Namespace Prefix: | gifi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
Name: | us-gaap_ConstructionInProgressGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_CounterpartyNameAxis=gifi_U.S.NavyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |