Name:	gnrt_AggregatePrincipalAmountOfOtherDebtUndergoingChangeOfControlThatTriggersChangeOfControlToDebtFacility
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Represents the consolidated debt leverage ratio under the debt instrument.

No definition available.

Name:	gnrt_DebtLeverageRatio
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Data Type:	xbrli:pureItemType
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Period Type:	duration

Represents number of additional Term loan tranches

No definition available.

Name:	gnrt_NumberOfAdditionalTermLoans
Namespace Prefix:	gnrt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of newbuilding-owning subsidiaries acquired by the Company in the merger

No definition available.

Name:	gnrt_NumberOfNewbuildingOwningSubsidiaries
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Data Type:	xbrli:integerItemType
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Represents the number of completed vessels delivered during the period.

No definition available.

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

Represents the number of vessels to be delivered during the period.

No definition available.

Name:	gnrt_NumberOfVesselsToBeDeliveredUnderContract
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Data Type:	xbrli:integerItemType
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Number of vessels under building contract.

No definition available.

Name:	gnrt_NumberOfVesselsUnderBuildingContract
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Percentage of balloon payment to amount of loan.

No definition available.

Name:	gnrt_PercentageOfBalloonPaymentToLoan
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of each installment amount to Vessel Loan.

No definition available.

Name:	gnrt_PercentageOfEachInstallmentAmountOfLoan
Namespace Prefix:	gnrt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Incremental percentage increase (decrease) in the stated rate on a debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentInterestRateIncreaseDecrease
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Data Type:	num:percentItemType
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_DebtInstrumentTerm
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	na
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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	gnrt_VesselsByNameAxis=gnrt_Gener8ChiotisAndGener8MiltiadesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
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