Represents the ratio of the final balloon payment to the original loan amount.

No definition available.

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

- Definition

Represents the percentage of the price or fair market value that determines the amount that is able to be borrowed for the purchase of vessels. The final amount borrowed is based on the lowest of the various measures.

+ References

No definition available.

+ Details

Name:	gnrt_BorrowingAmountAsPercentageOfVesselPriceOrFairMarketValue
Namespace Prefix:	gnrt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the amended contract price of the vessel.

+ References

No definition available.

+ Details

Name:	gnrt_BuildingContractAmendedContractPrice
Namespace Prefix:	gnrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the amended final installment payment of the vessel.

+ References

No definition available.

+ Details

Name:	gnrt_BuildingContractAmendedFinalInstallment
Namespace Prefix:	gnrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the amount of damages due to late delivery of Vessel by builder per the Building Contract.

+ References

No definition available.

+ Details

Name:	gnrt_BuildingContractDamagesDue
Namespace Prefix:	gnrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the original contract price of the vessel per the Building Contract.

+ References

No definition available.

+ Details

Name:	gnrt_BuildingContractOriginalContractPrice
Namespace Prefix:	gnrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the original final installment payment due for the vessel.

+ References

No definition available.

+ Details

Name:	gnrt_BuildingContractOriginalFinalInstallment
Namespace Prefix:	gnrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the amount of building contract price reduction.

+ References

No definition available.

+ Details

Name:	gnrt_BuildingContractPriceReduction
Namespace Prefix:	gnrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the number of periodic or installment payments required under the terms of borrowing.

+ References

No definition available.

+ Details

Name:	gnrt_DebtInstrumentNumberOfPeriodicPayments
Namespace Prefix:	gnrt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of vessels that are pledged as security on a first lien basis on outstanding debt.

+ References

No definition available.

+ Details

Name:	gnrt_NumberOfVesselsPledgedAsSecurityOnDebt
Namespace Prefix:	gnrt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of vessels under building contract.

+ References

No definition available.

+ Details

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

- Definition

Percentage of minimum liquidity based on amount outstanding in the Company’s debt service reserve account.

+ References

No definition available.

+ Details

Name:	gnrt_PercentageOfMinimumLiquidityBasedOnAmountOutstandingInDebtServiceReserveAccount
Namespace Prefix:	gnrt_
Data Type:	num:percentItemType
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

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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

+ Details

Name:	us-gaap_DebtInstrumentFrequencyOfPeriodicPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentInterestRateIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

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.

+ References

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

+ Details

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

- Details

Name:	gnrt_VesselsByNameAxis=gnrt_Gener8NestorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=gnrt_TermLoanFacilityKoreanExportCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=gnrt_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_LenderTrancheAxis=gnrt_CommercialTrancheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_LenderTrancheAxis=gnrt_ExcludingCommercialTrancheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_LenderTrancheAxis=gnrt_KSureTrancheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_LenderTrancheAxis=gnrt_KeximFundedTrancheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_LenderTrancheAxis=gnrt_KeximGuaranteedTrancheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_VesselByTypeAxis=gnrt_VeryLargeCrudeCarriersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_BasisOfBorrowingAxis=gnrt_FinalContractPriceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_BasisOfBorrowingAxis=gnrt_MaximumContractPriceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_BasisOfBorrowingAxis=gnrt_FairMarketValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_VesselByTypeAxis=gnrt_VlccVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	dei_LegalEntityAxis=gnrt_Gener8MaritimeSubViiiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LONG-TERM DEBT - Korean Export Credit Facility (Details) $ in Millions	Sep. 26, 2017 USD ($)	Jun. 01, 2017	Sep. 03, 2015 USD ($) item	Dec. 31, 2017 item
Gener8 Nestor
Long-term debt
Amount of reduction in the contract price payable	$ 19.3
Damages due to late delivery of Vessel	5.4
Original contract price of the vessel	96.4
Amended contract price of vessel	77.1
Original final installment due	48.3
Amended final installment due	$ 29.0
Korean Export Credit Facility
Long-term debt
Minimum liquidity based on amount outstanding in the Company’s debt service reserve account (as a percent)		50.00%
Korean Export Credit Facility \| Term Loan
Long-term debt
Maximum borrowing capacity			$ 963.7
Additional accrual rate if failure to pay any amount due			2.00%
Korean Export Credit Facility \| Commercial Tranche \| Term Loan
Long-term debt
Maximum borrowing capacity			$ 282.0
Loan maturity			60 months
Korean Export Credit Facility \| Excluding Commercial Tranche \| Term Loan
Long-term debt
Loan maturity			144 months
Korean Export Credit Facility \| K-Sure Tranche \| Term Loan
Long-term debt
Maximum borrowing capacity			$ 344.6
Korean Export Credit Facility \| KEXIM Funded Tranche \| Term Loan
Long-term debt
Maximum borrowing capacity			197.4
Korean Export Credit Facility \| KEXIM Guaranteed Tranche \| Term Loan
Long-term debt
Maximum borrowing capacity			$ 139.7
Korean Export Credit Facility \| VLCCs
Long-term debt
New building vessels \| item			15
Korean Export Credit Facility \| VLCCs \| Final Contract Price
Long-term debt
Amount borrowed as a percentage of vessel price or fair market value			65.00%
Korean Export Credit Facility \| VLCCs \| Maximum Contract Price
Long-term debt
Amount borrowed as a percentage of vessel price or fair market value			65.00%
Korean Export Credit Facility \| VLCCs \| Fair Market Value
Long-term debt
Amount borrowed as a percentage of vessel price or fair market value			60.00%
Korean Export Credit Facility \| VLCC vessels
Long-term debt
Number of pledged vessels \| item				13
Korean Export Credit Facility \| LIBOR \| Commercial Tranche \| Term Loan
Long-term debt
Margin on variable interest rate			2.75%
Korean Export Credit Facility \| LIBOR \| K-Sure Tranche \| Term Loan
Long-term debt
Margin on variable interest rate			1.70%
Korean Export Credit Facility \| LIBOR \| KEXIM Funded Tranche \| Term Loan
Long-term debt
Margin on variable interest rate			2.60%
Korean Export Credit Facility \| LIBOR \| KEXIM Guaranteed Tranche \| Term Loan
Long-term debt
Margin on variable interest rate			1.50%
Gener8 Maritime Sub VIII \| Korean Export Credit Facility \| Commercial Tranche \| Term Loan
Long-term debt
Number of payment installments \| item			20
Frequency of payment installments			quarterly
Balloon payment to loan ratio			66.70%
Gener8 Maritime Sub VIII \| Korean Export Credit Facility \| Excluding Commercial Tranche \| Term Loan
Long-term debt
Number of payment installments \| item			48