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 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 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=75038535&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:	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) - Korean Export Credit Facility - Term Loan $ in Millions	Sep. 03, 2015 USD ($) item	Mar. 31, 2018 item
Long-term debt
Maximum borrowing capacity	$ 963.7
Additional accrual rate if failure to pay any amount due	2.00%
Commercial Tranche
Long-term debt
Maximum borrowing capacity	$ 282.0
Loan maturity	60 months
Excluding Commercial Tranche
Long-term debt
Loan maturity	144 months
K-Sure Tranche
Long-term debt
Maximum borrowing capacity	$ 344.6
KEXIM Funded Tranche
Long-term debt
Maximum borrowing capacity	197.4
KEXIM Guaranteed Tranche
Long-term debt
Maximum borrowing capacity	$ 139.7
VLCCs
Long-term debt
New building vessels \| item	15
VLCCs \| Final Contract Price
Long-term debt
Amount borrowed as a percentage of vessel price or fair market value	65.00%
VLCCs \| Maximum Contract Price
Long-term debt
Amount borrowed as a percentage of vessel price or fair market value	65.00%
VLCCs \| Fair Market Value
Long-term debt
Amount borrowed as a percentage of vessel price or fair market value	60.00%
VLCC vessels
Long-term debt
Number of pledged vessels \| item		13
LIBOR \| Commercial Tranche
Long-term debt
Margin on variable interest rate	2.75%
LIBOR \| K-Sure Tranche
Long-term debt
Margin on variable interest rate	1.70%
LIBOR \| KEXIM Funded Tranche
Long-term debt
Margin on variable interest rate	2.60%
LIBOR \| KEXIM Guaranteed Tranche
Long-term debt
Margin on variable interest rate	1.50%
Gener8 Maritime Sub VIII \| Commercial Tranche
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 \| Excluding Commercial Tranche
Long-term debt
Number of payment installments \| item	48