Represents the consolidated debt leverage ratio under the debt instrument.

No definition available.

Name:	gnrt_DebtLeverageRatio
Namespace Prefix:	gnrt_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of final installment paid for the vessel.

+ References

No definition available.

+ Details

Name:	gnrt_PaymentOfFinalInstallmentOfVessel
Namespace Prefix:	gnrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

+ 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 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

+ Details

Name:	us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfSeniorDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

- Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_VesselsByNameAxis=gnrt_Gener8ArgusMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnrt_VesselsByNameAxis=gnrt_Gener8ZeusMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis=gnrt_Gener8PericlesMember
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:	gnrt_VesselsByNameAxis=gnrt_Gener8NestorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

SUBSEQUENT EVENTS (Details) $ in Thousands						9 Months Ended
SUBSEQUENT EVENTS (Details) $ in Thousands	Nov. 08, 2017	Nov. 07, 2017 USD ($)	Oct. 30, 2017 USD ($)	Oct. 18, 2017 USD ($)	Oct. 09, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Subsequent events
Borrowings under credit facilities						$ 100,131	$ 636,216
Outstanding payable balance						$ 26,907		$ 33,991
Sinosure Credit Facility
Subsequent events
Consolidated leverage ratio		0.65
Subsequent events. \| Gener8 Argus
Subsequent events
Gross proceeds from sale of vessel			$ 11,000
Subsequent events. \| Gener8 Zeus
Subsequent events
Gross proceeds from sale of vessel		$ 53,000
Subsequent events. \| Gener8 Pericles
Subsequent events
Gross proceeds from sale of vessel				$ 11,000
Subsequent events. \| Korean Export Credit Facility \| Gener8 Nestor
Subsequent events
Borrowings under credit facilities					$ 48,000
Payment of final installment					29,000
Outstanding payable balance					$ 0
Subsequent events. \| Refinancing Facility \| Gener8 Argus
Subsequent events
Repayments of senior debt			$ 7,700
Subsequent events. \| Refinancing Facility \| Gener8 Zeus
Subsequent events
Repayments of senior debt		$ 34,300
Subsequent events. \| Refinancing Facility \| Gener8 Pericles
Subsequent events
Repayments of senior debt				$ 7,800
Subsequent events. \| Sinosure Credit Facility
Subsequent events
Consolidated leverage ratio	0.60