Represents daily gross rate per vessel in vessel pool.

No definition available.

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

- Definition

Represents the number of vessels directly admitted into pool by the entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage of revenue share on earnings above daily threshold from related party transactions.

+ References

No definition available.

+ Details

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

- Definition

The number of vessels for which notices were delivered for the termination of pool agreement.

+ References

No definition available.

+ Details

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

- Definition

Represents the threshold of daily gross rate per vessel in vessel pool subject to percentage of profit share.

+ References

No definition available.

+ Details

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

- Definition

For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
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-Section 50
-Paragraph 1
-Subparagraph (d)
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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.9-03.10(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DueFromRelatedParties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

+ Details

Name:	us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 32
-Paragraph 2A
-URI http://asc.fasb.org/extlink&oid=82859839&loc=SL82860478-203043

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+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gnrt_Navig8GroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=gnrt_Vl8PoolMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=gnrt_Suez8PoolMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=gnrt_V8PoolMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gnrt_Vl8PoolIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gnrt_Navig8IncMember
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:	gnrt_VesselByTypeAxis=gnrt_SuezmaxVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=gnrt_V8PoolInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=gnrt_Navig8PoolAffiliateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

RELATED PARTY TRANSACTIONS - Navig8 Pools (Details) $ in Thousands	3 Months Ended		11 Months Ended
	Mar. 31, 2018 USD ($) item	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)
Navig8 Group
Related party transactions
Due from related parties	$ 25,600			$ 26,300
Navig8 Group \| VL8 Pool
Related party transactions
Due from related parties	19,000			18,800
Navig8 Group \| Suez8 Pool
Related party transactions
Due from related parties	5,900			6,400
Navig8 Group \| V8 Pool
Related party transactions
Due from related parties	$ 700			$ 1,100
VL8 Pool Inc. \| VL8 Pool
Related party transactions
Number of vessels advising of the termination of pool agreements \| item	26
Nave Quasar \| Navig8 Inc.
Related party transactions
Gross daily rate			$ 26
Revenue share above daily threshold (as a percent)			50.00%
Threshold gross daily rate			$ 30
Amount of expense incurred on behalf of related parties		$ 6
VLCC vessels \| VL8 Pool Inc. \| VL8 Pool
Related party transactions
Number of vessels directly admitted to pool \| item	21
Suezmax Vessels \| V8 Pool Inc. \| Suez8 Pool
Related party transactions
Number of vessels directly admitted to pool \| item	6
Navig8 Pool \| Navig8 Group
Related party transactions
Shipping Revenues	$ 43,200	118,400
Navig8 Pool \| Navig8 Group \| VL8 Pool
Related party transactions
Shipping Revenues	37,400	90,500
Navig8 Pool \| Navig8 Group \| Suez8 Pool
Related party transactions
Shipping Revenues	$ 5,800	22,300
Navig8 Pool \| Navig8 Group \| V8 Pool
Related party transactions
Shipping Revenues		$ 5,600