Impairment of right-of-use asset during the period.

No definition available.

Name:	gnk_ImpairmentOfRightOfUseAsset
Namespace Prefix:	gnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Free base rental period upon commencement of the sublease.

+ References

No definition available.

+ Details

Name:	gnk_LeaseFreeBaseRentalSubleasePeriod
Namespace Prefix:	gnk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of monthly base sublease income

+ References

No definition available.

+ Details

Name:	gnk_MonthlyBaseSubleaseIncome
Namespace Prefix:	gnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the monthly payments that the lessee is obligated to make or can be required to make in connection with a property under the terms of an agreement classified as an operating lease.

+ References

No definition available.

+ Details

Name:	gnk_OperatingLeasesMonthlyRentPayment
Namespace Prefix:	gnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the obligation of sublessor towards the cost of alterations to the assets under the lease agreement.

+ References

No definition available.

+ Details

Name:	gnk_OperatingLeasesObligationOfSublessorTowardsCostOfAlterationsOfAssetUnderLease
Namespace Prefix:	gnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of lease cost recognized by lessee for lease contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=77888399&loc=SL77918982-209971

+ Details

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

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

+ Details

Name:	us-gaap_LesseeOperatingLeaseTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Amount of sublease income excluding finance and operating lease expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=77888399&loc=SL77918982-209971

+ Details

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

- Details

Name:	gnk_OperatingLeaseRentExpensePeriodAxis=gnk_OperatingLeasePeriodFrom26July2019To29September2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_OperatingLeaseRentExpensePeriodAxis=gnk_OperatingLeasePeriodFrom10December2019To29September2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=gnk_LeaseAgreementForOfficeSpaceEnteredApril2011Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_OperatingLeaseRentExpensePeriodAxis=gnk_OperatingLeaseRentExpensePeriodFrom1October2018To30April2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_OperatingLeaseRentExpensePeriodAxis=gnk_OperatingLeaseRentExpensePeriodFrom1May2023To30September2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=gnk_SubSubleaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_OperatingLeaseRentExpensePeriodAxis=gnk_OperatingLeaseRentExpensePeriodUntil31May2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_OperatingLeaseRentExpensePeriodAxis=gnk_OperatingLeaseRentExpensePeriodAfter31May2015UntilEndOfLeaseTermMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=gnk_LeaseAgreementOfficeSpace2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_SG
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LEASES - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended
LEASES - Narrative (Details) - USD ($) $ in Thousands	Jun. 14, 2019	Apr. 04, 2011	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jan. 17, 2019
Leases
Impairment of right-of-use asset				$ 223
Sublease income			$ 306		$ 0
Total lease cost			483		$ 452
Period from July 26, 2019 to September 29, 2025
Leases
Free base rental period of the sublease	4 months 15 days
Period from December 10, 2019 to September 29, 2025
Leases
Monthly base sublease income	$ 102
Lease agreement entered into April 2011
Leases
Lease term		7 years
Obligation of sublessor towards the cost of alterations of office space		$ 472
Lease agreement entered into April 2011 \| Period from October 1, 2018 to April 30, 2023
Leases
Monthly rental payment			186
Lease agreement entered into April 2011 \| Period from May 1, 2023 to September 30, 2025
Leases
Monthly rental payment			$ 204
Sub Sublease Agreement \| Period November 1, 2011 until May 31, 2015
Leases
Monthly rental payment		82
Sub Sublease Agreement \| Period after May 31, 2015 until April 30, 2018
Leases
Monthly rental payment		$ 90
Lease Agreement entered into January 2019 \| Singapore
Leases
Lease term						3 years