GENERAL INFORMATION (Details) $ in Thousands	9 Months Ended
Sep. 30, 2021 USD ($) item t segment
Segment reporting
Number of reportable segments \| segment	1
Drybulk Vessels
Segment reporting
Number of vessels in fleet	43
Capacity of vessels \| t	4,568,600
Average age of vessels	10 years 2 months 12 days
Capesize Drybulk Carriers
Segment reporting
Number of vessels in fleet	17
Ultramax Vessels
Segment reporting
Number of vessels in fleet	13
Supramax Vessels
Segment reporting
Number of vessels in fleet	13
GSSM \| Variable Interest Entity
Segment reporting
Ownership percentage	50.00%
Payments to acquire ownership interest \| $	$ 50
GSSM \| Synergy
Segment reporting
Ownership by synergy	50.00%
Payments to acquire ownership interest \| $	$ 50

Average age of vessels.

No definition available.

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Namespace Prefix:	gnk_
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Balance Type:	na
Period Type:	duration

- Definition

Represents the capacity of vessels expressed in deadweight tonnage (dwt), a measure of weight a ship is carrying or can safely carry.

+ References

No definition available.

+ Details

Name:	gnk_CapacityOfVesselsInDeadweightTonnage
Namespace Prefix:	gnk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of vessels in the fleet.

+ References

No definition available.

+ Details

Name:	gnk_NumberOfVesselsInFleet
Namespace Prefix:	gnk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Variable interest entity ownership percentage held by third party.

+ References

No definition available.

+ Details

Name:	gnk_VariableInterestEntityOwnershipPercentageHeldByThirdParty
Namespace Prefix:	gnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121559654&loc=SL6759159-111685

+ Details

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

- Details

Name:	gnk_VesselByTypeAxis=gnk_DrybulkVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_VesselByTypeAxis=gnk_CapesizeDrybulkVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_VesselByTypeAxis=gnk_UltramaxDrybulkVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gnk_VesselByTypeAxis=gnk_SupramaxDrybulkVesselsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=gnk_GsShipmanagementPte.LtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix:
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Balance Type:
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- Details

Name:	dei_LegalEntityAxis=gnk_SynergyMarinePte.LtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: