The amount of consecutive quarterly commitment reduction at the end of the reporting period.

No definition available.

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

- Definition

Threshold borrowing limit under the line of credit facility at the end of the of the reporting period.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of vessels committed to be acquired by the entity under purchase agreement.

+ References

No definition available.

+ Details

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

- Definition

Threshold percentage of ratio of outstanding loan to the aggregate appraised value of collateral vessels.

+ References

No definition available.

+ Details

Name:	gnk_ThresholdPercentageOfRatioOfOutstandingLoanToAggregateAppraisedValueOfCollateralVessels
Namespace Prefix:	gnk_
Data Type:	num:percentItemType
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

Period remaining on line of credit facility before it terminates, 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_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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://fasb.org/us-gaap/role/ref/legacyRef
-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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Definition

The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnk_CreditAgricoleCorporateAndInvestmentBankSeniorSecuredCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=gnk_AgreementToPurchaseUltrabulkAndCapesizeVesselsJune2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnk_OneHundredAndThirtyThreeMillionDollarsCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gnk_RevolvingCreditFacilityUnderOneHundredAndThirtyThreeMillionCreditFacilityMember
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:

DEBT - $133 Million Credit Facility (Details) - Secured Debt				3 Months Ended		6 Months Ended
	Jun. 15, 2020 USD ($)	Jun. 11, 2020 USD ($)	Aug. 14, 2018 USD ($) item	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
$108 Million Credit Facility
Line of Credit Facility
Maximum borrowing capacity			$ 108,000,000
Term of facilities			5 years
$108 Million Credit Facility \| Agreement To Purchase Ultramax And Capesize Vessels
Line of Credit Facility
Number of vessels committed to be acquired under purchase agreement \| item			6
$133 Million Credit Facility
Line of Credit Facility
Maximum borrowing capacity				$ 133,000,000		$ 133,000,000
Drawdowns during the period						24,000,000
Remaining borrowing capacity				1,000,000		1,000,000
Repayment of secured debt				$ 1,700,000	$ 1,580,000	$ 3,280,000	$ 3,160,000
Revolver
Line of Credit Facility
Maximum borrowing capacity		$ 25,000,000
Minimum amounts of borrowings		1,000
Consecutive quarterly commitment reductions		$ 1,900,000
Threshold percentage of ratio of outstanding loan to aggregate appraised value of collateral vessels.		60.00%
Drawdowns during the period	$ 24,000,000
Revolver \| LIBOR
Line of Credit Facility
Applicable margin over reference rate for interest payable		3.00%