Represents the minimum cash required per vessel mortgaged under this facility.

No definition available.

Name:	gnk_LineOfCreditFacilityCovenantCashAndCashEquivalentAndRemainingBorrowingCapacityForWorkingCapitalPerVesselRequiredToBeMaintained
Namespace Prefix:	gnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the aggregate fair value of the mortgaged vessels to be maintained as a percentage of aggregate outstanding principal amount as per the terms of the credit facilities' covenants.

+ References

No definition available.

+ Details

Name:	gnk_LineOfCreditFacilityCovenantFairMarketValueOfMortgagedVesselsAsPercentageOfAggregateOutstandingPrincipalAmount
Namespace Prefix:	gnk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of fixed amortization payment for the first two years.

+ References

No definition available.

+ Details

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

- Definition

The maximum percentage of collateral required for prepayment of line of credit using excess cash flows.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of collateral vessels, in which the loan is to be prepaid from earnings received from operations after deduction of costs, fees, expenses, interest, and fixed principal repayments under the facility; operating expenses relating to the vessels; and the Borrowers’ pro rata share of general and administrative expenses based on the number of vessels they own.

+ References

No definition available.

+ Details

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Namespace Prefix:	gnk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the line of credit period without amortization, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

The amount of loan repayment requirement to have the ability to pay dividends after December 31, 2018.

+ References

No definition available.

+ Details

Name:	gnk_LoanRepaymentRequirementForAbilityToPayDividends
Namespace Prefix:	gnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the minimum cash requirement through the end of the waiver period.

+ References

No definition available.

+ Details

Name:	gnk_MinimumCashRequirementForSpecifiedPeriod
Namespace Prefix:	gnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of Entities owned or controlled by the company.

+ References

No definition available.

+ Details

Name:	gnk_NumberOfWhollyOwnedSubsidiaries
Namespace Prefix:	gnk_
Data Type:	xbrli:integerItemType
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

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentDescriptionOfVariableRateBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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://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(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 the required periodic payments of both interest and principal.

+ References

+ Details

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

- 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

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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+ Details

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

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ 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

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+ Details

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

- Definition

Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Cash and equivalents whose use in whole or in part is restricted for the long-term, generally by contractual agreements or regulatory requirements.

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
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Period Type:	instant

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DEBT - $98M Credit Facility (Details) $ in Thousands			3 Months Ended		9 Months Ended
DEBT - $98M Credit Facility (Details) $ in Thousands	Nov. 10, 2015 USD ($)	Nov. 04, 2015 USD ($) subsidiary item	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Nov. 15, 2016 USD ($)	Jun. 29, 2016 USD ($)	Jun. 28, 2016
Line of Credit Facility
Restricted cash, current			$ 8,593		$ 8,593		$ 8,242
Restricted cash, noncurrent			24,001		24,001		27,426
$98 Million Credit Facility Commitment Letter
Line of Credit Facility
Collateral security maintenance test (as a percent)									120.00%	140.00%
$98 Million Credit Facility Commitment Letter \| Minimum
Line of Credit Facility
Minimum cash requirement through the end of the waiver period									$ 25,000
Line of Credit Facility \| $98 Million Credit Facility
Line of Credit Facility
Maximum borrowing capacity		$ 98,000	98,000		98,000		98,000
Number of wholly owned subsidiaries \| subsidiary		13
Drawdowns during the period	$ 98,271
Remaining borrowing capacity			0		0
Repayment of line of credit facility			0	$ 0	0	$ 0
Long-term Debt			93,776		93,776		93,403
Collateral security maintenance test (as a percent)								140.00%
Minimum cash required to be maintained by each collateralized vessel								$ 750
Fixed amortization payment for the first two years		$ 0
Period without fixed amortization schedule		2 years
Amount of periodic payment		$ 2,500
Maximum collateral required for prepayment of loan (as a percent)		182.00%
Number of collateral vessels \| item		13
Restricted cash, current			8,593		8,593		8,242
Restricted cash, noncurrent			$ 12,506		$ 12,506		$ 15,931
Line of Credit Facility \| $98 Million Credit Facility \| LIBOR
Line of Credit Facility
Reference rate		three-month LIBOR
Applicable margin over reference rate (as a percent)		6.125%
Line of Credit Facility \| $98 Million Credit Facility \| Minimum
Line of Credit Facility
Loan repayment requirement to have the ability to pay dividends after December 31, 2018		$ 25,000
Line of Credit Facility \| $98 Million Credit Facility Commitment Letter
Line of Credit Facility
Maximum borrowing capacity									$ 98,000