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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 4)
 6 Months Ended 12 Months Ended
Dec. 31, 2014
customer
item
Jul. 09, 2014
customer
item
derivative
Dec. 31, 2013
customer
item
derivative
Dec. 31, 2012
customer
Concentration Risk [Line Items]        
Percentage of revenue earned (as a percent) 100.00%gnk_ConcentrationRiskPercentageOfRevenueEarnedFromCustomers      
Number of customers 44gnk_ConcentrationRiskNumberOfCustomers      
Number of financial institutions with which the entity maintains its cash and cash equivalents 3gnk_ConcentrationRiskNumberOfFinancialInstitutionsWithWhichEntityMaintainsCashAndCashEquivalents      
Number of interest rate swaps 0us-gaap_NumberOfInterestRateDerivativesHeld      
Voyage Revenues        
Concentration Risk [Line Items]        
Major Customers 2gnk_EntityWideRevenueMajorCustomerNumber
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember		      
Concentration risk percentage (as a percent) 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember		      
Voyage Revenues | Cargill International S.A.        
Concentration Risk [Line Items]        
Concentration risk percentage (as a percent) 17.06%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_CargillInternationalSAMember		      
Voyage Revenues | Swissmarine Services S.A.        
Concentration Risk [Line Items]        
Concentration risk percentage (as a percent) 22.52%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_SwissmarineServicesSAMember		      
Predecessor        
Concentration Risk [Line Items]        
Percentage of revenue earned (as a percent)   100.00%gnk_ConcentrationRiskPercentageOfRevenueEarnedFromCustomers
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 100.00%gnk_ConcentrationRiskPercentageOfRevenueEarnedFromCustomers
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 100.00%gnk_ConcentrationRiskPercentageOfRevenueEarnedFromCustomers
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember
Number of customers   33gnk_ConcentrationRiskNumberOfCustomers
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 48gnk_ConcentrationRiskNumberOfCustomers
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 43gnk_ConcentrationRiskNumberOfCustomers
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember
Number of financial institutions with which the entity maintains its cash and cash equivalents     4gnk_ConcentrationRiskNumberOfFinancialInstitutionsWithWhichEntityMaintainsCashAndCashEquivalents
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		  
Number of interest rate swaps     4us-gaap_NumberOfInterestRateDerivativesHeld
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		  
Predecessor | Voyage Revenues        
Concentration Risk [Line Items]        
Major Customers   2gnk_EntityWideRevenueMajorCustomerNumber
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 3gnk_EntityWideRevenueMajorCustomerNumber
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 1gnk_EntityWideRevenueMajorCustomerNumber
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember
Concentration risk percentage (as a percent)   10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember
Predecessor | Voyage Revenues | Cargill International S.A.        
Concentration Risk [Line Items]        
Concentration risk percentage (as a percent)   19.37%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_CargillInternationalSAMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 21.45%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_CargillInternationalSAMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 31.27%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_CargillInternationalSAMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember
Predecessor | Voyage Revenues | Swissmarine Services S.A.        
Concentration Risk [Line Items]        
Concentration risk percentage (as a percent)   20.67%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_SwissmarineServicesSAMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		 18.73%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_SwissmarineServicesSAMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember		  
Predecessor | Voyage Revenues | Pacific Basin Chartering Ltd.        
Concentration Risk [Line Items]        
Concentration risk percentage (as a percent)     10.30%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= gnk_VoyageRevenuesMember
/ us-gaap_MajorCustomersAxis
= gnk_PacificBasinCharteringLtdMember
/ us-gaap_StatementScenarioAxis
= us-gaap_PredecessorMember