SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue and Voyage Expense (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($)	Dec. 31, 2018 item
Voyage expense recognition
Net (loss) gain on purchase and sale of bunker fuel and net realizable value adjustments	$ 113	$ 1,034	$ (237)	$ 1,889
Charter hire expenses	$ 4,849	$ 509	$ 7,267	$ 509
Number of vessels in vessel pools \| item	0		0		0

Represents the net gains (losses) resulting from the difference between the cost of bunker fuel delivered by the terminating charterer and the bunker fuel sold to the new charterer and the lower of cost and net realizable value adjustment to re-value bunker fuel on a quarterly basis.

No definition available.

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