SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue and Voyage Expense (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) item	Mar. 31, 2019 USD ($)	Dec. 31, 2019 item
Voyage expense recognition
Number of vessels in vessel pools \| item	0		0
Net loss on purchase and sale of bunker fuel and net realizable value adjustments	$ 841	$ 350
Charter hire expenses	$ 3,075	$ 2,419

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