COMMITMENTS AND CONTINGENCIES - Operating Leases and Capital Commitments (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Commitments And Contingencies [Abstract]
Less than 1 year	$ 3,541
Between 1 and 5 years	602
More than 5 years	0
Total	$ 4,143

Operating Leases, Office Rent And Capital Commitments, Future Minimum Payments, Due In Two To Five Years

No definition available.

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Namespace Prefix:	gss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant