FINANCIAL INSTRUMENTS, FINANCIAL RISKS AND CAPITAL MANAGEMENT (Details 3) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
United States dollars [Member]
Statement1 [Line Items]
Impact on profit or loss in foreign currency strengthen by 10 %	$ 54	$ 160
South africa rands [Member]
Statement1 [Line Items]
Impact on profit or loss in foreign currency strengthen by 10 %	$ (488)	$ (40)

The amount of exchange differences recognised in profit or loss that arise from foreign currency transactions strengthens by 10 %.

No definition available.

Name:	grin_ImpactOnProfitOrLossInForeignCurrencyStrengthenBy10Percentage
Namespace Prefix:	grin_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration