RETIREMENT BENEFIT OBLIGATION (Details 2) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Statement1 [Line Items]
Present value of unfunded obligations	$ 1,613	$ 1,819
Present value of obligations in excess of plan assets	$ 1,613	$ 1,819

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling.

No definition available.

Name:	grin_PresentValueOfObligationsInExcessOfPlanAssets
Namespace Prefix:	grin_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant