Deferred Underwriting Compensation - Additional Information (Details)	9 Months Ended
Sep. 30, 2018 USD ($)
Deferred Underwriting Compensation [Abstract]
Deferred underwriting compensation	$ 14,000,000
Percentage of deferred underwriting discount	3.50%
Deferred underwriting discount if business combination not completed	$ 0

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation for underwriting services related to sales of the entity's stock.

No definition available.

Name:	grsh_DeferredUnderwritingCompensationLiabilityNonCurrent
Namespace Prefix:	grsh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant