Supplemental Financial Statement Information - AFS Securities (Details)	12 Months Ended
Nov. 30, 2017 shares
Investments
Shares of Centaur Media common stock sold	1,952,462

Represents the number of shares of common stock sold.

No definition available.

Name:	grif_InvestmentOwnedSharesSold
Namespace Prefix:	grif_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration