Leases - lessor (Details) $ in Thousands	3 Months Ended
Feb. 29, 2020 USD ($) ft²
Future minimum rental payments to be received under noncancelable leases
Balance of fisal 2020	$ 25,630
2021	32,113
2022	24,789
2023	19,615
2024	16,618
Later years	39,383
Total	$ 158,148
1985 Blue Hills
Lessor operating leases
Area Of Building \| ft²	165,000
Purchase price	$ 11,500

The area of the building.

No definition available.

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- Definition

Purchase price lessee to acquire underlying asset related to operating lease.

+ References

No definition available.

+ Details

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Namespace Prefix:	grif_
Data Type:	xbrli:monetaryItemType
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- References

No definition available.

+ Details

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- Definition

Amount of lease payments to be received by lessor for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=119202524&loc=SL77919396-209981

+ Details

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- Definition

Amount of lease payments to be received by lessor in fifth fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest statement of financial position date.

+ References

+ Details

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- Definition

Amount of lease payments to be received by lessor in fourth year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.

+ References

+ Details

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- Definition

Amount of lease payments to be received by lessor in remainder of fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=119202524&loc=SL77919396-209981

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of lease payments to be received by lessor after fifth fiscal year following latest statement of financial position date for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.

+ References

+ Details

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- Definition

Amount of lease payments to be received by lessor in third fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.

+ References

+ Details

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- Definition

Amount of lease payments to be received by lessor in second fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.

+ References

+ Details

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- References

No definition available.

+ Details

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- Details

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