Area of real estate that have been pledged as collateral for borrowings.

No definition available.

Name:	grif_AreaOfRealEstatePledgedAsCollateral
Namespace Prefix:	grif_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The period for which the maturity date of the debt instrument was extended.

+ References

No definition available.

+ Details

Name:	grif_DebtInstrumentPeriodOfExtensionOfMaturityDate
Namespace Prefix:	grif_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum period with in which the entity has to get performance financing from the date of withdrawn from acquisition credit line.

+ References

No definition available.

+ Details

Name:	grif_MaximumPeriodForObtainingPermanentFinancingFromDrawnOfFundsFromAcquisitionCreditLine
Namespace Prefix:	grif_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_ProceedsFromLinesOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=grif_GriffinCenterSouthBloomfieldCTMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=grif_GriffinCenterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=grif_AcquisitionCreditLineFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=grif_IndustrialOrWarehouseBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Revolving Credit Agreement (Details) $ in Thousands			3 Months Ended	6 Months Ended	72 Months Ended
Revolving Credit Agreement (Details) $ in Thousands	Jun. 25, 2019 USD ($) ft²	Mar. 29, 2018	Feb. 28, 2019 USD ($)	May 31, 2019 USD ($) ft²	Nov. 30, 2018 USD ($)
Revolving credit agreement
Term of debt		15 years
Webster Credit Line
Revolving credit agreement
Maximum borrowing capacity				$ 15,000
Present borrowing capacity	$ 19,500
Term of debt	2 years
Extension period	1 year
Proceeds from Lines of Credit			$ 0		$ 0
Standby letters of credit aggregate amount				$ 639
Webster Credit Line \| Griffin Center South, Bloomfield, CT
Revolving credit agreement
Area of collateralized properties (in square feet) \| ft²				235,000
Webster Credit Line \| Single-story office building in Griffin Center
Revolving credit agreement
Area of collateralized properties (in square feet) \| ft²				48,000
Webster Credit Line \| LIBOR
Revolving credit agreement
Variable interest rate margin (as a percent)				2.75%
Acquisition Credit Line
Revolving credit agreement
Maximum borrowing capacity	$ 15,000
Maximum period for obtaining permanent finance from date of drawn	135 days
Term of debt	2 years
Extension period	1 year
Acquisition Credit Line \| Industrial/warehouse building
Revolving credit agreement
Area of collateralized properties (in square feet) \| ft²	31,000