The area of land donated by the entity to another party.

No definition available.

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

- Definition

Area of land not transferred to another party through sale or donation, but retained by the entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the amortization period of the debt instrument.

+ References

No definition available.

+ Details

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

- Definition

Increase in loan amount due to refinancing arrangements.

+ References

No definition available.

+ Details

Name:	grif_DebtInstrumentIncreaseInFaceAmount
Namespace Prefix:	grif_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Area of land sold.

+ References

No definition available.

+ Details

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

- Definition

Represents the sale price of land and related assets.

+ References

No definition available.

+ Details

Name:	grif_SalePriceOfLand
Namespace Prefix:	grif_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Area of land held.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfLand
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- 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

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

Escrow deposits related to property sales in noncash investing and financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

+ Details

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

- Definition

The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=grif_NonrecourseVariableRateMortgageRefinancedDueInSeptember2026Member
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:

Subsequent Events (Details) $ in Thousands			9 Months Ended
Subsequent Events (Details) $ in Thousands	Sep. 22, 2016 USD ($) a	Sep. 13, 2016 USD ($)	Aug. 31, 2016 USD ($)	Aug. 31, 2015 USD ($)
Subsequent events
Estimated pretax gain on sale			$ 280	$ 2,163
Subsequent events
Subsequent events
Number of acres sold \| a	29
Area of Land \| a	45
Sale price	$ 3,750
Estimated pretax gain on sale	$ 3,100
Acres donated \| a	15
Acres retained \| a	1
Proceeds placed in escrow	$ 3,500
Subsequent events \| Nonrecourse Variable Rate Mortgage, Refinanced, Due In September 2026 [Member]
Subsequent events
Loan amount increase		$ 13,000
Term of debt		10 years
Amortization period of debt		25 years
Subsequent events \| Nonrecourse Variable Rate Mortgage, Refinanced, Due In September 2026 [Member] \| LIBOR
Subsequent events
Variable interest rate (as a percent)		1.70%