MERGER WITH VALLON - Narrative (Details)	Apr. 21, 2023 $ / shares shares	Apr. 20, 2023
Business Acquisition [Line Items]
Ownership percentage in common stock (as a percent)		15.00%
Issuance of common stock for reverse recapitalization expenses (in shares)	19
GRI Operations
Business Acquisition [Line Items]
Common stock, exchange ratio	0.0374
Ownership percentage in common stock (as a percent)		85.00%
Exchange Warrants
Business Acquisition [Line Items]
Number of shares called by warrants (in shares)	272
Warrant exercise price (in usd per share) \| $ / shares	$ 22,787.31

Common Stock Exchange Ratio

No definition available.

Name:	gribio_CommonStockExchangeRatio
Namespace Prefix:	gribio_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Common Stock, Ownership Percentage

+ References

No definition available.

+ Details

Name:	gribio_CommonStockOwnershipPercentage
Namespace Prefix:	gribio_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Stock Issued During Period, Shares, Reverse Recapitalization Expenses

+ References

No definition available.

+ Details

Name:	gribio_StockIssuedDuringPeriodSharesReverseRecapitalizationExpenses
Namespace Prefix:	gribio_
Data Type:	xbrli:sharesItemType
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-5

+ Details

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

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-3

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

+ Details

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=gribio_GRIOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=gribio_ExchangeWarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: