Finance lease maturity date.

No definition available.

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Namespace Prefix:	grph_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Fixed lease payments.

+ References

No definition available.

+ Details

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Namespace Prefix:	grph_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Lessee operating lease weighted average incremental borrowing rate.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of office suites.

+ References

No definition available.

+ Details

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Namespace Prefix:	grph_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Operating lease base rent.

+ References

No definition available.

+ Details

Name:	grph_OperatingLeaseBaseRent
Namespace Prefix:	grph_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Operating lease commencement date.

+ References

No definition available.

+ Details

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Namespace Prefix:	grph_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Operating lease maturity date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date which lease or group of leases is set to expire, in YYYY-MM-DD format.

+ References

No definition available.

+ Details

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Data Type:	xbrli:dateItemType
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

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

- Definition

Indicates (true false) whether lessee has option to extend operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918673-209980

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of terms and conditions of option to extend lessee's operating lease. Includes, but is not limited to, information about option recognized as part of right-of-use asset and lease liability.

+ References

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918673-209980

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of operating lease expense. Excludes sublease income.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918638-209977

+ Details

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

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

+ Details

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

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

+ References

+ Details

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

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

+ References

+ Details

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

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
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-SubTopic 20
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-Paragraph 4
-Subparagraph (g)(3)
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (d)
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+ Details

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

- Details

Name:	us-gaap_TypeOfArrangementAxis=grph_LeaseAgreementMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=grph_FirstOfficeSuiteLeaseAgreementMember
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Balance Type:
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- Details

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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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- Details

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Operating Leases - Additional Information (Details) $ in Thousands					1 Months Ended		12 Months Ended
	Nov. 17, 2021 USD ($)	Nov. 10, 2021	May 10, 2021 USD ($)	Jan. 27, 2021 OfficeSuite	Mar. 31, 2021	Apr. 30, 2020	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Lessee Lease Description [Line Items]
Term of contract						1 year
Operating lease commencement date						May 11, 2020
Operating lease maturity date					Sep. 30, 2021	Jun. 30, 2021
Lessee, operating lease, option to extend							The original term of the lease was from May 11, 2020 to June 30, 2021 with an option to renew. In March 2021, the Company entered into an amendment to the lease agreement and extended the term of the lease to September 30, 2021.
Lessee, Operating Lease, Existence of Option to Extend [true false]						true
Operating lease base rent							$ 0	$ 200
Operating lease right-of-use assets							11,574
Operating lease liability							11,276
Current portions of operating lease liability							5,482
Non-current portions of operating lease liability							$ 5,794
Remaining lease term on operating lease							27 months
Weighted average incremental borrowing rate on operating lease							8.40%
Lease expense							$ 1,900	$ 300
Variable lease payments							$ 200
Lease Agreement
Lessee Lease Description [Line Items]
Lessee, operating lease, option to extend							The term of the lease is 44 months for the first office suite and 43 months for the second office suite with an option to extend the term for an additional two years on the same terms and conditions.
Lessee, Operating Lease, Existence of Option to Extend [true false]				true
Number Of Office Suites \| OfficeSuite				2
Lessee, operating lease, renewal term				2 years
Operating lease right-of-use assets							$ 6,700
Operating lease liability							$ 7,200
First Office Suite
Lessee Lease Description [Line Items]
Term of contract				44 months
Operating lease commencement date		Nov. 10, 2021		Jul. 31, 2021
Sublease expire date		Dec. 06, 2023
Second Office Suite
Lessee Lease Description [Line Items]
Term of contract				43 months
Operating lease commencement date				Aug. 31, 2021
Embedded Lease Agreement \| Laboratory For Cell And Gene Medicine
Lessee Lease Description [Line Items]
Finance lease maturity date			Apr. 30, 2023
Fixed lease payments			$ 5,600
License Service Agreement and Master Services Agreement \| Explora BioLabs, Inc
Lessee Lease Description [Line Items]
Finance lease maturity date	Nov. 30, 2023
Fixed lease payments	$ 700