Lease commencement date.

No definition available.

Name:	crsp_LeaseCommencementDate
Namespace Prefix:	crsp_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_LeaseExpirationDate1
Namespace Prefix:	us-gaap_
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

Name:	us-gaap_LesseeLeaseDescriptionLineItems
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=77888426&loc=SL77918673-209980

+ Details

Name:	us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend
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

Name:	us-gaap_LesseeOperatingLeaseOptionToExtend
Namespace Prefix:	us-gaap_
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=77888426&loc=SL77918673-209980

+ Details

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

- Definition

Indicates (true false) whether sublessee has option to extend operating sublease.

+ References

+ Details

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

- Definition

Description of terms and conditions of option to extend operating sublease.

+ References

+ Details

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

- Details

Name:	us-gaap_TypeOfArrangementAxis=crsp_TwoThousandAndFifteenLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=crsp_TwoThousandAndSixteenSubleaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=crsp_TwoThousandAndNineteenLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Leases - Additional Information (Detail)	1 Months Ended			9 Months Ended
Leases - Additional Information (Detail)	May 31, 2019	May 31, 2016	Jun. 30, 2015	Sep. 30, 2019
2015 Lease [Member]
Lessee Lease Description [Line Items]
Lease commencement date			Nov. 15, 2015
Lease expiration date			Feb. 28, 2022
2016 Sublease [Member]
Lessee Lease Description [Line Items]
Lease commencement date		Dec. 23, 2016
Lease expiration date		Dec. 31, 2026
Lessee, operating sublease, option to extend				an option to extend the term of sublease for an additional five-year period if, at the time of expiration of the initial term
Lessee, operating sublease, existence of option to extend		true
Extended term of lease expiration		5 years
2019 Lease [Member]
Lessee Lease Description [Line Items]
Lease commencement date	Jun. 01, 2019
Lease expiration date	Nov. 30, 2026
Extended term of lease expiration	5 years
Lessee, operating lease, option to extend				an option to extend the term of the lease for an additional five-year period based on certain conditions within the Company’s control.
Lessee, operating lease, existence of option to extend	true