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Namespace Prefix:	crsp_
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Balance Type:	na
Period Type:	duration

- Definition

Number of additional renewal terms.

+ References

No definition available.

+ Details

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Namespace Prefix:	crsp_
Data Type:	xbrli:integerItemType
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Period Type:	duration

- Definition

Rental payments period under lease arrangement.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
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- 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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Data Type:	xbrli:stringItemType
Balance Type:	na
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- 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=121609121&loc=SL77918673-209980

+ Details

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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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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=121609121&loc=SL77918673-209980

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

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

+ References

+ 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 operating sublease.

+ References

+ Details

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

- Details

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Namespace Prefix:
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- Details

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- Details

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- Details

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- Details

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- Details

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Leases - Additional Information (Detail) $ in Millions	1 Months Ended							12 Months Ended
Leases - Additional Information (Detail) $ in Millions	Jul. 31, 2020 USD ($)	May 31, 2020 Term	Dec. 31, 2019	Nov. 30, 2019 USD ($)	May 31, 2019	May 31, 2016	Jun. 30, 2015	Dec. 31, 2020
2015 Lease [Member]
Lessee Lease Description [Line Items]
Lease commencement date							Nov. 15, 2015
Lessee, operating lease, existence of option to extend							false
Lessee, operating lease, option to extend								expires in September 2022 with no further option to extend
Lease expiration, month and year							2022-09
2016 Sublease [Member]
Lessee Lease Description [Line Items]
Lease commencement date						Dec. 23, 2016
Lease expiration, month and year						2026-12
Lessee, operating sublease, option to extend								an option to extend the term of the 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
Lessee, operating lease, existence of option to extend					true
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.
Lease expiration, month and year					2026-11
Extended term of lease expiration					5 years
2019 Sublease [Member]
Lessee Lease Description [Line Items]
Lease expiration, month and year			2024-03
Lessee, operating sublease, option to extend								an option to extend the term of the 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
Framingham Lease [Member]
Lessee Lease Description [Line Items]
Lease expiration, month and year		2036-03
Lessee, operating sublease, existence of option to extend		true
Number of additional renewal terms \| Term		2
Lease renewal term under each extension option		7 years
2020 Boston Lease [Member]
Lessee Lease Description [Line Items]
Annual rental payments	$ 292.5
Rental payments period	152 months
Lease Arrangement
Lessee Lease Description [Line Items]
Annual rental payments				$ 3.8
Rental payments period				5 years