The minimum amount the entity agreed to spend for research funding under the collaboration agreement.

No definition available.

Name:	juno_AggregateResearchFundingCommitmentAmount
Namespace Prefix:	juno_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Period covered by the long-term collaboration agreement research funding commitment.

+ References

No definition available.

+ Details

Name:	juno_AggregateResearchFundingCommitmentPeriod
Namespace Prefix:	juno_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Collaboration agreement aggregate success payments.

+ References

No definition available.

+ Details

Name:	juno_CollaborationAgreementAggregateSuccessPayments
Namespace Prefix:	juno_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Collaboration agreement success payments term.

+ References

No definition available.

+ Details

Name:	juno_CollaborationAgreementSuccessPaymentsTerm
Namespace Prefix:	juno_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Collaboration agreement term.

+ References

No definition available.

+ Details

Name:	juno_CollaborationAgreementTerm
Namespace Prefix:	juno_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated fair value of the total success payment liability.

+ References

No definition available.

+ Details

Name:	juno_EstimatedFairValueOfSuccessPaymentLiability
Namespace Prefix:	juno_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Multiple of equity value at issuance used in the calculation of potential success payments.

+ References

No definition available.

+ Details

Name:	juno_MultipleOfEquityValueAtIssuance
Namespace Prefix:	juno_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of clinical studies.

+ References

No definition available.

+ Details

Name:	juno_NumberOfClinicalStudies
Namespace Prefix:	juno_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Success payment liability recorded on the balance sheet.

+ References

No definition available.

+ Details

Name:	juno_SuccessPaymentLiability
Namespace Prefix:	juno_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Risk-free interest rate assumption used in valuing an instrument.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsRiskFreeInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 730

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

+ Details

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

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount per share or per unit of equity securities issued by non-development stage entity.

+ References

No definition available.

+ Details

Name:	us-gaap_SharesIssuedPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=juno_MemorialSloanKetteringCancerCenterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Collaboration Agreements - Memorial Sloan Kettering Cancer Center - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended	1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Nov. 30, 2013 Clinic
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses	$ 57,799,000us-gaap_ResearchAndDevelopmentExpense	$ 2,939,000us-gaap_ResearchAndDevelopmentExpense
Estimated fair value of total success payment obligation	230,300,000		195,900,000
Success payment liability balance	123,830,000juno_SuccessPaymentLiability		84,920,000juno_SuccessPaymentLiability
Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment	$ 60.66		52.22
Memorial Sloan Kettering Cancer Center [Member] \| Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Risk free interest rate	1.65%		1.95%
Expected term (years)	6 years 7 months 21 days		6 years 10 months 21 days
Memorial Sloan Kettering Cancer Center [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Risk free interest rate	1.91%		2.16%
Expected term (years)	9 years 7 months 24 days		9 years 10 months 21 days
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of clinical studies				6
Research and development expenses	1,000,000	300,000
Collaboration agreement, term	5 years
Estimated fair value of total success payment obligation	67,400,000		56,800,000
Success payment liability balance	35,400,000		23,700,000
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member] \| Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Term of success payments	8 years
Risk free interest rate	1.65%
Expected term (years)	6 years 7 months 21 days
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate success payments	150,000,000
Term of success payments	11 years
Risk free interest rate	1.91%
Expected term (years)	9 years 7 months 24 days
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member] \| Research and Development Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate research funding, committed				2,200,000
Aggregate research funding, commitment period				5 years
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member] \| Clinical Research and Development Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate research funding, committed				7,200,000
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member] \| Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock price per share	$ 4.00
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member] \| Common Stock [Member] \| Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Equity Value at issuance	10
Per share common stock price required for payment	$ 40.00
Collaborative Arrangement [Member] \| Memorial Sloan Kettering Cancer Center [Member] \| Common Stock [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Equity Value at issuance	30
Per share common stock price required for payment	$ 120.00