Fair Value Measurements - Additional Information (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair value of success payment obligations	$ 230,300,000	$ 195,900,000
Estimated fair value of payment liabilities portion attributable to valuation measurement date and associated elapsed service period	$ 123,830,000juno_SuccessPaymentLiability	$ 84,920,000juno_SuccessPaymentLiability

Estimated fair value of the total success payment liability.

No definition available.

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