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Number of common stock shares issuable upon achievement of milestones.

+ References

No definition available.

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- Definition

Potential future milestone payments.

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No definition available.

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- Definition

Potential milestone payments.

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No definition available.

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- Definition

Carrying amount (original costs adjusted for previously recognized amortization and impairment) as of the balance sheet date for the capitalized costs to acquire rights under a license arrangement (for example, to sell specified products in a specified territory) having an indefinite period of benefit.

+ References

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

-Publisher FASB

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-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (b)

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- Definition

Costs incurred and are directly related to generating license revenue. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2(e))

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- Definition

The minimum amount the entity agreed to spend under the long-term purchase commitment.

+ References

No definition available.

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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 1

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- 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.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 20

-Section 50

-Paragraph 1

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 730

-SubTopic 10

-Section 50

-Paragraph 1

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The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2010	Nov. 29, 2013
Commitments And Contingencies [Line Items]
Letter of credit required under operating lease included in restricted cash	$ 94,000				$ 134,000
Operating Leases Rent Expense	416,000us-gaap_OperatingLeasesRentExpenseNet	725,000us-gaap_OperatingLeasesRentExpenseNet	753,000us-gaap_OperatingLeasesRentExpenseNet
Milestone payment				4,700,000ebio_PotentialMilestonePayments
Common stock, shares issued				105,000
Up-front license payments	240,000
Research and development	26,703,000us-gaap_ResearchAndDevelopmentExpense	13,788,000us-gaap_ResearchAndDevelopmentExpense	15,263,000us-gaap_ResearchAndDevelopmentExpense
Total license expense incurred	92,000us-gaap_LicenseCosts	105,000us-gaap_LicenseCosts	127,000us-gaap_LicenseCosts
Clinical Development [Member]
Commitments And Contingencies [Line Items]
Milestone payment upon achievement of clinical milestone	350,000
Clinical Development [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Milestone payment	1,000,000
Other License Agreement [Member]
Commitments And Contingencies [Line Items]
Research and development	107,000
Upon the Achievement of Specified Regulatory Milestone Events [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Milestone payment	1,000,000
Sales Based Milestones [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Milestone payment	$ 36,000,000