Income Taxes - Components of Deferred Tax Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Net operating loss carryforwards	$ 33,267	$ 21,085
Research and development credit carryforwards	1,979	1,511
Accruals and other	948	333
Capitalized license and organization costs	73ebio_DeferredTaxAssetsLicenses	79ebio_DeferredTaxAssetsLicenses
Capitalized start-up costs	309	340
Total gross deferred tax asset	36,576us-gaap_DeferredTaxAssetsGross	23,348us-gaap_DeferredTaxAssetsGross
Deferred tax liability	(18)us-gaap_DeferredIncomeTaxLiabilities	(77)us-gaap_DeferredIncomeTaxLiabilities
Valuation allowance	(36,558)	(23,271)
Net deferred tax asset	$ 0us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 0us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred Tax Assets Capitalized Start Up Costs

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- Definition

Deferred Tax Assets Licenses

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from in-process research and development costs expensed in connection with a business combination.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from other reserves and accruals not separately disclosed.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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