Summary of Significant Accounting Policies (Narrative) (Details) (USD $) In Thousands, except Share data in Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Restricted cash	$ 37		$ 37
Property, Plant and Equipment [Line Items]
Property and equipment, net	659us-gaap_PropertyPlantAndEquipmentNet		279us-gaap_PropertyPlantAndEquipmentNet
Depreciation expense	11us-gaap_Depreciation	2us-gaap_Depreciation
Prepaid clinical expenses	1,449ljpc_PrepaidClinicalExpense		1,528ljpc_PrepaidClinicalExpense
Potentially dilutive common shares related to the outstanding preferred stock, stock options, restricted stock units and warrants	8.8	10.2
Comprehensive loss	$ (8,955)	$ (5,128)
Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of the assets	2 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of the assets	7 years

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- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

+ References

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- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

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.

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