401(k) Plan (Narrative) (Details)	9 Months Ended
Sep. 30, 2013
Compensation and Retirement Disclosure [Abstract]
401(k) Plan required eligibility service period	1 year
Percentage of employee salaries paid as contribution	3.00%

Defined Contribution Plan, Employer Discretionary Contribution Amount, Percent

No definition available.

Name:	ljpc_DefinedContributionPlanEmployerDiscretionaryContributionAmountPercent
Namespace Prefix:	ljpc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration