Summary of Significant Accounting Policies Concentration of Credit Risk (Details)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Concentration Risk
Disclosure On Geographic Areas Revenue From External Customers Attributed to France	94.00%
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Entity's Country of Domicile, Percent	6.00%	100.00%	100.00%

Revenues from external customers attributed to the entity's country of domicile as a percentage of total revenue.

No definition available.

Name:	lxrx_DisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToEntitysCountryOfDomicilePercent
Namespace Prefix:	lxrx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration