Summary of Significant Accounting Policies Concentration of Credit Risk (Details)	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Concentration Risk
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Entity's Country of Domicile, Percent	100.00%	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