Summary of Significant Accounting Policies Income Tax (Details) $ in Millions	Dec. 31, 2017 USD ($)
Summary of Significant Accounting Policies [Abstract]
Deferred Tax Asset, remeasured	$ 171.4

Deferred Tax Asset, remeasured - represents the remeasurement of the deferred tax asset and liabilities to the newly enacted US Federal corporate tax rate of 21%

No definition available.

Name:	lxrx_DeferredTaxAssetremeasured
Namespace Prefix:	lxrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant