Statements of Comprehensive Loss Parenthetical (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Stock-based compensation expense associated with research and development expense	$ 1,330	$ 1,037
Stock-based compensation expense associated with general and administrative expense	$ 779	$ 681

Stock-based compensation expense associated with general and administrative expense.

No definition available.

Name:	lxrx_StockBasedCompensationExpenseAssociatedWithGeneralAndAdministrativeExpense
Namespace Prefix:	lxrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration