Fair Value Measurements (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	Jul. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Symphony Base Payment in Shares	13,237,519lxrx_SymphonyBasePaymentInShares
Symphony Base Payment Obligation	$ 35lxrx_SymphonyBasePaymentObligation

On July 30, 2010, Lexicon entered into an Amended and Restated Purchase Option Agreement with Symphony Icon and Holdings and simultaneously exercised the Purchase Option, thereby reacquiring the Programs. Pursuant to the amended terms of the Purchase Option, Lexicon paid Holdings $10 million and issued 13,237,519 shares of common stock to designees of Holdings on July 30, 2012 in satisfaction of an additional $35 million base payment obligation. Lexicon also agreed to make up to $45 million in additional payments, which will consist of 50% of any consideration Lexicon receives pursuant to any licensing transaction under which Lexicon grants a third party rights to commercialize LX1032, LX1033 or other pharmaceutical compositions modulating the same target as those drug candidates. This represents the 13,237,519 shares of common stock issued to designees of Holdings on July 30, 2012 in satisfaction of the base payment obligation.

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