This item represents the change in fair value of the Symphony Icon, Inc. purchase liability. In connection with the acquisition of Symphony Icon, Lexicon made an initial estimate of the fair value of the liability for the associated based and contingent payments. Changes in this liability, based on the development of the programs and the time until such payments are expected to be made, are recorded in Lexicon's consolidated statements of operations.

No definition available.

Arrangements with Symphony Icon, Inc. (Details) (USD $)	12 Months Ended
Arrangements with Symphony Icon, Inc. (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 30, 2012	Jul. 30, 2010	Jun. 15, 2007
Loss Contingencies
Holdings Contribution To Icon						$ 45,000,000
Lexicon Sold Shares To Holdings						7,650,622
Lexicon Received Cash From Holdings						15,000,000
Lexicon Paid Holdings Cash					10,000,000
Symphony Fair Value Of Base And Contingent Payments					45,600,000
Symphony Base Payment Discount Rate					14.00%
Symphony Contingent Payment Discount Rate					18.00%
Symphony Base Payment In Shares				13,237,519
Symphony Base Payment Obligation				35,000,000
Symphony Contingent Payment Maximum					45,000,000
Symphony Contingent Payment Percentage					50.00%
Symphony Regulatory Approval Payment					15,000,000
Symphony Regulatory Approval Reduction Percentage					50.00%
Symphony Regulatory Approval Percentage Limit					50.00%
Symphony Payment In Stock Limitation					50.00%
Increase (decrease) in fair value of Symphony Icon, Inc. purchase liability	$ (2,210,000)	$ 9,887,000	$ 6,766,000