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 ($) $ in Thousands	1 Months Ended			12 Months Ended
	Sep. 30, 2016	Apr. 30, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jul. 30, 2012	Jul. 30, 2010	Jun. 15, 2007
Loss Contingencies
Holdings Contribution To Icon									$ 45,000
Lexicon Sold Shares To Holdings									1,092,946
Lexicon Received Cash From Holdings									$ 15,000
Lexicon Paid Holdings Cash								$ 10,000
Symphony Fair Value Of Base And Contingent Payments								$ 45,600
Symphony Base Payment Discount Rate								14.00%
Symphony Contingent Payment Discount Rate								18.00%
Symphony Base Payment In Shares							1,891,074
Symphony Base Payment Obligation							$ 35,000
Symphony Contingent Payment Maximum								$ 45,000
Symphony Contingent Payment Percentage								50.00%
Symphony Regulatory Approval Payment								$ 15,000
Symphony Regulatory Approval Reduction Percentage								50.00%
Symphony Regulatory Approval Percentage Limit								50.00%
Symphony Payment In Stock Limitation								50.00%
XERMELO Approval Subsequent Event Impact				$ 2,100
Symphony Contingent Payment In Cash	$ 3,200	$ 750	$ 5,800
Symphony Amendment Buyout	$ 21,000
Symphony Contingent Payment in Shares			666,111
Symphony Contingent Payment Total			$ 11,500
Increase (decrease) in fair value of Symphony Icon, Inc. purchase liability				$ (703)	$ 5,927	$ 1,428