Arrangements with Symphony Icon Inc (Details) (USD $)	0 Months Ended		3 Months Ended
	Apr. 24, 2015	Dec. 04, 2014	Mar. 31, 2015	Mar. 31, 2014	Jul. 30, 2012	Jul. 30, 2010	Jun. 15, 2007
Loss Contingencies [Line Items]
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 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%
Symphony Contingent Payment In Cash	750,000	5,800,000
Symphony Contingent Payment in Shares		4,662,780
Symphony Contingent Payment Total		11,500,000
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%
Increase in fair value of Symphony Icon, Inc. purchase liability			$ 1,753,000	$ 1,142,000