Collaboration and License Agreements (Details) € in Millions	1 Months Ended				12 Months Ended
	Nov. 30, 2015 USD ($)	Oct. 31, 2014 USD ($)	Oct. 31, 2014 EUR (€)	Jul. 31, 2005 USD ($)	Dec. 31, 2015 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Sanofi Upfront Payment	$ 300,000,000
Sanofi Development and Regulatory Milestone Payments	430,000,000
Sanofi Sales Milestone Payments	990,000,000
Sanofi Development Costs Funded by Lexicon Maximum Amount	100,000,000
Sanofi Revenue Allocated to License Deliverable	126,800,000
Sanofi Revenue Allocated to Development Deliverable	113,800,000
Sanofi Revenue Allocated to Funding Deliverable	$ 59,400,000
Sanofi Revenue Recognized					$ 126,800,000
Ipsen Total Upfront Payments		$ 24,500,000
Ipsen Revenue Allocated to License Deliverable		21,200,000
Ipsen Maximum Regulatory And Commercial Milestones		34,000,000
Ipsen Revenue Allocated to Development Deliverable		1,700,000
Ipsen Revenue Allocated to Committee Deliverable		$ 100,000
Ipsen Revenue Recognized					21,400,000
Ipsen Maximum Sales Milestones | €			€ 72
TX Enterprise Fund Award				$ 35,000,000
TX Enterprise Fund Award to Texas AM University System				$ 15,000,000
TIGM Per Job Payment Amount					2,415
TIGM Maximum Exposure					14,200,000
TIGM Maximum Exposure Through Reporting Date					$ 6,400,000