Collaboration and License Agreements (Details) € in Millions	1 Months Ended					12 Months Ended
	Aug. 31, 2016 USD ($)	Nov. 30, 2015 USD ($)	Oct. 31, 2014 USD ($)	Oct. 31, 2014 EUR (€)	Jul. 31, 2005 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Sanofi Upfront Payment		$ 300,000,000
Sanofi Development Milestones		110,000,000
Sanofi Regulatory Milestones		220,000,000
Sanofi Outcomes Study Milestone		100,000,000
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						$ 75,400,000	$ 126,800,000
Sanofi Sales of Clinical Trial Materials						6,300,000
Sanofi Accounts Receivable						4,500,000
Ipsen Total Payments To Date						30,900,000
Ipsen Total Upfront Payments			$ 24,500,000
Ipsen Milestone Payment Received	$ 6,400,000
Ipsen Revenue Allocated to License Deliverable			21,200,000				1,400,000
Ipsen Maximum Regulatory And Commercial Milestones			27,000,000
Ipsen Revenue Allocated to Development Deliverable			1,700,000
Ipsen Revenue Allocated to Committee Deliverable			$ 100,000
Ipsen Revenue Recognized						7,200,000	$ 2,300,000	$ 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						$ 10,300,000