Collaboration and License Agreements (Details) $ in Thousands, € in Millions	1 Months Ended					6 Months Ended		12 Months Ended
	Aug. 31, 2016 USD ($)	Nov. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Oct. 31, 2014 EUR (€)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Collaboration and License Agreements [Abstract]
Sanofi Upfront Payment		$ 300,000
Sanofi Development Milestones		110,000
Sanofi Regulatory Milestones		220,000
Sanofi Outcomes Study Milestone		100,000
Sanofi Sales Milestone Payments		990,000
Sanofi Commercialization Costs Funded by Lexicon Maximum Amount		100,000
Sanofi Revenue Allocated to License Deliverable		126,800
Sanofi Revenue Allocated to Development Deliverable		113,800
Sanofi Revenue Allocated to Funding Deliverable		$ 59,400
Sanofi Revenue Recognized						$ 24,100	$ 31,700
Ipsen Total Payments						30,900
Ipsen Maximum Regulatory And Commercial Milestones				$ 27,000
Ipsen Maximum Sales Milestones | €					€ 72
Ipsen Total Upfront Payments			$ 24,500
Ipsen Milestone Payment	$ 6,400
Ipsen Revenue Allocated to License Deliverable								$ 1,400	$ 21,200
Ipsen Revenue Allocated to Development Deliverable				1,700
Ipsen Revenue Allocated to Committee Deliverable				$ 100
Ipsen Revenue Recognized						1,400	$ 200
Ipsen Product Sales						$ 300