Cover Page - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Mar. 06, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	000-30111
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	76-0474169
Entity Address, Address Line One	8800 Technology Forest Place
City Area Code	(281)
Local Phone Number	863-3000
Entity Address, City or Town	The Woodlands
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77381
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 259,500
Documents Incorporated by Reference	Certain sections of the registrant’s definitive proxy statement relating to the registrant’s 2020 annual meeting of stockholders, which proxy statement will be filed under the Securities Exchange Act of 1934 within 120 days of the end of the registrant’s fiscal year ended December 31, 2019, are incorporated by reference into Part III of this annual report on Form 10-K.
Entity Registrant Name	Lexicon Pharmaceuticals, Inc.
Entity Central Index Key	0001062822
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Trading Symbol	LXRX
Entity Common Stock, Shares Outstanding		106,969,973