Debt Obligations	9 Months Ended
Sep. 30, 2017
Debt Obligations [Abstract]
Debt Disclosure	Debt Obligations Convertible Debt. In November 2014, Lexicon completed an offering of $87.5 million in aggregate principal amount of its 5.25% Convertible Senior Notes due 2021 (the “Notes”). The conversion feature did not meet the criteria for bifurcation as required by generally accepted accounting principles and the entire principal amount was recorded as long-term debt on the Company’s consolidated balance sheets. The Notes are governed by an indenture (the “Indenture”), dated as of November 26, 2014, between the Company and Wells Fargo Bank, N.A., as trustee. The Notes bear interest at a rate of 5.25% per year, payable semiannually in arrears on June 1 and December 1 of each year, beginning on June 1, 2015. The Notes mature on December 1, 2021. The Company may not redeem the Notes prior to the maturity date, and no sinking fund is provided for the Notes. Holders of the Notes may convert their Notes at their option at any time prior to the close of business on the business day immediately preceding the maturity date. Upon conversion, the Company will deliver for each $1,000 principal amount of converted Notes a number of shares of its common stock equal to the conversion rate, as described in the Indenture. The conversion rate is initially 118.4553 shares of common stock per $1,000 principal amount of Notes (equivalent to an initial conversion price of $8.442 per share of common stock). The conversion rate is subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, the Company will increase the conversion rate for a holder who elects to convert its Notes in connection with such a corporate event in certain circumstances. If the Company undergoes a fundamental change, holders may require the Company to repurchase for cash all or any portion of their Notes at a fundamental change repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In connection with the issuance of the Notes, the Company incurred $3.4 million of debt issuance costs, which offsets long-term debt on the consolidated balance sheets. The debt issuance costs are amortized as interest expense over the expected life of the Notes using the effective interest method. The Company determined the expected life of the debt was equal to the seven-year term of the Notes. As of September 30, 2017, the balance of unamortized debt issuance costs was $2.0 million. The fair value of the Notes was $141.6 million as of September 30, 2017 and was determined using Level 2 inputs based on the indicative pricing published by certain investment banks or trading levels of the Notes, which are not listed on any securities exchange or quoted on an inter-dealer automated quotation system. Mortgage Loan. In April 2004, Lexicon obtained a $34.0 million mortgage on its facilities in The Woodlands, Texas. The mortgage loan originally had a ten-year term with a 20-year amortization and a fixed interest rate of 8.23%. The mortgage was amended in September 2013 to extend the maturity date from April 2014 to April 2017, with the mortgage loan’s monthly payment amount and fixed interest rate each remaining unchanged. In April 2017, the mortgage was amended to extend the maturity date to April 2018, with the mortgage loan’s monthly payment amount and fixed interest rate each remaining unchanged. The mortgage had a principal balance outstanding of $14.7 million as of September 30, 2017. This entire balance is recorded as current portion of long-term debt in the accompanying consolidated balance sheet as of September 30, 2017 as there is a balloon payment due in April 2018. The buildings and land that serve as collateral for the mortgage loan are included in property and equipment at $59.2 million and $2.7 million, respectively, before accumulated depreciation, as of September 30, 2017. The fair value of Lexicon’s mortgage loan approximates its carrying value. The fair value of Lexicon’s mortgage loan was determined using Level 2 inputs using discounted cash flow analysis, based on the Company’s estimated current incremental borrowing rate.

Debt Obligations

Convertible Debt. In November 2014, Lexicon completed an offering of $87.5 million in aggregate principal amount of its 5.25% Convertible Senior Notes due 2021 (the “Notes”). The conversion feature did not meet the criteria for bifurcation as required by generally accepted accounting principles and the entire principal amount was recorded as long-term debt on the Company’s consolidated balance sheets.

The Notes are governed by an indenture (the “Indenture”), dated as of November 26, 2014, between the Company and Wells Fargo Bank, N.A., as trustee. The Notes bear interest at a rate of 5.25% per year, payable semiannually in arrears on June 1 and December 1 of each year, beginning on June 1, 2015. The Notes mature on December 1, 2021. The Company may not redeem the Notes prior to the maturity date, and no sinking fund is provided for the Notes.

Holders of the Notes may convert their Notes at their option at any time prior to the close of business on the business day immediately preceding the maturity date. Upon conversion, the Company will deliver for each $1,000 principal amount of converted Notes a number of shares of its common stock equal to the conversion rate, as described in the Indenture. The conversion rate is initially 118.4553 shares of common stock per $1,000 principal amount of Notes (equivalent to an initial conversion price of $8.442 per share of common stock). The conversion rate is subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, the Company will increase the conversion rate for a holder who elects to convert its Notes in connection with such a corporate event in certain circumstances.

If the Company undergoes a fundamental change, holders may require the Company to repurchase for cash all or any portion of their Notes at a fundamental change repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

In connection with the issuance of the Notes, the Company incurred $3.4 million of debt issuance costs, which offsets long-term debt on the consolidated balance sheets. The debt issuance costs are amortized as interest expense over the expected life of the Notes using the effective interest method. The Company determined the expected life of the debt was equal to the seven-year term of the Notes. As of September 30, 2017, the balance of unamortized debt issuance costs was $2.0 million.

The fair value of the Notes was $141.6 million as of September 30, 2017 and was determined using Level 2 inputs based on the indicative pricing published by certain investment banks or trading levels of the Notes, which are not listed on any securities exchange or quoted on an inter-dealer automated quotation system.

Mortgage Loan. In April 2004, Lexicon obtained a $34.0 million mortgage on its facilities in The Woodlands, Texas. The mortgage loan originally had a ten-year term with a 20-year amortization and a fixed interest rate of 8.23%. The mortgage was amended in September 2013 to extend the maturity date from April 2014 to April 2017, with the mortgage loan’s monthly payment amount and fixed interest rate each remaining unchanged. In April 2017, the mortgage was amended to extend the maturity date to April 2018, with the mortgage loan’s monthly payment amount and fixed interest rate each remaining unchanged. The mortgage had a principal balance outstanding of $14.7 million as of September 30, 2017. This entire balance is recorded as current portion of long-term debt in the accompanying consolidated balance sheet as of September 30, 2017 as there is a balloon payment due in April 2018. The buildings and land that serve as collateral for the mortgage loan are included in property and equipment at $59.2 million and $2.7 million, respectively, before accumulated depreciation, as of September 30, 2017. The fair value of Lexicon’s mortgage loan approximates its carrying value. The fair value of Lexicon’s mortgage loan was determined using Level 2 inputs using discounted cash flow analysis, based on the Company’s estimated current incremental borrowing rate.