Recent Accounting Pronouncements	12 Months Ended
Dec. 31, 2017
Recent Accounting Pronouncements [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, “Revenue from Contracts with Customers”, which amends FASB ASC Topic 606. ASU 2014-09 provides a single, comprehensive revenue recognition model for all contracts with customers. This standard contains principles for the determination of the measurement of revenue and the timing of when such revenue is recognized. Revenue recognition will reflect the transfer of goods or services to customers at an amount that is expected to be earned in exchange for those goods or services. In August 2015, the FASB issued ASU No. 2015-14, “Revenue from Contracts with Customers: Deferral of Effective Date”, which defers the effective date of ASU 2014-09 by one year. ASU 2014-09 is now effective for annual periods after December 15, 2017 including interim periods within that reporting period. Early application is permitted only for annual periods beginning after December 15, 2016, including interim periods within that reporting period. In 2016, the FASB issued four additional ASUs related to Topic 606: ASU Nos. 2016-08, 2016-10, 2016-12 and 2016-20. These ASUs clarify various aspects of the new revenue guidance, including principal versus agent considerations, identifying performance obligations and licensing, and they include other improvements and practical expedients. Two adoption methods are permitted; retrospectively to all prior reporting periods presented, with certain practical expedients; or the modified retrospective method with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company has elected to adopt this new standard effective January 1, 2018, using the modified retrospective transition method. To date, the Company has assessed that ASU 2014-09 will not have a material impact on revenue recognition from product revenue. The Company’s only source of product revenue has been sales of XERMELO, which the Company received FDA approval for in February 2017, and subsequently, entered into a limited number of arrangements with specialty pharmacies (“SPs”) in the U.S. (collectively, the “customers”), under which the Company began shipping to its customers in March 2017. Under current GAAP, the Company recognizes revenue on its product sales when the customer obtains control of the product, which occurs upon delivery. Product revenue is recorded net of applicable reserves for variable consideration, including discounts and allowances. These estimates are based on the most likely amount method for relevant factors such as current contractual and statutory requirements, industry data and forecasted customer buying and payment patterns. The Company’s net product revenues reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the respective underlying contracts. Under ASU 2014-09, the Company expects to be able to utilize a process and controls approach consistent with its historical process and based on the nature of its current contracts with customers, does not anticipate a significant amount of variable consideration subject to constraint. As a result, the Company does not believe that the adoption of this ASU will have a material impact on the timing or amount of revenues recognized related to its contracts with customers for the sale of product. The Company expects the accounting for contingent milestone payments to be the most significant change in the accounting for its license and collaboration agreements. Topic 605 provides guidance specific to the accounting for milestone payments, including the ability to defer the recognition of any milestones until received and, if certain criteria are met, the ability to recognize milestone payments as revenue when received. Under the Company’s current accounting policy, Lexicon recognizes contingent or milestone payments as revenue in the period that the payment-triggering event occurs or is achieved. However, under the new revenue standard, it is possible to recognize contingent or milestone payments before the payment-triggering event is completely achieved, subject to management’s assessment of the probability of achievement of the milestone and the likelihood of a significant reversal of such milestone revenue at each reporting date. This assessment may result in recognizing milestone revenue before the milestone event has been achieved. The Company expects to evaluate estimates and timing of milestone achievement and related variable consideration based on the most likely amount method in its application of this ASU to collaborative agreements. Estimating variable consideration and the related constraint will require the use of significant management judgment. To date, the Company’s primary sources of collaboration revenue have been license and collaboration agreements with three separate third-party licensees: Texas Institute for Genomic Medicine (“TIGM”), Sanofi and Ipsen. The Company has performed an evaluation of the expected effect of adoption in its accounting for license and collaboration agreements as discussed further below. With respect to its contract with TIGM, the Company evaluated the variable consideration related to the remaining milestone in the adoption of this ASU and determined based on the most likely amount method that it was not probable that a significant reversal would occur and therefore, no constraint was required. As a result, under the modified retrospective method, the Company will record a $14.2 million cumulative-effect adjustment to its accumulated deficit on the date of adoption. With respect to its collaboration agreements with Sanofi and Ipsen, the Company evaluated the variable consideration relating to future milestone payments and determined, based on the most likely amount method, that the estimated amounts could be considered as part of the transaction price. The Company then evaluated the variable constraint and determined that the variable consideration amounts are constrained, primarily by future events that are not within the control of the Company. The future events primarily related to receipt of positive results from studies, approval from regulatory agencies, and upon achieving sales in certain locations. As a result, the Company has determined that there is no cumulative adjustment necessary for these agreements on the date of adoption. The adoption of the ASU will have no significant impact to the provision for income taxes and will have no impact to the net cash provided by or used in operating, investing or financing activities on the Company’s consolidated statements of cash flows. Estimated impacts from adoption of this ASU may differ upon the final adoption and implementation in the first quarter of 2018. As the Company completes its analysis of the accounting for the collaboration agreements under the new revenue standard, management is assessing the required changes to its accounting policies, systems and internal control over financial reporting. In January 2016, the FASB issued ASU No. 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 requires that most equity investments be measured at fair value, with subsequent changes in fair value recognized in net income. The pronouncement also impacts financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is not permitted. The adoption of this ASU on January 1, 2018 is not expected to have a material impact on Lexicon’s consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, “Leases.” ASU 2016-02 requires companies that lease assets to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments, in its balance sheet. The pronouncement will also require additional disclosures about the amount, timing and uncertainty of cash flows arising from leases. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. This ASU is required to be adopted using a modified retrospective approach. Management plans to adopt ASU 2016-02 on January 1, 2019, and anticipates that most of its operating leases will result in the recognition of additional assets and corresponding liabilities on the consolidated balance sheet. The Company does not expect that the implementation of the ASU will have a material impact on its financial position. The actual impact will depend on the Company’s lease portfolio at the time of adoption. The Company continues to assess all implications of the standard and related financial disclosures. In March 2016, the FASB issued ASU No. 2016-09, “Stock Compensation,” which is intended to simplify several aspects of the accounting for share-based payment award transactions. The Company adopted this pronouncement effective January 1, 2017. Upon adoption, the Company recognized approximately $6.1 million of accumulated excess tax benefits as deferred tax assets that under the previous guidance could not be recognized until the benefits were realized through a reduction in cash taxes paid. This part of the guidance is applied using a modified retrospective method with a cumulative-effect adjustment to the accumulated deficit for the excess tax benefits not previously recognized. However, given the full valuation allowance placed on the additional $6.1 million of deferred tax assets, the recognition of this provision of ASU 2016-09 had no impact to the Company’s accumulated deficit as of January 1, 2017. Additionally, the Company recorded an adjustment to accumulated deficit of $2.0 million as a result of making an entity-wide accounting policy election to account for forfeitures of share-based payment awards as they occur instead of estimating the number of awards that are expected to vest.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, “Revenue from Contracts with Customers”, which amends FASB ASC Topic 606. ASU 2014-09 provides a single, comprehensive revenue recognition model for all contracts with customers. This standard contains principles for the determination of the measurement of revenue and the timing of when such revenue is recognized. Revenue recognition will reflect the transfer of goods or services to customers at an amount that is expected to be earned in exchange for those goods or services. In August 2015, the FASB issued ASU No. 2015-14, “Revenue from Contracts with Customers: Deferral of Effective Date”, which defers the effective date of ASU 2014-09 by one year. ASU 2014-09 is now effective for annual periods after December 15, 2017 including interim periods within that reporting period. Early application is permitted only for annual periods beginning after December 15, 2016, including interim periods within that reporting period. In 2016, the FASB issued four additional ASUs related to Topic 606: ASU Nos. 2016-08, 2016-10, 2016-12 and 2016-20. These ASUs clarify various aspects of the new revenue guidance, including principal versus agent considerations, identifying performance obligations and licensing, and they include other improvements and practical expedients. Two adoption methods are permitted; retrospectively to all prior reporting periods presented, with certain practical expedients; or the modified retrospective method with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company has elected to adopt this new standard effective January 1, 2018, using the modified retrospective transition method.

To date, the Company has assessed that ASU 2014-09 will not have a material impact on revenue recognition from product revenue. The Company’s only source of product revenue has been sales of XERMELO, which the Company received FDA approval for in February 2017, and subsequently, entered into a limited number of arrangements with specialty pharmacies (“SPs”) in the U.S. (collectively, the “customers”), under which the Company began shipping to its customers in March 2017. Under current GAAP, the Company recognizes revenue on its product sales when the customer obtains control of the product, which occurs upon delivery. Product revenue is recorded net of applicable reserves for variable consideration, including discounts and allowances. These estimates are based on the most likely amount method for relevant factors such as current contractual and statutory requirements, industry data and forecasted customer buying and payment patterns. The Company’s net product revenues reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the respective underlying contracts. Under ASU 2014-09, the Company expects to be able to utilize a process and controls approach consistent with its historical process and based on the nature of its current contracts with customers, does not anticipate a significant amount of variable consideration subject to constraint. As a result, the Company does not believe that the adoption of this ASU will have a material impact on the timing or amount of revenues recognized related to its contracts with customers for the sale of product.

The Company expects the accounting for contingent milestone payments to be the most significant change in the accounting for its license and collaboration agreements. Topic 605 provides guidance specific to the accounting for milestone payments, including the ability to defer the recognition of any milestones until received and, if certain criteria are met, the ability to recognize milestone payments as revenue when received. Under the Company’s current accounting policy, Lexicon recognizes contingent or milestone payments as revenue in the period that the payment-triggering event occurs or is achieved. However, under the new revenue standard, it is possible to recognize contingent or milestone payments before the payment-triggering event is completely achieved, subject to management’s assessment of the probability of achievement of the milestone and the likelihood of a significant reversal of such milestone revenue at each reporting date. This assessment may result in recognizing milestone revenue before the milestone event has been achieved. The Company expects to evaluate estimates and timing of milestone achievement and related variable consideration based on the most likely amount method in its application of this ASU to collaborative agreements. Estimating variable consideration and the related constraint will require the use of significant management judgment.

To date, the Company’s primary sources of collaboration revenue have been license and collaboration agreements with three separate third-party licensees: Texas Institute for Genomic Medicine (“TIGM”), Sanofi and Ipsen. The Company has performed an evaluation of the expected effect of adoption in its accounting for license and collaboration agreements as discussed further below.

With respect to its contract with TIGM, the Company evaluated the variable consideration related to the remaining milestone in the adoption of this ASU and determined based on the most likely amount method that it was not probable that a significant reversal would occur and therefore, no constraint was required. As a result, under the modified retrospective method, the Company will record a $14.2 million cumulative-effect adjustment to its accumulated deficit on the date of adoption.

With respect to its collaboration agreements with Sanofi and Ipsen, the Company evaluated the variable consideration relating to future milestone payments and determined, based on the most likely amount method, that the estimated amounts could be considered as part of the transaction price. The Company then evaluated the variable constraint and determined that the variable consideration amounts are constrained, primarily by future events that are not within the control of the Company. The future events primarily related to receipt of positive results from studies, approval from regulatory agencies, and upon achieving sales in certain locations. As a result, the Company has determined that there is no cumulative adjustment necessary for these agreements on the date of adoption.

The adoption of the ASU will have no significant impact to the provision for income taxes and will have no impact to the net cash provided by or used in operating, investing or financing activities on the Company’s consolidated statements of cash flows. Estimated impacts from adoption of this ASU may differ upon the final adoption and implementation in the first quarter of 2018. As the Company completes its analysis of the accounting for the collaboration agreements under the new revenue standard, management is assessing the required changes to its accounting policies, systems and internal control over financial reporting.

In January 2016, the FASB issued ASU No. 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 requires that most equity investments be measured at fair value, with subsequent changes in fair value recognized in net income. The pronouncement also impacts financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is not permitted. The adoption of this ASU on January 1, 2018 is not expected to have a material impact on Lexicon’s consolidated financial statements.

In February 2016, the FASB issued ASU No. 2016-02, “Leases.” ASU 2016-02 requires companies that lease assets to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments, in its balance sheet. The pronouncement will also require additional disclosures about the amount, timing and uncertainty of cash flows arising from leases. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. This ASU is required to be adopted using a modified retrospective approach. Management plans to adopt ASU 2016-02 on January 1, 2019, and anticipates that most of its operating leases will result in the recognition of additional assets and corresponding liabilities on the consolidated balance sheet. The Company does not expect that the implementation of the ASU will have a material impact on its financial position. The actual impact will depend on the Company’s lease portfolio at the time of adoption. The Company continues to assess all implications of the standard and related financial disclosures.

In March 2016, the FASB issued ASU No. 2016-09, “Stock Compensation,” which is intended to simplify several aspects of the accounting for share-based payment award transactions. The Company adopted this pronouncement effective January 1, 2017. Upon adoption, the Company recognized approximately $6.1 million of accumulated excess tax benefits as deferred tax assets that under the previous guidance could not be recognized until the benefits were realized through a reduction in cash taxes paid. This part of the guidance is applied using a modified retrospective method with a cumulative-effect adjustment to the accumulated deficit for the excess tax benefits not previously recognized. However, given the full valuation allowance placed on the additional $6.1 million of deferred tax assets, the recognition of this provision of ASU 2016-09 had no impact to the Company’s accumulated deficit as of January 1, 2017. Additionally, the Company recorded an adjustment to accumulated deficit of $2.0 million as a result of making an entity-wide accounting policy election to account for forfeitures of share-based payment awards as they occur instead of estimating the number of awards that are expected to vest.