BASIS OF PRESENTATION (Policies)	9 Months Ended
BASIS OF PRESENTATION (Policies)	Sep. 30, 2017
BASIS OF PRESENTATION
Use of Estimates	Use of Estimates The preparation of these unaudited condensed consolidated financial statements requires management to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures. On an ongoing basis, the Company evaluates its estimates, including critical accounting policies or estimates related to available-for-sale securities, debt instruments, research and development expenses, income taxes, inventories, revenues, contingencies and litigation and share-based compensation. The Company bases its estimates on historical experience, information received from third parties and on various market specific and other relevant assumptions that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ significantly from those estimates under different assumptions or conditions.
Available-for-Sale Securities	As of September 30, 2017, the Company’s available-for-sale securities had original contractual maturities up to 67 months. However, the Company may sell these securities prior to their stated maturities in response to changes in the availability of and the yield on alternative investments as well as liquidity requirements. As these securities are readily marketable and are viewed by the Company as available to support current operations, securities with maturities beyond 12 months are classified as current assets. Due to their short-term maturities, the Company believes that the fair value of its bank deposits, accounts payable and accrued expenses approximate their carrying value.
Inventories	In July 2015, the FASB issued Accounting Standards Update 2015-11, Simplifying the Measurement of Inventory - Inventory (Topic 330), which changes the measurement principle for inventory from the lower of cost or market to the lower of cost or net realizable value. Net realizable value is defined as the “estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation.” This standard eliminates the guidance that entities consider replacement cost or net realizable value less an approximately normal profit margin in the subsequent measurement of inventory when cost is determined on a first-in, first-out or average cost basis. The Company adopted this standard in the first quarter of 2017 and it did not have a material impact on the Company’s condensed consolidated financial statements.
Revenue Recognition	Revenue Recognition Product Revenue: The Company recognizes product revenue when: (i)persuasive evidence that an arrangement exists, (ii)delivery has occurred and title has passed, (iii)the price is fixed or determinable, and (iv)collectability is reasonably assured. Revenue from sales transactions where the customer has the right to return the product is recognized at the time of sale only if: (i) the Company’s price to the customer is substantially fixed or determinable at the date of sale, (ii) the customer has paid the Company, or the customer is obligated to pay the Company and the obligation is not contingent on resale of the product, (iii) the customer’s obligation to the Company would not be changed in the event of theft or physical destruction or damage of the product, (iv) the customer acquiring the product for resale has economic substance apart from that provided by the Company, (v) the Company does not have significant obligations for future performance to directly bring about resale of the product by the customer, and (vi) the amount of future returns can be reasonably estimated. Product revenue is recognized net of consideration paid to the Company’s customers, wholesalers and certified pharmacies. Such consideration is for services rendered by the wholesalers and pharmacies in accordance with the wholesalers and certified pharmacy services network agreements, and includes a fixed rate per prescription shipped and monthly program management and data fees. These services are not deemed sufficiently separable from the customers’ purchase of the product; therefore, they are recorded as a reduction of revenue at the time of revenue recognition.
Product Revenue Allowance	Other product revenue allowances include certain prompt pay discounts and allowances offered to the Company’s customers, program rebates and chargebacks. These product revenue allowances are recognized as a reduction of revenue at the later of the date at which the related revenue is recognized or the date at which the allowance is offered. The Company also offers discount programs to patients. Calculating certain of these items involves estimates and judgments based on sales or invoice data, contractual terms, utilization rates, new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates or chargebacks. The Company reviews the adequacy of product revenue allowances on a quarterly basis. Amounts accrued for product revenue allowances are adjusted when trends or significant events indicate that adjustment is appropriate and to reflect actual experience.
Revenue Recognition, Sales Returns	The Company ships units of Qsymia through a distribution network that includes certified retail pharmacies. The Company began shipping Qsymia in September 2012 and grants rights to its customers to return unsold product from six months prior to and up to 12 months subsequent to product expiration. This has resulted in a potential return period of from 24 to 36 months depending on the ship date of the product. As the Company had no previous experience in selling Qsymia and given its lengthy return period, the Company was not initially able to reliably estimate expected returns of Qsymia at the time of shipment, and therefore recognized revenue when units were dispensed to patients through prescriptions, at which point, the product is not subject to return, or when the expiration period had ended. Beginning in the first quarter of 2017, with 48 months of returns experience, the Company now believes that it has sufficient data and experience from selling Qsymia to reliably estimate expected returns. Therefore, beginning in the first quarter of 2017, the Company began recognizing revenue from the sales of Qsymia upon shipment and recording a reserve for expected returns at the time of shipment. In accordance with this change in accounting estimate, the Company recognized a one-time adjustment of $7.3 million of revenues, net of expected returns reserve and gross-to-net charges, in the first quarter of 2017 relating to products that had been previously shipped. This increase in net product revenue resulted in a decrease in net loss of $6.0 million or $0.06 per share for the nine months ended September 30, 2017.
Share-based compensation	In March 2016, the FASB issued Accounting Standards Update 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. This standard is intended to simplify several areas of accounting for share-based compensation arrangements, including the income tax impact, classification on the statement of cash flows and forfeitures. The Company adopted this standard in the first quarter of 2017, and it did not have a material impact on the Company’s condensed consolidated financial statements.
Income Taxes	The Company’s policy is to recognize interest and penalties related to uncertain tax positions (if any) as a component of the income tax provision.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers. This standard is a comprehensive new revenue recognition model that requires revenue to be recognized in a manner to depict the transfer of goods or services to a customer at an amount that reflects the consideration expected to be received in exchange for those goods or services. This new standard will supersede most current revenue recognition guidance. In July 2015, the FASB voted to delay the effective date of this standard by one year to the first quarter of 2018. Early adoption is permitted, but not before the first quarter of 2017. This new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized in retained earnings as of the date of adoption, or the “modified retrospective basis.” The Company plans to adopt this standard in the first quarter of 2018 using the modified retrospective basis. The Company has analyzed the effect of this standard on its consolidated financial statements and currently does not expect the adoption of this standard to have a material impact on the Company’s net product revenues and supply revenues in the first quarter of adoption or on the timing of future recognition of net product revenues and supply revenues, as the Company expects that revenues generated will continue to be recognized upon the shipment of products to customers. Similarly, the Company does not expect a material impact on the recognition of royalty revenue. The Company does not expect the adoption of this standard to have a material impact on the Company’s license and milestone revenue in the first quarter of adoption; however, the Company does expect that the timing of recognition of future milestone revenue related to current license and supply agreements as well as the timing and allocation of revenue related to any future license and supply agreements entered into by the Company may be impacted. In February 2016, the FASB issued Accounting Standards Update 2016-02, Leases (Topic 842), which modifies the accounting by lessees for all leases with a term greater than 12 months. This standard will require lessees to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. For public companies, this standard is effective for annual and interim periods beginning on or after December 15, 2018. Early adoption is permitted. The Company’s only significant lease is its operating lease for its corporate headquarters, and, while the Company cannot yet estimate the amounts by which its financial statements will be affected by the adoption of this guidance, it expects that the overall recognition of expense will be similar to current guidance, though possibly in different classifications, but that there will be a significant change in the balance sheet due to the recognition of right of use assets and the corresponding lease liabilities. The Company plans to adopt the new leases guidance effective January 1, 2019 using a modified retrospective transition method. In August 2016, the FASB issued Accounting Standards Update 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments. The standard clarifies how certain cash receipts and cash payments will be presented and classified in the statement of cash flows. The new standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is permitted. The Company is currently evaluating the impact that the standard will have on its consolidated financial statements.