License Revenue and Reimbursable Expenses	9 Months Ended
License Revenue and Reimbursable Expenses	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License Revenue and Reimbursable Expenses	License Revenue and Reimbursable Expenses General The Company has generated revenue from contracts with customers, which include upfront payments for licenses. Berlin-Chemie On July 23, 2020, the Company entered into a license agreement (“License Agreement”) with Berlin-Chemie under which the Company granted Berlin-Chemie an exclusive license to develop and commercialize products containing elacestrant (RAD1901) worldwide. The Company and Berlin-Chemie simultaneously entered into a Transition Services Agreement (the “TSA”), pursuant to which the Company agreed to perform certain services for Berlin-Chemie related to the EMERALD Phase 3 monotherapy study until the earlier of the completion of the contemplated services or the filing with the FDA of a New Drug Application for elacestrant. Pursuant to the TSA, Berlin-Chemie agreed to reimburse the Company for all out-of-pocket and full-time employee costs in performing the services, for total estimated reimbursements of $111.5 million. The Company will continue to incur research and development expenses in support of scale up costs under the TSA. Pursuant to the terms of the License Agreement, Berlin-Chemie made a nonrefundable initial license fee payment to the Company of $30.0 million in July 2020. The Company is also eligible to receive up to $20.0 million in development and regulatory milestone payments and up to $300.0 million in sales milestone payments, with such payments contingent on the achievement of specified milestones with respect to the licensed products. The Company is also eligible to receive tiered royalties on sales of licensed products at percentages ranging from low to mid-teens, subject to certain reductions. Royalties on net sales will be payable on a product-by-product and country-by-country basis until the latest of the expiration date of the last to expire of the relevant patent rights, the expiration of regulatory exclusivity, or ten years from such first commercial sale. The License Agreement will continue on a licensed product-by-licensed product and country-by-country basis until the last to expire royalty term. Either party may terminate the License Agreement for an uncured material breach by the other party or upon the bankruptcy or insolvency of the other party. The Company may terminate the License Agreement for certain patent challenges or if no development, manufacture or commercialization activity occurs in any given 24-month period. Berlin-Chemie may terminate the License Agreement at its discretion for any reason by delivering 180 days’ prior written notice to the Company; provided that such termination will not be effective prior to the third anniversary of the effective date. The Company determined that the License Agreement and TSA should be combined and evaluated as a single arrangement as they were executed on the same date and negotiated as a package. The arrangement with Berlin-Chemie provides for the transfer of the following goods or services: (i) license, (ii) know-how, (iii) regulatory filings, (iv) inventory, (v) transition services, including certain clinical, manufacturing, regulatory and other services associated with the Phase 3 EMERALD monotherapy study, and (vi) participation in various joint committees. Management applied the guidance in ASC 606 to identify all distinct goods and services within the arrangement to assess whether there is a unit of account that should be accounted for under ASC 606. Management evaluated all of the promised goods or services within the contract and determined which of those were separate performance obligations. The Company determined that the license granted, at arrangement inception, should be combined with the know-how and regulatory filings as they are not capable of being distinct (the “License”). The Company also concluded that the license rights, know-how, and regulatory filings are capable of being distinct from the supply of inventory, as Berlin-Chemie would be able to benefit from the inventory on its own or with other resources that are readily available, and capable of being distinct from the transition services and participation in joint committees as these are research and development services that can typically be performed by other third parties. The License is an element of the arrangement that is subject to the revenue recognition accounting guidance, as the performance obligation is an output of the Company’s ordinary activities in exchange for consideration. Conversely, the transition services, the participation on joint committees, and transfer of inventory are elements of the arrangements that are outside the scope of the revenue recognition guidance, as the Company is providing goods and services that are not an output of the Company’s ordinary activities. The transaction price at inception is comprised of fixed consideration of $30.0 million. The $30.0 million upfront fee, which represents the fixed consideration in the transaction price, was allocated to the License and the supply of inventory, on a relative standalone selling price basis. The Company estimated the standalone selling price for the license by applying a risk adjusted, net present value, estimate of future potential cash flows approach and determined the standalone selling price for the inventory using a cost approach. Accordingly, the Company has allocated $27.4 million to the license and $2.6 million to the inventory. The Company concluded that the reimbursements for the research and development transition services and participation in the joint steering committees was commensurate with the standalone selling prices of the services, and as such, will be attributed to those services. The reimbursements for these services will be recorded as a reduction of the related research and development expenses as the expenses are incurred. Under the Berlin-Chemie agreements, the Company is eligible to receive various development and regulatory, and sales milestones. There is uncertainty that the events to obtain the development and regulatory milestones will be achieved. The Company has thus determined that all such milestones will be constrained until it is deemed probable that a significant revenue reversal will not occur. Additional transaction price recognized in future periods related to milestone payments and royalties will be allocated solely to the License. Sales milestones and sales-based royalties were also excluded from the transaction price as the license is deemed to be the predominant item to which the sales milestones and sales-based royalties relate. The Company will recognize such revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). During the three and nine months ended September 30, 2020, the Company recognized $27.4 million of license revenue, as it had satisfied its promises under the performance obligation for the license, including the transfer of know-how and regulatory filings, by transferring them at a point in time during the quarter. During the three and nine months ended September 30, 2020, the Company recorded $15.4 million as a reduction of research and development expenses for reimbursement of transition services performed under the TSA.