Revenue Recognition	9 Months Ended
Revenue Recognition	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition Pursuant to Topic 606, we recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, Topic 606 includes provisions within a five step model that includes i) identifying the contract with a customer, ii) identifying the performance obligations in the contract, iii) determining the transaction price, iv) allocating the transaction price to the performance obligations, and v) recognizing revenue when, or as, an entity satisfies a performance obligation. At contract inception, we assess the goods or services promised within each contract and assess whether each promised good or service is distinct and determine those that are performance obligations. We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when the performance obligation is satisfied. Everest Medicines II Limited: On April 29, 2019, the Company entered into a license agreement (the “License Agreement”) with Everest Medicines II Limited, a China limited company (“Everest”). Pursuant to the License Agreement, the Company granted Everest an exclusive license to develop and commercialize sacituzumab govitecan in the People’s Republic of China, Taiwan, Hong Kong, Macao, Indonesia, Philippines, Vietnam, Thailand, South Korea, Malaysia, Singapore and Mongolia (the "Territory"). In consideration for entering into the License Agreement, Everest made a one-time, non-refundable upfront payment to the Company in the aggregate amount of $65.0 million which is recorded as deferred revenue. The License Agreement contains a development milestone payment of $60.0 million based upon the Company’s achievement of FDA approval for sacituzumab govitecan in mTNBC. The License Agreement also contains additional development milestone payments in a total amount of up to $180.0 million based upon the achievement of certain other development milestones. In addition, the License Agreement contains sales milestone payments in a total amount of up to $530.0 million based upon the achievement of certain sales milestones. Everest will make royalty payments to the Company based upon percentages of net sales of sacituzumab govitecan, ranging from 14% to 20%. The Company assessed the arrangement in accordance with ASC 606 and concluded that the contract counterparty, Everest, is a customer based on the arrangement structure. The Company identified two material promises to deliver under the contract: (1) grant of license and the (2) clinical and commercial supply of the product. However, given the nature of the manufacturing of the product the license is not considered to be distinct from the clinical and commercial supply promise. The Company therefore concluded that there is one combined performance obligation. The Company initially deferred and will recognize the $65.0 million over the performance obligation period of the combined performance obligation. As it relates to the upfront consideration, the $65.0 million is recorded as deferred revenue and will be recognized over the term of the of the contract performance obligation period, which the Company has concluded to be 15 years after initial sale of the product in the territory. As concluded above, the Company has a combined performance obligation, which includes delivering the license and clinical and commercial supply to Everest. As such, because the clinical and commercial supply obligation occur throughout the period of the License Agreement, the $65.0 million fixed consideration is recognized over the period in which commercial and clinical supply of product is delivered (over-time). The future potential milestone payments are excluded from the transaction price, as the achievement of the milestone events require considerable judgment in determining whether it is probable of being achieved, and that a significant revenue reversal would not occur. As such, all milestone payments are fully constrained. The Company will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjust its estimate of the transaction price. Janssen Biotech Inc.: On April 5, 2019, the Company entered into a promotion agreement (the “Promotion Agreement”) with Janssen Biotech Inc., ("Janssen") pursuant to which the Company will provide non-exclusive product detailing services to Janssen for erdafitinib (the “Product”). Pursuant to the Promotion Agreement, the Company will provide a dedicated sales team to market the Product, upon approval by the FDA, to oncologists and other targeted health care providers in the United States. Under the terms of the Promotion Agreement, Janssen maintains ownership of the New Drug Application for the Product as well as legal, regulatory, distribution, commercialization and manufacturing responsibilities for the Product, while the Company will provide product detailing services to Janssen. Following the achievement of certain sales targets in 2019 and 2020, Janssen will pay the Company (a) a service fee equal to a percentage in the low double digits of the portion of Cumulative Net Sales (as defined in the Promotion Agreement) in excess of a baseline amount during each of 2019 and 2020, and (b) potential milestone payments of up to $15.0 million when Cumulative Net Sales exceed certain thresholds during each of 2019 and 2020. On April 12, 2019, the Company was informed that the FDA granted accelerated approval to Janssen's Balversa (erdafitinib) for the treatment of adult patients with locally advanced or metastatic urothelial carcinoma that has a type of susceptible genetic alteration known as FGFR3 or FGFR2, and that has progressed during or following prior platinum-containing chemotherapy. During the three and nine months ended September 30, 2019, no revenues were recorded relating to the Promotion Agreement.