Convertible Preferred Stock	12 Months Ended
Convertible Preferred Stock	Dec. 31, 2019
Equity [Abstract]
Convertible Preferred Stock	Convertible Preferred Stock The Company previously issued convertible preferred stock in one or more series, each with such designations, rights, qualifications, limitations, and restrictions as set forth in the Company’s certificate of incorporation, as in effect prior to the IPO. Immediately prior to the completion of the IPO, as described in Note 1, Description of Business, all shares of convertible preferred stock then outstanding were automatically converted to 58,264,577 shares of common stock at the respective conversion ratios in October 2018. In May 2017, the Company entered into the Series E convertible preferred stock purchase agreement with SoftBank and certain of the Company’s existing stockholders. Pursuant to the purchase agreement, the Company issued and sold an aggregate of 38,174,246 shares of Series E convertible preferred stock at a purchase price of $8.3936 per share, for an aggregate purchase price of $320.4 million. The purchase agreement also provided that the Company would issue additional shares of Series E convertible preferred stock to the Series E investors in such an amount as to cause SoftBank’s equity ownership in the Company to equal 35% of the Company’s outstanding fully-diluted capital stock measured 70 days after the initial closing. This gross-up was intended to enable the Company to engage in various repurchases of its equity from existing stockholders and still maintain SoftBank’s equity ownership at 35%. As a result, in July 2017, the Company repurchased an aggregate of 1,588,065 shares of common stock from certain of its directors and executive officers for a purchase price of $10.23887 per share, which represented a price equal to 90% of the original price per shares for the Series E convertible preferred stock, as adjusted to reflect the 0.7378-for-one reverse stock split of the Company’s common stock effected on September 19, 2018. The Company also engaged in a tender offer pursuant to which it repurchased 131,243 shares of common stock from certain employees at the same per share price paid for the Series E convertible preferred stock as adjusted to reflect the 0.7378-for-one reverse stock split of the Company’s common stock effected on September 19, 2018, and 666,920 shares of Series A convertible preferred stock from existing stockholders at a purchase price of $8.00 per share of Series A convertible preferred stock. Following these repurchases, in October 2017, the Company issued an additional 796,346 shares of Series E convertible preferred stock to the Series E investors for a purchase price of $0.00001 per share pursuant to the terms of the gross up provision. The conversion price of Series E convertible preferred stock was adjusted as a result of the dilutive issuance of Series E convertible preferred stock under the gross up provision. In May 2017, in accordance with its certificate of incorporation then in effect, the Company adjusted the conversion price of Series D convertible preferred stock from $10.1338 per share to $9.8329 per share. The Company accounted for the transaction as a modification. A deemed dividend of $1.1 million, calculated as the additional 253,361 shares of common stock to be received upon the conversion of the Series D convertible preferred stock after the conversion ratio adjustment, multiplied by the then current fair value of the Company’s common stock, was reported as an increase to net loss attributable to common stockholders for the year ended December 31, 2018. Repurchase of Series A Convertible Preferred Stock During the year ended December 31, 2017, the Company repurchased 666,920 shares of outstanding Series A convertible preferred stock at a price of $8.00 per share for a total consideration of $5.3 million. The difference between the repurchase amount and the carrying value of these shares of $4.7 million was recorded as a deemed dividend in accumulated deficit on the accompanying consolidated statements of stockholders’ equity.