Subsequent Events	6 Months Ended
Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Authorized Shares and Reverse Stock Split - The Company’s board of directors and stockholders approved an amended and restated certificate of incorporation to effect a 2-for-3 reverse stock split of the Company’s Class B common stock on July 5, 2018 and July 18, 2018, respectively. The Company filed the amended and restated certificate of incorporation on July 19, 2018 which effected the 2-for-3 reverse stock split and reduced the authorized number of shares for both Class A common stock and Class B common stock from 600,000,000 shares to 400,000,000 shares for each class. The financial statements have been retroactively adjusted for all periods presented to give effect to the reverse stock split, including reclassifying an amount equal to the reduction in par value of Class B common stock to accumulated deficit. Initial Public Offering - In July 2018, the Company successfully completed an initial public stock offering (IPO) with the sale of 20,700,000 shares of Class A common stock, at a price of $15.00 per share, resulting in net cash proceeds of $284.3 million, net of underwriting discounts and commissions. 8% Convertible Promissory Notes Converted (8% Notes) - In July 2018, the $221.6 million, including principal and accrued interest, of outstanding 8% Notes automatically converted into shares of Class B common stock upon which which were convertible. See Note 6 - Outstanding Loans and Security Agreements for details. Upon the Company's IPO, the original notes converted to shares of Series G convertible preferred stock at a conversion price of $38.64 per share and, concurrently, each such share of Series G convertible preferred stock converted automatically into one share of Class B common stock. 5,734,440 shares of Class B common stock were issued from conversions and the debt was retired. Convertible Preferred Stock - Shares of the Company's convertible preferred stock were convertible into an equal number of shares of Class B common stock upon the completion of the IPO in July 2018. 71,740,162 shares of Class B common stock were issued from the conversion of convertible preferred stock. Warrants - On August 31, 2017 and in connection with the issuance of the 6% Convertible Promissory Notes, the Company issued common stock warrants to CPPIB to purchase up to 312,888 shares of the Company’s common stock. All the warrants were exercised for Class B Common stock upon the completion of the IPO in July 2018. Litigation - In July 2018, the Company received a Statement of Claim from two former executives of Advanced Equities, Inc. seeking to compel arbitration and alleging a breach of a confidential agreement from June 2014. This Statement of Claim sought, among other things, to void the indemnification and confidentiality provisions under the confidential agreement and to recover attorneys’ fees and costs. The Statement of Claim was dismissed without prejudice on July 22, 2018.

Subsequent Events

Authorized Shares and Reverse Stock Split - The Company’s board of directors and stockholders approved an amended and restated certificate of incorporation to effect a 2-for-3 reverse stock split of the Company’s Class B common stock on July 5, 2018 and July 18, 2018, respectively. The Company filed the amended and restated certificate of incorporation on July 19, 2018 which effected the 2-for-3 reverse stock split and reduced the authorized number of shares for both Class A common stock and Class B common stock from 600,000,000 shares to 400,000,000 shares for each class. The financial statements have been retroactively adjusted for all periods presented to give effect to the reverse stock split, including reclassifying an amount equal to the reduction in par value of Class B common stock to accumulated deficit.

Initial Public Offering - In July 2018, the Company successfully completed an initial public stock offering (IPO) with the sale of 20,700,000 shares of Class A common stock, at a price of $15.00 per share, resulting in net cash proceeds of $284.3 million, net of underwriting discounts and commissions.

8% Convertible Promissory Notes Converted (8% Notes) - In July 2018, the $221.6 million, including principal and accrued interest, of outstanding 8% Notes automatically converted into shares of Class B common stock upon which which were convertible. See Note 6 - Outstanding Loans and Security Agreements for details. Upon the Company's IPO, the original notes converted to shares of Series G convertible preferred stock at a conversion price of $38.64 per share and, concurrently, each such share of Series G convertible preferred stock converted automatically into one share of Class B common stock. 5,734,440 shares of Class B common stock were issued from conversions and the debt was retired.

Convertible Preferred Stock - Shares of the Company's convertible preferred stock were convertible into an equal number of shares of Class B common stock upon the completion of the IPO in July 2018. 71,740,162 shares of Class B common stock were issued from the conversion of convertible preferred stock.

Warrants - On August 31, 2017 and in connection with the issuance of the 6% Convertible Promissory Notes, the Company issued common stock warrants to CPPIB to purchase up to 312,888 shares of the Company’s common stock. All the warrants were exercised for Class B Common stock upon the completion of the IPO in July 2018.

Litigation - In July 2018, the Company received a Statement of Claim from two former executives of Advanced Equities, Inc. seeking to compel arbitration and alleging a breach of a confidential agreement from June 2014. This Statement of Claim sought, among other things, to void the indemnification and confidentiality provisions under the confidential agreement and to recover attorneys’ fees and costs. The Statement of Claim was dismissed without prejudice on July 22, 2018.