Stockholders' Equity (Deficit) - Registered Offering (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2017
Stockholders' Equity (Deficit)
Value of shares sold by the entity			$ 173,805
Registered Offering | Common stock | Goldman Sachs & Co. LLC | Underwriting Agreement
Stockholders' Equity (Deficit)
Number of shares sold by the entity	1,079,580	1,731,929
Number of days granted to purchase additional shares	30 days	30 days
Issue price of stock	$ 305.00	$ 83.00	$ 83.00
Value of shares sold by the entity	$ 329,300	$ 143,800
Net proceeds after deducting commissions and other transactions costs	$ 311,800	$ 135,700
Additional Shares | Common stock | Goldman Sachs & Co. LLC | Underwriting Agreement
Stockholders' Equity (Deficit)
Number of shares sold by the entity	95,973	225,904