Stockholders' Equity - June 2017 Private Placement (Details) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 30, 2017 USD ($) Vote $ / shares shares	Jun. 30, 2018 USD ($) $ / shares	Jun. 30, 2017 USD ($) Vote $ / shares	Dec. 31, 2017 $ / shares
Stockholders' Equity
Net proceeds after deducting commissions and other transactions costs | $		$ 311,825	$ 38,278
Preferred Stock, Par or Stated Value Per Share		$ 0.0001		$ 0.0001
Series A Convertible Preferred Stock
Stockholders' Equity
Preferred Stock, Par or Stated Value Per Share	$ 0.0001		$ 0.0001
Preferred stock conversion ratio | shares	1
Preferred shares number voting rights | Vote	0		0
Private Placement Offering | Purchase Agreement
Stockholders' Equity
Value of shares sold by the entity | $	$ 35,000
Net proceeds after deducting commissions and other transactions costs | $	$ 34,900
Private Placement Offering | Common stock | Purchase Agreement
Stockholders' Equity
Number of shares sold by the entity | shares	328,300
Issue price of stock	$ 15.23		$ 15.23
Private Placement Offering | Series A Convertible Preferred Stock | Purchase Agreement
Stockholders' Equity
Number of shares sold by the entity | shares	1,969,797
Issue price of stock	$ 15.23		$ 15.23