Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended
	Jul. 16, 2018	Jul. 31, 2018	Apr. 30, 2016	Jul. 12, 2018	Jun. 30, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Common stock, shares issued					55,454,000	54,040,000
Agreement extension term			4 years
Subsequent Event
Subsequent Event [Line Items]
Agreement extension term		3 years
Minimum committed fees		$ 3.0
Subsequent Event | July 2018 Offering
Subsequent Event [Line Items]
Common stock, shares issued				4,500,000
Stock price				$ 20
Subsequent Event | Option for additional shares
Subsequent Event [Line Items]
Common stock, shares issued				675,000
Subsequent Event | July 2018 Offering inclusive of option for additional shares
Subsequent Event [Line Items]
Proceeds from issuance of common stock	$ 96.6
Payment of offering costs	$ 0.7