Stockholders' Equity (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	May 31, 2016
Stockholders' Equity
Net proceeds from sale of common stock		$ 32,642	$ 10,666
Controlled Equity Offering Sales Agreement | Common Stock
Stockholders' Equity
Aggregate offering price of common stock				$ 60,000
Common stock issued (in shares)		11,326,363
Net proceeds from sale of common stock		$ 32,600
Aggregate gross offering price available		$ 11,700
Controlled Equity Offering Sales Agreement | Common Stock | Subsequent Event
Stockholders' Equity
Common stock issued (in shares)	3,871,709
Net proceeds from sale of common stock	$ 11,300