Stockholders' Equity (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended						9 Months Ended
	Oct. 31, 2019	Nov. 30, 2017	May 31, 2016	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Common Stock
Aggregate offering price stock sale			$ 60,000
Additional offering price stock sale authorized		$ 75,000
Net proceeds from sale of common stock										$ 13,826	$ 25,453
Common Stock
Common Stock
Shares Issued in Connection with Cantor Agreement (in shares)				1,087,603	1,972,428	883,569	787,163	884,068	312,802	3,900,000
Aggregate gross offering price available				$ 23,200						$ 23,200
Net proceeds from sale of common stock										$ 13,800
Common Stock | Subsequent Event
Common Stock
Common stock issued (in shares)	200,000
Net proceeds from sale of common stock	$ 500