Stockholders' Equity - Shelf Registration Statement, Private Placement, and ATM Sales Agreement (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2019	Jan. 31, 2019	Nov. 02, 2018
Sale of stock
Proceeds from issuance of common stock in private placement, net of offering costs				$ 7,810
Proceeds from At-the-Market sales of common stock, net of offering costs				2,249
Common Stock
Sale of stock
Issuance of common stock (in shares)		992,072
Private Placement | Common Stock
Sale of stock
Issuance of common stock (in shares)	8,426,750		8,426,750
Share price (in dollars per share)	$ 0.93		$ 0.93
Proceeds from issuance of common stock in private placement, net of offering costs	$ 7,800
At-the-market sales
Sale of stock
Commission payable on sale of stock (as a percent)					3.00%
Proceeds from At-the-Market sales of common stock, net of offering costs		$ 1,400		$ 2,200
At-the-market sales | Maximum
Sale of stock
Authorized value for shares issuance					$ 10,000
At-the-market sales | Common Stock
Sale of stock
Issuance of common stock (in shares)		992,072	665,974	1,658,046
2018 Shelf Offering
Sale of stock
Aggregate amount of securities issuable						$ 100,000