Stockholders' Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended			6 Months Ended
	Mar. 31, 2020	Feb. 29, 2020	Aug. 31, 2019	Jan. 31, 2019	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Nov. 02, 2018
Sale of stock
Proceeds from issuance of common stock in private placement, net of offering costs									$ 7,810
Commission percentage				3.00%
2018 Shelf Registration Statement
Sale of stock
Aggregate amount of securities issuable										$ 100,000
Private Placement | Common Stock
Sale of stock
Issuance of common stock (in shares)	8,426,750				17,250,000		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
Issuance of common stock (in shares)									1,658,046
Gross Proceeds									$ 2,200
Proceeds from issuance of common stock in public offering, net of offering costs									(2,249)
At-the-market sales | Common Stock
Sale of stock
Issuance of common stock (in shares)						992,072	665,974
Public offering
Sale of stock
Proceeds from issuance of common stock in public offering, net of offering costs								$ 48,434
Public offering | Common Stock
Sale of stock
Issuance of common stock (in shares)		17,250,000	14,526,315
Share price (in dollars per share)		$ 3.00	$ 0.95
Proceeds from issuance of common stock in public offering, net of offering costs		$ 48,400	$ 12,700
At The Market Offering
Sale of stock
Issuance of common stock (in shares)						992,072
Gross Proceeds				$ 10,000
Proceeds from issuance of common stock in public offering, net of offering costs									$ 1,400