Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended				12 Months Ended
	Oct. 17, 2019	Apr. 26, 2019	Jun. 26, 2018	Oct. 31, 2019	Apr. 30, 2019	Jul. 31, 2018	Aug. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Apr. 23, 2019	Aug. 08, 2017	Dec. 31, 2016
Preferred stock, shares authorized								50,000,000		50,000,000
Preferred stock, shares issued								0		0
Preferred stock, shares outstanding								0		0
Common stock, shares authorized								750,000,000		750,000,000
Common stock, par value (in dollars per share)								$ 0.0001		$ 0.0001
Common stock, shares issued	5,714,286	789,473		5,714,286	5,263,158	4,500,000		62,083,000		78,004,669	5,263,158
Common stock, shares outstanding								62,083,000		78,004,669
Issuance of common stock in exchange for commitment to provide debt financing									$ 2,448
Stock price (in dollars per share)												$ 8.16
Issuance of common stock upon exercise of warrants (in shares)			332,896			332,896
Issuance of common stock upon exercise of warrants						$ 6,800		$ 6,762
Stock issued (in dollars per share)	$ 35			$ 35	$ 19	$ 20					$ 19
Payment of offering expenses	$ 400	$ 600		$ 400	$ 600	$ 500
Proceeds from issuance of common stock	$ 216,200	$ 108,100		$ 216,200	$ 108,100	$ 97,300
Option for additional shares
Common stock, shares issued	857,142	789,473		857,142		675,000
Common stock
Common stock, shares issued								62,083,000	54,040,000	78,005,000			52,665,000
Issuance of common stock in exchange for commitment to provide debt financing (in shares)							300,000,000		300,000
Issuance of common stock in exchange for commitment to provide debt financing							$ 2,400
Issuance of common stock upon exercise of warrants (in shares)								333,000