Statement of Changes in Convertible Preferred Stock and Stockholders' Deficit - 6 months ended Jun. 30, 2018 - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ (192,652)		$ 2	$ 4,292	$ (196,946)
Beginning balance, shares at Dec. 31, 2017			231,000
Beginning balance, shares at Dec. 31, 2017	304,958,000	304,958,000
Beginning balance at Dec. 31, 2017	$ 187,136	$ 187,136
Exercises of stock options	38		$ 1	37
Exercises of stock options, shares			26,000
Share-based compensation expense	336			336
Net loss	(12,993)				(12,993)
Ending balance at Jun. 30, 2018	$ (205,271)		$ 3	$ 4,665	$ (209,939)
Ending balance, shares at Jun. 30, 2018			257,000
Ending balance, shares at Jun. 30, 2018	304,958,000	304,958,000
Ending balance at Jun. 30, 2018	$ 187,136	$ 187,136