Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Preferred stock and convertible preferred stock

Preferred stock and convertible preferred stock consist of the following: 

	6/30/2019		12/31/2018
Preferred stock, $0.001 par value; 5,000,000 shares authorized at June 30, 2019 and December 31, 2018; no shares issued and outstanding at June 30, 2019 and December 31, 2018	$	—	$	—
Series B convertible preferred stock, $0.001 par value; 147,000 shares designated at June 30, 2019 and December 31, 2018; 200 shares issued and outstanding at June 30, 2019 and December 31, 2018	$	1	$	1
Series D convertible preferred stock, $0.001 par value; 21,300 shares designated at June 30, 2019 and December 31, 2018; 11,054.73 and 14,052.93 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	$	10	$	14
Series E convertible preferred stock, $0.001 par value; 7,000 shares designated at June 30, 2019 and December 31, 2018; zero and 3,260.70 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	$	—	$	3