Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Preferred stock and convertible preferred stock

Preferred stock and convertible preferred stock consist of the following: 

	March 31, 2018		December 31, 2017
Preferred stock, $0.001 par value; 5,000,000 shares authorized at March 31, 2018 and December 31, 2017; no shares issued and outstanding at March 31, 2018 and December 31, 2017	$	—	$	—
Series B convertible preferred stock, $0.001 par value, 147,000 shares designated at March 31, 2018 and December 31, 2017, and 500 shares issued and outstanding at March 31, 2018 and December 31, 2017	$	1	$	1
Series D convertible preferred stock, $0.001 par value, 21,300 shares designated at March 31, 2018 and December 31, 2017, 14,052.93 shares issued and outstanding at March 31, 2018 and December 31, 2017	$	14	$	14
Series E convertible preferred stock, $0.001 par value, 7,000 shares designated at March 31, 2018 and December 31, 2017, respectively, and 3,260.70 and 7,000 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	$	3	$	7
Series F convertible preferred stock, $0.001 par value, 10,621 shares designated at March 31, 2018 and December 31, 2017, zero and 7,927.05 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	$	—	$	8