Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information [Table Text Block]

	Year Ended December 31, 2018
	First		Second		Third		Fourth
Revenue	$	1,503	$	608	$	281	$	1,767
Operating expenses	$	5,418	$	8,383	$	6,161	$	5,953
Net income (loss)	$	2,314	$	(8,871)	$	(6,548)	$	(4,902)
Net income (loss) attributable to common stockholders	$	1,975	$	(8,871)	$	(6,548)	$	(4,902)
Net income (loss) per share – basic	$	0.54	$	(1.24)	$	(0.92)	$	(0.69)
Net income (loss) per share – diluted	$	0.49	$	(1.24)	$	(0.92)	$	(0.69)

	Year Ended December 31, 2017
	First		Second		Third		Fourth
Revenue	$	2,310	$	1,854	$	915	$	760
Operating expenses	$	4,557	$	4,977	$	2,871	$	3,449
Net loss	$	(2,796)	$	(3,538)	$	(2,173)	$	(1,075)
Net loss attributable to common stockholders	$	(3,506)	$	(4,256)	$	(2,898)	$	(1,800)
Net loss per share – basic and diluted	$	(25.84)	$	(31.37)	$	(21.36)	$	(13.16)