Quarterly Financial Information (unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information [Table Text Block]

	March 31,		June 30,		September 30,		December 31,
2016 Quarter Ended
Revenue	$	—	$	—	$	—	$	—
Operating expenses		13,139		12,989		10,812		11,627
Other income, net		100		118		118		152
Net loss		(13,039)		(12,871)		(10,694)		(11,475)
Net loss attributable to common stockholders	$	(13,039)	$	(12,871)	$	(10,694)	$	(11,475)
Net loss per share attributable to common stockholders, basic and diluted	$	(0.65)	$	(0.62)	$	(0.50)	$	(0.49)
2015 Quarter Ended
Revenue	$	—	$	—	$	—	$	—
Operating expenses		2,629		2,596		10,640		4,802
Other income, net		6		2		7		89
Net loss		(2,623)		(2,594)		(10,632)		(4,714)
Net loss attributable to common stockholders	$	(3,280)	$	(3,270)	$	(11,652)	$	(4,927)
Net loss per share attributable to common stockholders, basic and diluted	$	(1.61)	$	(1.52)	$	(5.12)	$	(0.28)