Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Follow On Public Offering [Member]	Common Stock [Member]	Common Stock [Member] Follow On Public Offering [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Follow On Public Offering [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, Value at Dec. 31, 2014	$ 51,662		$ 23		$ 131,840		$ (80,201)
Balance, Shares at Dec. 31, 2014			22,802,039
Sale of common stock net of underwriting discounts and commissions and offering expenses, Value		$ 75,231		$ 4		$ 75,227
Sale of common stock, net of underwriting discounts and commissions and offering expenses, Shares				4,327,956
Stock-based compensation expense	1,807				1,807
Shares issued upon exercise of stock options, Value	323				323
Shares issued upon exercise of stock options, Shares			101,588
Net loss	(15,160)						(15,160)
Balance, Value at Sep. 30, 2015	113,863		$ 27		209,197		(95,361)
Balance, Shares at Sep. 30, 2015			27,231,583
Balance, Value at Dec. 31, 2015	105,044		$ 27		209,943		(104,891)	$ (35)
Balance, Shares at Dec. 31, 2015			27,254,863
Stock-based compensation expense	1,971				1,971
Shares issued upon exercise of stock options, Value	40				40
Shares issued upon exercise of stock options, Shares			28,000
Net loss	(35,308)						(35,308)
Other comprehensive income	55							55
Balance, Value at Sep. 30, 2016	$ 71,802		$ 27		$ 211,954		$ (140,199)	$ 20
Balance, Shares at Sep. 30, 2016			27,282,863