Statements of Redeemable Convertible Preferred Stock and Stockholders Equity (Deficit) - USD ($)	Total	Common Stock	Additional Paid-In-Capital (Distributions in Excess of Capital)	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit	Series D Warrants	Series E Warrants	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Series C-1 Redeemable Convertible Preferred Stock	Series C-2 Redeemable Convertible Preferred Stock	Series D Redeemable Convertible Preferred Stock	Series D Redeemable Convertible Preferred Stock Series D Warrants	Series E Redeemable Convertible Preferred Stock	Series E Redeemable Convertible Preferred Stock Series E Warrants
Balance at Dec. 31, 2013	$ (58,251,910)	$ 97	$ (3,966,712)	$ (75,000)		$ (54,210,295)			$ 1,401,677	$ 3,795,690	$ 5,596,660	$ 4,270,835	$ 35,803,437
Balance, shares at Dec. 31, 2013		96,349							1,292,084	11,919,624	16,240,450	19,104,610	143,737,467
Issuance of preferred stock Series E	0														$ 5,494,766
Issuance of preferred stock Series E, Shares															34,453,538
Exercise of Series D and Series E warrants							$ 0	$ 0						$ 4,271		$ 1,889,201
Exercise of Series D and Series E warrants, shares														25,125		11,484,503
Exercise of stock options	21,482	$ 10	21,472
Exercise of stock options, shares		9,909
Share-based compensation expense	184,966		184,966
Accretion of redeemable convertible preferred stock issuance costs	(102,677)		(102,677)						$ 1,010	$ 2,647	$ 4,853	$ 6,665	$ 57,049		$ 30,453
Accretion of Series E warrant discount	(313,152)		(313,152)					313,152							313,152
Adjustment to Series B book value	112,903		112,903							(112,903)
Accretion of Series D and E redeemable convertible preferred stock dividend	(3,244,572)		(3,244,572)										2,517,245		727,327
Optional conversion of preferred stock to common										$ (1,586,124)	$ (1,033,988)	$ (2,053,994)	$ (1,207,336)
Optional conversion of preferred stock to common, shares										(5,129,912)	(2,997,838)	(9,156,279)	(4,233,419)
Net loss	(13,958,408)					(13,958,408)
Balance at Dec. 31, 2014	(69,669,926)	$ 333	(1,426,556)	(75,000)		(68,168,703)			$ 1,402,687	$ 2,099,310	$ 4,567,525	$ 2,223,506	$ 37,174,666		$ 8,454,899
Balance, shares at Dec. 31, 2014		332,607							1,292,084	6,789,712	13,242,612	9,948,331	139,529,173		45,938,041
Optional conversion of preferred stock to common	5,881,442	$ 226	5,881,216
Optional conversion of preferred stock to common, shares		226,349
Exercise of Series D and Series E warrants								0					$ 93,550		$ 11,312
Exercise of Series D and Series E warrants, shares													723,505		51,681
Exercise of stock options	34,881	$ 14	34,867
Exercise of stock options, shares		13,960
Share-based compensation expense	405,426		405,426
Accretion of redeemable convertible preferred stock issuance costs	(35,046)		(35,046)						$ 320	$ 839	$ 1,538	$ 2,113	$ 18,109		$ 12,127
Accretion of Series E warrant discount	(127,616)		(127,616)					$ 127,616							127,616
Accretion of Series D and E redeemable convertible preferred stock dividend	(1,165,932)		(1,165,932)										876,955		288,977
Optional conversion of preferred stock to common	57,356,049	$ 2,509	57,353,540						$ (1,403,007)	$ (2,100,149)	$ (4,569,063)	$ (2,225,619)	$ (38,163,280)		$ (8,894,931)
Optional conversion of preferred stock to common, shares		2,508,824							(1,292,084)	(6,789,712)	(13,242,612)	(9,948,331)	(140,252,678)		(45,989,722)
Net loss	(21,397,791)					(21,397,791)
Balance at Dec. 31, 2015	16,893,398	$ 6,844	106,569,405	$ (75,000)	$ (41,357)	$ (89,566,494)
Balance, shares at Dec. 31, 2015		6,844,242
Conversion of outstanding principal and accrued interest on convertible notes to common stock	4,544,384	$ 324	4,544,060
Conversion of warrants from warrants for preferred stock to warrants for common stock	1,616,140		1,616,140
Issuance of common stock from initial public offering	45,354,186	$ 3,660	45,350,526
Issuance of common stock from initial public offering, shares		3,660,076
Other comprehensive income	(41,357)				$ (41,357)
Stock issued under stock purchase plan	$ 20,000	$ 4	$ 19,996
Stock issued under stock purchase plan, shares	4,184	4,184
Settlement of outstanding principal and accrued interest on convertible notes by issuance of common stock, shares		324,591