CONDENSED STATEMENT OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($)	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Deficit	Total
Balance at beginning of period at Dec. 31, 2016			$ (41,196)
Net loss					$ (46,500,131)
Unrealized gain on securities					36,636
Balance at end of period at Sep. 30, 2017			(4,560)
Balance at beginning of period at Jun. 30, 2017			(34,863)
Net loss					(23,266,818)
Unrealized gain on securities					30,303
Balance at end of period at Sep. 30, 2017			(4,560)
Cumulative effect of adoption of ASC 606 | ASU 2014-09				$ 339,406	339,406
Balance after adjustment	$ 48,204	$ 404,454,909	(64,433)	(308,615,129)	95,823,551
Balance at beginning of period at Dec. 31, 2017	$ 48,204	404,454,909	(64,433)	(308,954,535)	95,484,145
Balances (in shares) at Dec. 31, 2017	48,203,529
Exercise of stock options	$ 1,517	9,837,268			9,838,785
Exercise of stock options (in shares)	1,516,796
Issuance of common stock in connection with equity offering	$ 31,414	269,794,204			269,825,618
Issuance of common stock in connection with equity offering (in shares)	31,414,093
Stock-based compensation	$ 163	4,346,471			4,346,634
Stock-based compensation (in shares)	163,530
Employee stock purchase plan	$ 25	95,045			95,070
Employee stock purchase plan (in shares)	25,352
Net loss				(32,774,814)	(32,774,814)
Unrealized gain on securities			41,749		41,749
Balance at end of period at Sep. 30, 2018	$ 81,323	688,527,897	(22,684)	(341,389,943)	$ 347,196,593
Balances (in shares) at Sep. 30, 2018	81,323,300
Balance at beginning of period at Jun. 30, 2018			(34,324)
Exercise of stock options (in shares)					442,913
Net loss					$ (12,607,525)
Unrealized gain on securities					11,640
Balance at end of period at Sep. 30, 2018	$ 81,323	$ 688,527,897	$ (22,684)	$ (341,389,943)	$ 347,196,593
Balances (in shares) at Sep. 30, 2018	81,323,300