STOCKHOLDERS' EQUITY (Details Narrative) - USD ($)									12 Months Ended
	Sep. 28, 2017	Sep. 25, 2017	Jan. 12, 2016	Jan. 06, 2016	Jul. 15, 2015	Jul. 09, 2015	Feb. 17, 2015	Feb. 10, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Preferred stock, par value (in dollars per share)									$ 0.001	$ 0.001
Preferred stock, shares authorized									10,000,000	10,000,000
Preferred stock, shares issued									0	0
Preferred stock, shares outstanding									0	0
Common stock, shares authorized									350,000,000	350,000,000
Common stock, shares issued									216,429,642	196,688,222
Common stock, shares outstanding									216,429,642	196,688,222
Value of common stock issued during period for stock options exercised									$ 212,615	$ 989,060	$ 1,232,579
Number of stock options exercised (in shares)									102,546	523,362
Proceeds from sale of common stock, net of costs									$ 68,572,635	$ 134,863,475	91,374,649
Number of stock options exercised in cashless exercise (in shares)										127,109
Number of common stock issued during period for stock options exercised in cashless exercise (in shares)										87,833
Stock Options [Member]
Value of common stock issued during period for stock options exercised											$ 1,232,579
Number of stock options exercised (in shares)											612,867
Number of stock options exercised in cashless exercise (in shares)											417
Number of common stock issued during period for stock options exercised in cashless exercise (in shares)											114
Underwriting Agreement - J.P. Morgan Securities LLC [Member]
Number of shares offered in underwriting agreement		12,400,000
Number of shares issued during the period	12,400,000
Share price (in dollars per share)		$ 5.55
Proceeds from sale of common stock, net of costs		$ 68,573,000
Underwriting Agreement - Goldman and Cowen [Member]
Number of shares offered in underwriting agreement				15,151,515
Number of shares issued during the period			17,424,242
Share price (in dollars per share)				$ 8.25
Proceeds from sale of common stock, net of costs				$ 134,864,000
Additional common stock issued under offering				2,272,727
Number of days of the option to purchase shares				30 days
Stifel Underwriters [Member]
Number of shares offered in underwriting agreement						3,846,154
Number of shares issued during the period					4,423,077
Share price (in dollars per share)						$ 7.80
Proceeds from sale of common stock, net of costs						$ 32,257,000
Additional common stock issued under offering						576,923
Number of days of the option to purchase shares						30 days
Cowen and Company, LLC (Underwriters) [Member]
Number of shares offered in underwriting agreement								13,580,246
Number of shares issued during the period							15,617,282
Share price (in dollars per share)								$ 4.05
Proceeds from sale of common stock, net of costs								$ 59,118,000
Additional common stock issued under offering								2,037,036
Number of days of the option to purchase shares								30 days