Organization and Description of Business (Details Narrative) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended	12 Months Ended
	Aug. 31, 2018	Aug. 13, 2018	Mar. 31, 2019	Dec. 31, 2017	Dec. 31, 2018	Jun. 01, 2018	Nov. 30, 2017	Nov. 21, 2017	Dec. 08, 2016
exercise price (in dollars per share)			$ 1.15
Proceeds from issuance and sale of common stock, preferred stock, warrants exercise, convertible and other promissory notes			$ 61,800
Proceeds from licensing fees			1,700
Proceeds from product sales			400
Accumulated deficit			(88,202)		$ (85,838)
Cash, cash equivalents and short-term investments			$ 2,900
Common Stock Offering Warrants Issued
Initial Public Offering [Member]
Number of shares issued									1,875,000
Initial Public Offering [Member] | Common Stock Purchase Warrants [Member]
Number of shares issued									187,500
exercise price (in dollars per share)									$ 9.60
Public Offering [Member]
Number of shares issued								5,860,000
exercise price (in dollars per share)								$ 1.00
Shares issued per share (in dollars per share)								$ 1.00
Public Offering [Member] | Common Stock Purchase Warrants [Member] | Investor [Member]
Number of shares issued								4,657,500
exercise price (in dollars per share)								$ 1.50
Public Offering [Member] | Common Stock Purchase Warrants [Member] | Roth Capital Partners, LLC [Member]
Number of shares issued								945,000
exercise price (in dollars per share)								$ 1.50
Private placement [Member] | Common Stock Purchase Warrants [Member]
Number of shares issued						1,133,909	1,133,909
exercise price (in dollars per share)						$ 1.82	$ 1.50
Right Offering [Member]
exercise price (in dollars per share)	$ 1.15
Unit price (in dollars per unit)	1.15
Common Stock Offering Warrants Issued		5,357,052
Right Offering [Member] | Common Stock Purchase Warrants [Member] | Maxim Partners LLC [Member]
exercise price (in dollars per share)	$ 1.725
Number of subscriptions shares accept	5,357,052
Common Stock Offering Warrants Issued	267,853