Capital Structure - Common Stock (Details)						3 Months Ended	12 Months Ended
	Nov. 17, 2017 USD ($) shares	Apr. 27, 2017 USD ($) $ / shares shares	Sep. 08, 2016 USD ($) $ / shares shares	Nov. 23, 2015 USD ($) shares	Oct. 20, 2015 USD ($) class_of_stock $ / shares shares	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) class_of_stock Vote $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Jan. 27, 2017 USD ($)	Aug. 31, 2014 $ / shares shares
Common Stock
Number of classes of stock authorized to issue | class_of_stock					2
Number of shares of capital stock authorized to issue (in shares)							205,000,000
Common stock, shares authorized (in shares)							200,000,000	200,000,000
Preferred stock, shares authorized (in shares)							5,000,000	0
Common stock, par value (in dollars per share) | $ / shares							$ 0.001	$ 0.001
Preferred stock, par value per share (in dollars per share) | $ / shares							$ 0.001	$ 0.001
Initial Public Offering [Abstract]
Gross proceeds | $				$ 135,319			$ 1,502,593	$ 1,899,987	$ 21,165,589
Underwriter's Unit Purchase Option [Abstract]
Threshold price per common stock on any trading day to present notice for purchase of common stock | $ / shares			$ 0.50
Number of shares sold under purchase agreement (in shares)							31,266,989	9,434,141
Proceeds from issuance of common stock | $							$ 1,693,498	$ 2,003,182
Common stock
Common Stock
Number of shares available under warrant (in shares)											22,328
Initial Public Offering [Abstract]
Exercise price per share (in dollars per share) | $ / shares											$ 8.40
Issuance of stock (in shares)							2,301,598	763,998	4,020,000
Gross proceeds | $							$ 2,302	$ 764	$ 4,020
Aspire Capital Fund LLC (Aspire Capital)
Underwriter's Unit Purchase Option [Abstract]
Term of common stock purchase agreement			30 months
Common stock issued as commitment fee			175,000
Capital Unit
Initial Public Offering [Abstract]
Exercise price per share (in dollars per share) | $ / shares					$ 5.23
Issuance of stock (in shares)					4,000,000
Share price (in dollars per share) | $ / shares					$ 6.50
Gross proceeds | $					$ 26,000,000
Net proceeds from IPO | $					23,600,000
Underwriter's Unit Purchase Option [Abstract]
Proceeds from unit purchase option | $					$ 100
Units available, as a percentage of units sold					1.00%
Equity purchase option unit, exercise price per unit | $ / shares					$ 7.48
Equity purchase option unit, exercise price as percent of IPO price					115.00%
Capital Unit, Class B
Initial Public Offering [Abstract]
Exercise price per share (in dollars per share) | $ / shares					$ 4.49
Class A Warrant
Initial Public Offering [Abstract]
Number of equity instruments included in a unit					1
Exercise price per share (in dollars per share) | $ / shares					$ 4.55
Issuance of stock (in shares)				551,900
Underwriter's Unit Purchase Option [Abstract]
Equity purchase option, unit exercise price after first warrant expiration | $ / shares					7.475
Equity purchase option, unit exercise price after second warrant expiration | $ / shares					$ 7.47
Class B Warrant
Initial Public Offering [Abstract]
Number of equity instruments included in a unit					1
Exercise price per share (in dollars per share) | $ / shares					$ 3.90
Issuance of stock (in shares)				551,900
Common Stock
Common Stock
Number of shares available under warrant (in shares)							18,986,859
Initial Public Offering [Abstract]
Number of equity instruments included in a unit					1
Issuance of stock (in shares)				20,000
Underwriter's Unit Purchase Option [Abstract]
Number of votes per share | Vote							1
Number of preemptive, conversion or subscription rights | class_of_stock							0
Number of redemption or sinking fund provisions | class_of_stock							0
Common Stock | Class A Warrant
Initial Public Offering [Abstract]
Class of warrant or right, number of securities called by each warrant or right				1	1
Series B convertible preferred stock | Preferred Stock
Common Stock
Number of shares available under warrant (in shares)											625,208
Initial Public Offering [Abstract]
Exercise price per share (in dollars per share) | $ / shares											$ 0.2999
Maximum | Capital Unit
Underwriter's Unit Purchase Option [Abstract]
Number of units available under the option					40,000
Private Placement
Common Stock
Proceeds from issuance or sale of equity | $		$ 4,650,000
Number of shares available under warrant (in shares)		14,285,714
Convertible preferred stock conversion price (in dollars per share) | $ / shares		$ 0.35
Initial Public Offering [Abstract]
Exercise price per share (in dollars per share) | $ / shares		$ 0.40
Gross proceeds | $		$ 5,000,000
Private Placement | Common stock
Common Stock
Percentage of outstanding shares issued		19.99%
Convertible preferred stock shares authorized (in shares)		11,940,000
Initial Public Offering [Abstract]
Issuance of stock (in shares)		2,345,714
Private Placement | Series A Preferred Stock | Preferred Stock
Common Stock
Preferred stock, shares authorized (in shares)		4,179
Preferred stock, par value per share (in dollars per share) | $ / shares		$ 1,000
IPO | Class B Warrant
Initial Public Offering [Abstract]
Class of warrant or right, number of securities called by each warrant or right					0.5
Common Stock Purchase Agreement | Aspire Capital Fund LLC (Aspire Capital)
Initial Public Offering [Abstract]
Gross proceeds | $			$ 1,000,000			$ 789,000
Underwriter's Unit Purchase Option [Abstract]
Maximum value of common stock purchases committed to by counterparty | $			$ 15,000,000
Number of shares sold under purchase agreement (in shares)			250,000				965,165
Price per share (in dollars per share) | $ / shares			$ 4.00
Proceeds from issuance of common stock | $								$ 1,900,000
Common Stock Purchase Agreement | Maximum | Aspire Capital Fund LLC (Aspire Capital)
Underwriter's Unit Purchase Option [Abstract]
Number of common stock issued per day on achieving threshold price per common stock			50,000
Equity Distribution Agreement for Sale of Common Stock | Maxim Group LLC (Maxim)
Underwriter's Unit Purchase Option [Abstract]
Proceeds from issuance of common stock | $							$ 905,000
Payments of stock issuance costs | $							$ 33,000
Sale of common stock through equity distribution agreement | $										$ 12,075,338
Equity Distribution Agreement for Sale of Common Stock | Maxim Group LLC (Maxim) | Common stock
Initial Public Offering [Abstract]
Issuance of stock (in shares)							1,336,433
Equity Distribution Agreement for Sale of Common Stock | Common Stock | Maxim Group LLC (Maxim)
Underwriter's Unit Purchase Option [Abstract]
Shares available to be issued | $							$ 2,900,000
Over-Allotment Option | Common Stock | Class B Warrant
Initial Public Offering [Abstract]
Class of warrant or right, number of securities called by each warrant or right				0.5
TRx
Common Stock
Contingent shares issuable as part of acquisition (in shares)	2,349,968
Unregistered shares of common stock issued or issuable as part of acquisition | $	$ 8,100,000
Shares issued upon closing (in shares)	5,184,920