Equity - Common Stock (Details) $ / shares in Units, $ in Millions									1 Months Ended	9 Months Ended	12 Months Ended
	Jul. 05, 2018 USD ($) $ / shares shares	Jul. 02, 2018 $ / shares shares	May 31, 2018 USD ($) $ / shares shares	May 29, 2018 $ / shares shares	May 24, 2018 $ / shares	Jan. 06, 2018 $ / shares shares	Dec. 11, 2017 USD ($)	Dec. 07, 2017 $ / shares shares	May 31, 2018 $ / shares shares	Sep. 30, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares	Dec. 08, 2017 shares	Jul. 31, 2016 shares
Class of Stock [Line Items]
Common stock, shares authorized (shares)										150,000,000	150,000,000
Stock split, conversion ratio					0.2
Common stock, par value (in dollars per share) | $ / shares		$ 0.001			$ 0.001					$ 0.001	$ 0.001
Sale of common stock (shares)						409,091
Number of warrants (shares)										7,497,642	5,452,923
Common stock purchased with warrant (shares)								1
Warrant exercise price (in dollars per share) | $ / shares										$ 8.83	$ 11.32
Period to exercise options								30 days
Purchase price (in usd per share) | $ / shares						$ 3.80
Proceeds from common stock offering, net | $			$ 5.3				$ 9.3
Percentage of aggregate shares of common stock available for purchase			7.00%
Minimum
Class of Stock [Line Items]
Common stock, shares authorized (shares)													100,000,000
Maximum
Class of Stock [Line Items]
Common stock, shares authorized (shares)													150,000,000
Issued in December 2017 Offering - pre-funded warrants
Class of Stock [Line Items]
Number of warrants (shares)								1,184,442		1,184,442	1,184,442
Issued in December 2017 Offering - common warrants
Class of Stock [Line Items]
Number of warrants (shares)						409,091		2,727,273			82,118	82,118
Purchase price (in usd per share) | $ / shares						$ 0.01
Warrant
Class of Stock [Line Items]
Number of warrants (shares)										6,187,126	4,067,367
Warrant | Issued in December 2017 Offering - pre-funded warrants
Class of Stock [Line Items]
Number of warrants (shares)										0	483,221
Warrant exercise price (in dollars per share) | $ / shares										$ 0.05
Warrant | Issued in December 2017 Offering - common warrants
Class of Stock [Line Items]
Number of warrants (shares)										2,679,702	2,809,404
Warrant exercise price (in dollars per share) | $ / shares						$ 3.85		$ 3.85		$ 3.85	$ 3.85
Warrant exercise period										5 years	5 years
Warrant | Issued in December 2017 Offering - underwriter warrants
Class of Stock [Line Items]
Number of warrants (shares)										87,274	87,274
Warrant exercise price (in dollars per share) | $ / shares										$ 4.8125	$ 4.8125
Warrant exercise period										5 years	5 years
Warrant | Issued in May 2018 Private Placement - common warrants
Class of Stock [Line Items]
Number of warrants (shares)			1,528,668						1,528,668
Warrant exercise price (in dollars per share) | $ / shares			$ 2.86						$ 2.86
Purchase price (in usd per share) | $ / shares				$ 0.125
Warrant exercise period				5 years 6 months					5 years 6 months
Warrant | Issued in July 2018 - underwriter warrants
Class of Stock [Line Items]
Number of warrants (shares)			142,676						142,676	142,676	0
Warrant exercise price (in dollars per share) | $ / shares			$ 3.679						$ 3.679	$ 3.679
Warrant exercise period			5 years
Warrant | Warrants Issued in July 2018 Private Placement
Class of Stock [Line Items]
Number of warrants (shares)		958,152
Warrant exercise price (in dollars per share) | $ / shares	$ 3.464	$ 2.70
Purchase price (in usd per share) | $ / shares		$ 0.125
Warrant exercise period	5 years	5 years 6 months
Warrants to purchase shares of common stock (in shares)	103,186
Public Stock Offering
Class of Stock [Line Items]
Sale of common stock (shares)								1,542,832
May 2018 Purchase Agreement
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares				$ 0.001
Sale of common stock (shares)				2,038,224
Purchase price (in usd per share) | $ / shares				$ 2.85
Percentage of shares of common stock sold				75.00%
July 2018 Purchase Agreement
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares		$ 2.69
Sale of common stock (shares)		1,474,080
Proceeds from common stock offering, net | $	$ 3.6
Percentage of shares of common stock sold		65.00%