Equity - Common Stock (Details) $ / shares in Units, $ in Millions					3 Months Ended	12 Months Ended
	Jan. 06, 2018 $ / shares shares	Dec. 11, 2017 USD ($)	Dec. 07, 2017 $ / shares shares	Mar. 10, 2017 $ / shares	Mar. 31, 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				0.3333
Common stock, par value (in dollars per share) | $ / shares				$ 0.001	$ 0.001	$ 0.001
Sale of common stock (shares)	2,045,454
Number of warrants (shares)					24,848,061	27,264,165
Common stock purchased with warrant (shares)			1
Purchase price (in usd per share) | $ / shares	$ 0.76
Warrant exercise price (in dollars per share) | $ / shares					$ 2.48	$ 2.26
Proceeds from common stock offering, net | $		$ 9.3
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 Common Stock Offering - pre-funded warrants
Class of Stock [Line Items]
Number of warrants (shares)			5,922,208		5,922,208	5,922,208
Issued in December 2017 Common Stock Offering - common warrants
Class of Stock [Line Items]
Number of warrants (shares)	2,045,454		13,636,364				410,586
Purchase price (in usd per share) | $ / shares	$ 0.01
Warrant
Class of Stock [Line Items]
Number of warrants (shares)					17,920,648	20,336,752
Warrant | Issued in December 2017 Common Stock Offering - pre-funded warrants
Class of Stock [Line Items]
Number of warrants (shares)					0	2,416,104
Warrant exercise price (in dollars per share) | $ / shares					$ 0.01
Warrant | Issued in December 2017 Common Stock Offering - common warrants
Class of Stock [Line Items]
Number of warrants (shares)					14,046,950	14,046,950
Warrant exercise price (in dollars per share) | $ / shares	$ 0.77		$ 0.77		$ 0.77	$ 0.77
Warrant exercise period					5 years	5 years
Warrant | Issued in December 2017 Common Stock Offering - underwriter warrants
Class of Stock [Line Items]
Number of warrants (shares)					436,364	436,364
Warrant exercise price (in dollars per share) | $ / shares					$ 0.9625	$ 0.9625
Warrant exercise period					5 years	5 years
Public Stock Offering
Class of Stock [Line Items]
Sale of common stock (shares)			7,714,156