Warrants - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Jan. 06, 2018	Dec. 08, 2017	Dec. 07, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		24,848,061		27,264,165
Warrant exercise price (in dollars per share)		$ 2.48		$ 2.26
Anticipated dividend rate		0.00%
Proceeds from Series A preferred stock offering allocated to warrants		$ 0	$ 7,886
Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		6,927,413		6,927,413
Anticipated dividend rate		0.00%		0.00%
Warrant | Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-cash income (expense)		$ 200	$ (100)
Issued in 2017 Series A Preferred Stock Offering
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued to purchase common stock (in shares)	3,437,334		3,437,334
Warrant exercise price (in dollars per share)	$ 2.54		$ 2.54
Period after date of issuance to be exercised	6 months
Exercise period	5 years
Issued in December 2017 Common Stock Offering - pre-funded warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		5,922,208		5,922,208			5,922,208
Issued in December 2017 Common Stock Offering - common warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)					2,045,454	410,586	13,636,364
Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		17,920,648		20,336,752
Warrant | Issued in 2017 Series A Preferred Stock Offering
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		3,437,334		3,437,334
Warrant exercise price (in dollars per share)		$ 2.537730
Warrant | Issued in December 2017 Common Stock Offering - pre-funded warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		0		2,416,104
Warrant exercise price (in dollars per share)		$ 0.01
Warrant | Issued in December 2017 Common Stock Offering - common warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		14,046,950		14,046,950
Warrant exercise price (in dollars per share)		$ 0.77		$ 0.77	$ 0.77		$ 0.77
Exercise period		5 years		5 years
Warrant | Issued in December 2017 Common Stock Offering - underwriter warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)		436,364		436,364
Warrant exercise price (in dollars per share)		$ 0.9625		$ 0.9625
Exercise period		5 years		5 years