Warrants - Narrative (Details) $ / shares in Units, $ in Thousands				1 Months Ended				3 Months Ended
	May 31, 2018 $ / shares shares	May 29, 2018 $ / shares shares	Dec. 08, 2017 $ / shares shares	Jul. 31, 2018 $ / shares shares	May 31, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares	Mar. 31, 2017 $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) shares	Dec. 31, 2018 $ / shares shares	Jan. 06, 2018 $ / shares shares	Dec. 07, 2017 $ / shares shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)								7,392,966		7,392,966
Warrant exercise price (in dollars per share) | $ / shares								$ 7.36		$ 7.36
Dividend yield
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Anticipated dividend rate								0
Issued in December 2017 Offering - pre-funded warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)						1,184,442			1,184,442			1,184,442
Issued in December 2017 Offering - common warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)			82,118			82,118					409,091	2,727,273
Issued in 2017 Series A Preferred Stock Offering
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant exercise price (in dollars per share) | $ / shares							$ 12.69
Exercise period							5 years
Warrants issued to purchase common stock (in shares)							687,468
Period after date of issuance to be exercised							6 months
Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)								6,187,126		6,187,126
Warrant | Issued in July 2018 Private Placement - common warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)				958,152				958,152		958,152
Warrant exercise price (in dollars per share) | $ / shares				$ 2.70				$ 2.70
Exercise period				5 years 6 months
Warrant | Issued in July 2018 - underwriter warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)				103,186				103,186		103,186
Warrant exercise price (in dollars per share) | $ / shares				$ 3.464				$ 3.464
Warrant | Issued in May 2018 Private Placement - common warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)	1,528,668	1,528,668			1,528,668
Warrant exercise price (in dollars per share) | $ / shares	$ 2.86	$ 2.86			$ 2.86
Exercise period		5 years 6 months			5 years 6 months
Warrant | Issued in May 2018 - underwriter warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)	142,676				142,676			142,676		142,676
Warrant exercise price (in dollars per share) | $ / shares	$ 3.679				$ 3.679			$ 3.679
Exercise period	5 years
Warrant | Issued in December 2017 Offering - pre-funded warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant exercise price (in dollars per share) | $ / shares								$ 0.05
Warrant | Issued in December 2017 Offering - common warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)						2,809,404		2,679,702		2,679,702
Warrant exercise price (in dollars per share) | $ / shares						$ 3.85		$ 3.85			$ 3.85	$ 3.85
Exercise period						5 years		5 years
Warrant | Issued in December 2017 Offering - underwriter warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)			87,274			87,274		87,274		87,274
Warrant exercise price (in dollars per share) | $ / shares			$ 4.8125			$ 4.8125		$ 4.8125
Exercise period			5 years			5 years
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)								687,468		687,468
Warrant exercise price (in dollars per share) | $ / shares								$ 12.69
Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of warrants (shares)								1,205,840		1,205,840
Warrant | Dividend yield
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Anticipated dividend rate								0		0
Warrant | Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-cash income (expense) | $								$ 30	$ (200)