Stockholders' Equity (Details) $ / shares in Units, $ in Millions				1 Months Ended		12 Months Ended
	Sep. 11, 2018 shares	May 18, 2018 shares	Jul. 31, 2017 item	Oct. 31, 2018 USD ($) $ / shares shares	Jun. 30, 2018 shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares	Mar. 12, 2018 shares	Mar. 11, 2018 shares
Stockholders’ Equity
Number of voting rights entitled for each share of common stock held | item			1
Reverse stock split ratio		0.0667			0.0667
Common stock, shares authorized		150,000,000						500,000,000	250,000,000
Number of pre-funded warrants issued						2,166,588	106,376
Shares of common stock reserved for issuance
Options issued and outstanding						2,944,148	2,984,304
Options available for grant under stock option plans						162,892	513,385
RSUs awards issued and outstanding						392,904	392,923
Warrants issued and outstanding						2,427,653	443,756
Convertible notes						759,396	1,036,717
Total						6,895,858	5,371,085
Inducement options
Shares of common stock reserved for issuance
Options issued and outstanding						208,865
Blank check preferred stock
Stockholders’ Equity
Common stock, shares authorized					10,000,000
October 2018 Equity Financing
Stockholders’ Equity
Shares issued (in shares)				11,575,001
Purchase price of common stock (as per shares) | $ / shares				$ 0.60
Number of pre-funded warrants issued				3,425,000
Warrants Issued Price Per Share | $ / shares				$ 0.59
Gross proceeds from issuance of common stock | $				$ 9.0
Exercise price (in dollars per share) | $ / shares				$ 0.01
Proceeds from warrant exercise | $				$ 7.2
Common Stock
Stockholders’ Equity
Common stock, shares authorized					210,000,000
Shares issued (in shares)	75,000
Common Stock | Common stock - voting
Stockholders’ Equity
Common stock, shares authorized					150,000,000	150,000,000	250,000,000
Common Stock | Common stock - non-voting
Stockholders’ Equity
Common stock, shares authorized					50,000,000	50,000,000	50,000,000
Common Stock | October 2018 Equity Financing | Common stock - voting
Stockholders’ Equity
Number of pre-funded warrants issued						3,425,000
Convertible non-voting common stock
Stockholders’ Equity
Reverse stock split ratio						1