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Stockholders' Equity - Common Stock (Details) - USD ($)				1 Months Ended	3 Months Ended							9 Months Ended		16 Months Ended
	Sep. 21, 2018	Jul. 25, 2018	Jun. 01, 2018	Oct. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	May 24, 2018	May 23, 2018
Common Stock [Abstract]
Common stock issued (in shares)		6,723
Number of shares callable by warrants (in shares)					50							50		50	2,300,000	23,400,000
Exercise of warrants					490
Proceeds from sale of common stock, net of offering cost												$ 15,964,000	$ 6,246,000
Common stock issued, value						$ 64,000	$ 1,873,000		$ 3,686,000	$ (297,000)	$ 27,000
Series U Warrants [Member]
Common Stock [Abstract]
Common stock issued (in shares)												3,450,000
Sale of Stock, Price Per Share					$ 5.00							$ 5.00		$ 5.00
Warrants expected term					5 years							5 years		5 years
Common Stock [Member]
Common Stock [Abstract]
Common stock issued (in shares)		6,723				5,000	139,855		29,407	192	202
Number of shares callable by warrants (in shares)		141,183
Exercise of warrants				1,039,000								1,672,000
Warrants expected term					5 years							5 years		5 years
Warrant exercise price		$ 39.93
Common Stock [Member] | B. Riley FBR [Member] | Sales Agreement [Member]
Common Stock [Abstract]
Remaining availability under financing facility					$ 0							$ 0		$ 0
Common Stock [Member] | B. Riley FBR [Member] | Sales Agreement [Member] | Maximum [Member]
Common Stock [Abstract]
Proceeds from sale of common stock, net of offering cost			$ 6,500,000
Common Stock [Member] | B. Riley FBR [Member] | ATM Program [Member] | Sales Agreement [Member]
Common Stock [Abstract]
Common stock issued (in shares)														200,000
Proceeds from sale of common stock, net of offering cost														$ 3,800,000
Remaining availability under financing facility					$ 0							$ 0		$ 0
Common Stock [Member] | B. Riley FBR [Member] | ATM Program [Member] | Sales Agreement [Member] | Maximum [Member]
Common Stock [Abstract]
Proceeds from sale of common stock, net of offering cost			$ 6,500,000
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member]
Common Stock [Abstract]
Common stock issued (in shares)												32,170
Proceeds from sale of common stock, net of offering cost												$ 300,000
Common stock issued, value	$ 5,000,000
Period exercisable from the date of issuance	24 months
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Securities Purchase Agreement [Member]
Common Stock [Abstract]
Trading Volume of Common Shares	0
Upper Limit on the Price Per Share	$ 0
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Maximum [Member]
Common Stock [Abstract]
Remaining availability under financing facility	$ 100,000
Beneficial ownership percentage of common stock outstanding	4.99%
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Maximum [Member] | Single Regular Purchase [Member]
Common Stock [Abstract]
Common stock issued (in shares)	5,000
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Minimum [Member] | Single Regular Purchase [Member]
Common Stock [Abstract]
Common stock issued, value	$ 1,000,000
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Purchase Agreement [Member]
Common Stock [Abstract]
Common stock issued (in shares)								12,802
Proceeds from sale of common stock, net of offering cost								$ 300,000
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Purchase Agreement [Member] | Maximum [Member]
Common Stock [Abstract]
Floor price of per share	$ 12.50
Series U Warrants [Member]
Common Stock [Abstract]
Number of shares callable by warrants (in shares)					75,000							75,000		75,000
Warrant exercise price					$ 6.25							$ 6.25		$ 6.25
Common Class A [Member]
Common Stock [Abstract]
Common stock issued (in shares)												289,000
Common Class B [Member]
Common Stock [Abstract]
Number of shares callable by warrants (in shares)					2,711,000							2,711,000		2,711,000

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