Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($)			1 Months Ended		4 Months Ended	12 Months Ended
	Aug. 30, 2019	Jan. 09, 2018	Aug. 31, 2019	Apr. 30, 2016	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Sep. 16, 2019	Aug. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Class of Stock [Line Items]
Capital stock, shares authorized (in shares)					210,000,000	210,000,000
Common stock, shares authorized (in shares)					200,000,000	200,000,000	200,000,000
Common stock, par value (in USD per share)					$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001			$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)					10,000,000	10,000,000	10,000,000
Preferred stock, par value (in USD per share)					$ 0.0001	$ 0.0001
Proceeds from issuance of common stock, net of underwriting fees and commissions						$ 747,000	$ 35,625,000
Shelf registration and public offering, costs capitalized					$ 49,000	$ 49,000	$ 49,000	$ 49,000			$ 49,000	$ 49,000	$ 49,000	$ 49,000	$ 49,000
Fundamental transaction common stock acquired threshold		50.00%
Black Scholes valuation input, historical volatility period		100 days
Maximum volatility rate used to derive Black-Scholes Value in event of fundamental transaction		100.00%
Warrant exercise limitation, maximum beneficial ownership percentage, current		4.99%
Warrant exercise limitation, maximum beneficial ownership percentage, if elected by holder		9.99%
Beneficial ownership percentage, exception to exercise limitation provision		10.00%
Warrants exercised (in shares)						0	0
Common stock, shares outstanding (in shares)					26,734,800	26,734,800	26,056,735
Common stock repurchased (in shares)				9,500
Common stock repurchased, value				$ 155,000
Preferred stock, shares outstanding (in shares)					0	0	0
January 2018 Offering
Class of Stock [Line Items]
Common stock issued during period (in shares)		10,000,000
Price per share (in USD per share)		$ 3.8
Warrant exercise price (in USD per share)		$ 4.66
Warrants expiration period		4 years
Proceeds from issuance of common stock, net of underwriting fees and commissions		$ 35,194,000
Underwriting discounts and commissions and offering expenses		2,806,000
Shelf registration and public offering, costs capitalized		$ 370,000
January 2018 Offering | Maximum
Class of Stock [Line Items]
Warrants issued (in shares)		10,000,000
Shelf Registration
Class of Stock [Line Items]
Shelf registration and public offering, costs capitalized		$ 110,000
Aspire Capital | Common Stock Purchase Agreement
Class of Stock [Line Items]
Maximum value of shares of common stock authorized to be sold	$ 25,000,000
Common stock purchase agreement term	30 months
Common stock registered (in shares)									7,032,630
Maximum shares to be purchased with purchase notice per business day (in shares)	100,000
Maximum aggregate purchase price payable on one purchase date	$ 500,000
Number of shares submitted via purchase notice to trigger a VWAP purchase notice (in shares)	100,000
Maximum percentage of common stock traded on trading day to be purchased	30.00%
Purchase price per share pursuant to VWAP purchase notice as a percentage of VWAP for common stock (in USD per share)	97.00%
Minimum closing sale price to effect purchase of shares (in usd per share)	$ 0.25
Maximum number of shares that may be sold under agreement (in shares)	5,211,339
Percentage of common stock on date of purchase agreement that cannot be exceeded	19.99%
Closing sale price of common stock (in usd per share)										$ 2.17
Shares of common stock issued for commitment fee (in shares)	345,622
Value of commitment fee shares issued			$ 750,000
Common stock issued during period (in shares)					300,000
Average sales price per share of common stock (in usd per share)					$ 2.49
Available for sale under common stock purchase agreement					$ 24,253,000	$ 24,253,000