Stockholders' Equity and Stock-Based Compensation Expense - Equity (Details) $ / shares in Units, $ in Millions					1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 11, 2020 USD ($) shares	Apr. 22, 2020 USD ($) shares	Apr. 12, 2020 director item $ / shares shares	Oct. 21, 2019 shares	Oct. 31, 2019 USD ($) item $ / shares shares	Jun. 30, 2020 $ / shares shares	Jun. 30, 2020 $ / shares shares	Dec. 31, 2019 $ / shares shares
Common Stock
Common stock par value (in dollar per share) | $ / shares						$ 0.001	$ 0.001	$ 0.001
Warrants to purchase common stock						14,000,000	14,000,000
April 22, 2025 Expiration Date
Common Stock
Warrants to purchase common stock						1,322,510	1,322,510
Warrant exercise price | $ / shares						$ 2.50	$ 2.50
June 11, 2025 Expiration Date
Common Stock
Warrants to purchase common stock						12,677,490	12,677,490
Warrant exercise price | $ / shares						$ 2.50	$ 2.50
Securities purchase agreement
Common Stock
Number of days following the days of breach			30 days
Securities purchase agreement | Private Placement
Common Stock
Common stock par value (in dollar per share) | $ / shares			$ 0.001
Price per share | $ / shares			$ 2.50
Number of tranches | item			2
Warrant exercise price | $ / shares			$ 2.50
Securities purchase agreement | Closing of second tranche | Private Placement
Common Stock
Percentage of Outstanding Shares Of Common Stock			51.30%
Securities purchase agreement | Minimum | Closing of first tranche | Private Placement
Common Stock
Shares issued (in shares)		1,322,510
Aggregate purchase price of warrants | $		$ 3.3
Warrants to purchase common stock		1,322,510
Securities purchase agreement | Minimum | Closing of second tranche | Private Placement
Common Stock
Shares issued (in shares)	12,677,490
Aggregate purchase price of warrants | $	$ 31.7
Warrants to purchase common stock	12,677,490
Securities purchase agreement | Maximum | Private Placement
Common Stock
Shares issued (in shares)			14,000,000
Warrants to purchase common stock			14,000,000
Securities purchase agreement | Maximum | Closing of second tranche | Private Placement
Common Stock
Percentage of Outstanding Shares Of Common Stock			67.80%
Investor rights agreement | Scenario 1
Common Stock
Number of directors designated as board of directors | director			2
Investor rights agreement | Scenario 2
Common Stock
Number of directors designated as board of directors | director			1
Investor rights agreement | Minimum | Scenario 1
Common Stock
Percentage of Outstanding Shares Of Common Stock			15.00%
Investor rights agreement | Minimum | Scenario 2
Common Stock
Percentage of Outstanding Shares Of Common Stock			8.00%
Common Stock
Common Stock
Shares issued (in shares)						14,000,000	14,000,000
Aspire
Common Stock
Shares issued (in shares)							0
Maximum amount committed to be purchased | $					$ 20.0
Term over which the purchase can be made					30 months
Threshold triggering closing price per share to issue purchase notice | $ / shares					$ 0.25
Maximum number of shares that can be purchased under purchase notice					50,000
Number of lowest closing sales price | item					3
Number of consecutive business days immediately preceding the purchase date					10 days
Maximum shares sold per business day					2,000,000
Volume-weighted average price notice, percentage of companys common stock					30.00%
Purchase price as a percentage of volume-weighted average price					97.00%
Number of commitment shares issued				104,167
Maximum number of shares sold				2,626,165
Commitment fee percentage				19.99%
Number of commitment shares purchased								50,000