Stockholders' Equity - Additional Information (Details)	1 Months Ended						12 Months Ended
	Feb. 28, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Oct. 31, 2018 USD ($) $ / shares shares	Apr. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	May 31, 2017 USD ($)	Dec. 31, 2019 USD ($) Vote $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares
Class Of Stock [Line Items]
Shares authorized | shares							510,000,000
Common stock, shares authorized | shares		500,000,000					500,000,000	500,000,000
Preferred stock, shares authorized | shares		10,000,000					10,000,000	10,000,000
Common stock, par value | $ / shares		$ 0.0001					$ 0.0001	$ 0.0001
Preferred stock, par value | $ / shares		$ 0.0001					$ 0.0001	$ 0.0001
Number of common stock holders voting right | Vote							1
Common stock voting rights							Each holder of common stock is entitled to one vote for each share of common stock held
Common stock dividends declared							$ 0	$ 0
Preferred stock, shares outstanding | shares		0					0	0
Proceeds from issuance of common stock in public offering, net								$ 54,048,000	$ 11,380,000
Underwriting discounts and commissions	$ 4,100,000
Offering costs	400,000
Net proceeds from sale of common stock	$ 64,500,000
Reduction in exercise price of each warrant from public offering price for pre-funded warrants per share | $ / shares	$ 0.0001
Maximum ownership percentage for outstanding warrants to purchase shares of common stock to be exercised	4.99%
Period after notice received by company maximum ownership percentage to be effective description							The revised Maximum Ownership Percentage would be effective 61 days after the notice is received by the Company
Proceeds from Warrant Exercises							$ 0
Common Stock
Class Of Stock [Line Items]
Number of shares issued | shares				5,046,510				6,893,000	3,000,000
Public offering price | $ / shares				$ 8.00
Proceeds from issuance of common stock in public offering, net									$ 1,000
Underwriting discounts and commissions				$ 2,400,000
Offering costs				300,000
Follow-on Public Offering | Common Stock
Class Of Stock [Line Items]
Number of shares issued | shares	4,625,000
Public offering price | $ / shares	$ 8.00
Proceeds from issuance of common stock in public offering, net				$ 37,700,000
Public offering price of warrant | $ / shares	$ 7.9999
Follow-on Public Offering | Common Stock | Maximum
Class Of Stock [Line Items]
Warrants to purchase shares | shares	4,000,000
Follow-on Public Offering | Common Stock | JonesTrading Institutional Services LLC
Class Of Stock [Line Items]
Number of shares issued | shares					3,000,000
Public offering price | $ / shares					$ 4.10
Proceeds from issuance of common stock in public offering, net					$ 11,400,000
Underwriting discounts and commissions					600,000
Offering costs					$ 300,000
Underwriters' Over-allotment Option
Class Of Stock [Line Items]
Number of shares issued | shares	1,125,000
Underwriters' Over-allotment Option | Common Stock
Class Of Stock [Line Items]
Number of shares issued | shares				546,510
At-the-Market (ATM) Sales Agreement | JonesTrading Institutional Services LLC
Class Of Stock [Line Items]
Number of shares issued | shares			1,845,820
Public offering price | $ / shares			$ 9.21
Net proceeds from sale of common stock			$ 16,400,000
Aggregate offering price of common stock						$ 20,000,000
Proceeds from issuance of common stock gross			$ 17,000,000
At-the-Market (ATM) Sales Agreement | Jeffries LLC
Class Of Stock [Line Items]
Aggregate offering price of common stock		$ 60,000,000
Common stock remained available for sale							$ 60,000,000