Subsequent Events (Details)							12 Months Ended
	Feb. 13, 2020 shares	Feb. 01, 2020 $ / shares shares	Jan. 06, 2020 $ / shares shares	Jul. 31, 2019 $ / shares shares	Aug. 08, 2018 $ / shares shares	Jun. 05, 2017 shares	Dec. 31, 2019 employee shares	Dec. 31, 2018 $ / shares shares	Apr. 01, 2020 employee	Feb. 29, 2020 USD ($)	Feb. 19, 2020 USD ($)	Jan. 31, 2020 USD ($)	Aug. 30, 2019 USD ($)	Apr. 29, 2019 USD ($)
Subsequent Event [Line Items]
Additional awards to be granted under the plan (in shares) | shares								0
Number of employees | employee							42
Number of options granted to employees (in shares) | shares							658,030	727,257
National Institutes of Health
Subsequent Event [Line Items]
Amount awarded from government grant | $													$ 223,000
CEO
Subsequent Event [Line Items]
Employment agreement, number of SARs granted on a contingent basis (in shares) | shares					1,000,000
Stock Appreciation Rights (SARs)
Subsequent Event [Line Items]
SAR exercise price (in USD per share) | $ / shares				$ 3.8	$ 3.8			$ 3.8
Closing sale price of common stock (in usd per share) | $ / shares				$ 2.66				$ 0.83
Reedy Creek Investments LLC
Subsequent Event [Line Items]
Additional funding potentially receivable | $														$ 10,000,000
2016 Stock Plan
Subsequent Event [Line Items]
Additional awards to be granted under the plan (in shares) | shares				1,000,000		1,200,000
Subsequent event
Subsequent Event [Line Items]
Additional awards to be granted under the plan (in shares) | shares		1,000,000
Closing sale price of common stock (in usd per share) | $ / shares		$ 0.52
Number of employees | employee									28
Market value of listed securities, minimum requirement | $											$ 50,000,000.0
Bid price of common stock, minimum requirement | $											$ 1.00
Subsequent event | National Institutes of Health
Subsequent Event [Line Items]
Amount awarded from government grant | $										$ 1,000,000
Additional amount awarded from government grant | $										$ 500,000
Subsequent event | Stock Appreciation Rights (SARs)
Subsequent Event [Line Items]
Employment agreement, number of SARs granted on a contingent basis (in shares) | shares			600,000
SAR exercise price (in USD per share) | $ / shares			$ 0.82
Subsequent event | Reedy Creek Investments LLC
Subsequent Event [Line Items]
Royalty and milestone agreement funding, amount not expected to be received | $												$ 10,000,000
Subsequent event | 2016 Stock Plan
Subsequent Event [Line Items]
Number of options granted to employees (in shares) | shares	383,000