Stock-based Compensation Expense - Summary of Restricted Stock Activity outside of 2019 and 2016 Plan (Details) - Grants Outside of 2016 Stock Incentive Plan and 2019 Stock Incentive Plan - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvested, Beginning balance	334,647	446,789
Number of Shares, Vested	(291,789)	(112,142)
Number of Shares, Unvested, Ending balance	42,858	334,647
Weighted Average Grant Date Fair Value, Unvested, Beginning balance	$ 2.94	$ 2.94
Weighted Average Grant Date Fair Value, Vested	2.94	2.94
Weighted Average Grant Date Fair Value, Unvested, Ending balance	$ 2.93	$ 2.94