Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Tax provision related to foreign withholding tax	$ 412,500	$ 825,000
Percentage of valuation allowance against deferred tax assets	100.00%	100.00%
Unrecognized tax benefits	$ 1,334,000	$ 972,000	$ 510,000
Federal
Income Taxes [Line Items]
Operating loss carryforwards	$ 85,710,000
Operating loss carryforwards expiration start year	2035
Net operating losses indefinite carryforward amount	$ 57,198,000
State
Income Taxes [Line Items]
Operating loss carryforwards	$ 84,560,000
Operating loss carryforwards expiration start year	2035
Research Tax Credit
Income Taxes [Line Items]
Prepaid amount to be offset against payroll tax liabilities	$ 250,000
Prepaid amount to be offset against payroll tax liabilities remaining from previous year	140,000
Research Tax Credit | Federal
Income Taxes [Line Items]
Unrecognized tax benefits	1,334,000
Tax credits	$ 1,202,000
Tax credits carryforward expiration start year	2035
Research Tax Credit | State
Income Taxes [Line Items]
Unrecognized tax benefits		$ 972,000
Tax credits	$ 1,002,000
Tax credits carryforward expiration start year	2031