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Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)		1 Months Ended	9 Months Ended	12 Months Ended
	Oct. 03, 2018	Oct. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Subsidiary Sale Of Stock [Line Items]
Unrecognized tax benefits			$ 10,800,000
Interest expense or penalties related to unrecognized tax benefits			$ 0
Corporate tax rate			21.00%	35.00%
Tax cuts and jobs act of 2017 reduced percentage of taxable income for net operating loss			80.00%
Subsequent Event \| IPO
Subsidiary Sale Of Stock [Line Items]
Aggregate net proceeds from common stock	$ 109,400,000
Subsequent Event \| Common Stock \| IPO
Subsidiary Sale Of Stock [Line Items]
Number of shares issued and sold	7,840,908	7,840,908
Underwriters option to purchase additional shares	1,022,727
Shares issued, price per share	$ 15.00	$ 15.00
Subsequent Event \| Common Stock \| Selling Stockholders
Subsidiary Sale Of Stock [Line Items]
Number of shares issued and sold	6,507,288
Underwriters option to purchase additional shares	848,776