Fair Value of Financial Instruments - Company's Financial Instruments Carried at Fair Value Using Lowest Level of Input (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 41	$ 8,299
Total assets	41	8,299
Quoted Prices in Active Markets for Identical Items (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	41	8,299
Total assets	$ 41	$ 8,299