Fair Value of Financial Instruments - Summary of Fair Value Maturities for Financial Asset (Detail) $ in Thousands	Sep. 30, 2017 USD ($)
Fair Value Disclosures [Abstract]
Cash equivalents and marketable securities, Maturities by Period, Total	$ 59,808
Cash equivalents and marketable securities, Maturities by Period, Less than 1 year	59,808
Cash equivalents and marketable securities, Maturities by Period, 1-5 years	0
Cash equivalents and marketable securities, Maturities by Period, 5-10 years	0
Cash equivalents and marketable securities, Maturities by Period, More than 10 years	$ 0