Subsequent Events - Additional Information (Detail) - Common Class A [Member] - USD ($)	May 01, 2018	Mar. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Common stock, par value		$ 0.001	$ 0.001
Subsequent Events [Member]
Subsequent Event [Line Items]
Common stock, par value	$ 0.001
Maximum [Member] | Subsequent Events [Member]
Subsequent Event [Line Items]
Aggregate offering price of common stock issuable	$ 400,000