Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Detail)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of shares, Issued and unvested beginning balance	276,301
Number of shares, Vested	(123,026)
Number of shares, Forfeited, cancelled or expired	0
Number of shares, Issued and unvested ending balance	153,275
Weighted average grant date fair value, Issued and unvested, beginning balance | $ / shares	$ 0.42
Weighted average grant date fair value, Vested | $ / shares	0.42
Weighted average grant date fair value, Issued and unvested, ending balance | $ / shares	$ 0.42