Restricted Stock Units - Summary of Restricted Stock Unit Activity (Detail) - Nonvested Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Weighted average number of shares used in computing net loss per common share:
Number of Warrant Shares, Outstanding Beginning balance (in shares)	382,098	338,055
Granted (in shares)	192,987	170,403
Vested (in shares)	(85,153)	(123,539)
Forfeited (in shares)	(46,005)	(2,821)
Number of Warrant Shares, Outstanding Ending balance (in shares)		382,098
Weighted Average Grant Date Fair Value
Unvested beginning balance (in dollars per share)	$ 20.24	$ 14.95
Granted (in dollars per share)	31.42	28.66
Vested (in dollars per share)	25.98	17.44
Forfeited (in dollars per share)	21.38	17.71
Unvested ending balance (in dollars per share)	$ 23.88	$ 20.24