Summary of PSO Activities (Detail) - Performance Stock Options (PSOs) - 2013 Equity Incentive Plan	3 Months Ended
	Mar. 31, 2019 $ / shares shares
Shares Subject to Outstanding PSOs
Beginning balance | shares	143,335
Options granted | shares	490,986
Options exercised | shares	(10,000)
Ending balance | shares	624,321
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 23.76
Options granted | $ / shares	33.29
Options exercised | $ / shares	23.76
Ending balance | $ / shares	$ 31.25