Stock-Based Compensation - Summary of Stock Option Activity (Detail) - Employee Stock Option - 2013 and 2017 Equity Incentive Plan	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Shares Subject to Outstanding Stock Options
Beginning balance (in shares) | shares	7,507,690
Options granted (in shares) | shares	2,199,307
Options exercised (in shares) | shares	(916,157)
Options canceled (in shares) | shares	(1,242,404)
Ending balance (in shares) | shares	7,548,436
Weighted-Average Exercise Price Per Share
Beginning balance (in dollars per share) | $ / shares	$ 33.25
Options granted (in dollars per share) | $ / shares	27.74
Options exercised (in dollars per share) | $ / shares	21.32
Options canceled (in dollars per share) | $ / shares	38.62
Ending balance (in dollars per share) | $ / shares	$ 32.21