Stock-Based Compensation - Summary of Stock Option Activity Under Plans (Details)	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Subject to Outstanding Options, Beginning Balance | shares	2,141,868
Shares Subject to Outstanding Options, granted | shares	1,340,475
Shares Subject to Outstanding Options, exercised | shares	(15,281)
Shares Subject to Outstanding Options, canceled | shares	(134,920)
Shares Subject to Outstanding Options, Ending Balance | shares	3,332,142
Weighted Average Exercise Price Per Share, Beginning Balance | $ / shares	$ 6.42
Weighted Average Exercise Price Per Share, granted | $ / shares	12.49
Weighted Average Exercise Price Per Share, exercised | $ / shares	1.66
Weighted Average Exercise Price Per Share, cancelled | $ / shares	10.01
Weighted Average Exercise Price Per Share, Ending Balance | $ / shares	$ 8.74