Equity - Summary of Stock Option Activity (Detail)	6 Months Ended
	Jun. 30, 2018 $ / shares shares
Number of shares
Stock options, beginning balance (in shares) | shares	6,342,526
Stock options, granted (in shares) | shares	2,168,602
Stock options, exercised (in shares) | shares	1,030,576
Stock options, canceled or expired (in shares) | shares	25,498
Stock options, ending balance (in shares) | shares	7,455,054
Stock options, exercisable, ending balance (in shares) | shares	2,958,222
Weighted average price
Weighted average exercise price, beginning balance (in dollars per share) | $ / shares	$ 6.51
Weighted average exercise price, granted (in dollars per share) | $ / shares	8.34
Weighted average exercise price, exercised (in dollars per share) | $ / shares	5.53
Weighted average exercise price, canceled or expired (in dollars per share) | $ / shares	8.72
Weighted average exercise price, ending balance (in dollars per share) | $ / shares	7.18
Weighted average exercise price, exercisable, ending balance (in dollars per share) | $ / shares	$ 6.14