Stock Option Plans - Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Number of Shares
Beginning balance (shares) | shares	2,900,676
Options granted (shares) | shares	1,809,400
Options exercised (shares) | shares	(938,456)
Options cancelled (shares) | shares	(5,526)
Ending balance (shares) | shares	3,766,094
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 2.66
Options granted (in dollars per share)	21.47
Options exercised (in dollars per share)	0.95
Options cancelled (in dollars per share)	11.14
Ending balance (in dollars per share)	12.11
Weighted average grant date fair value of employee stock options granted (in dollars per share)	$ 9.69