Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2016

Accounting Policies [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	As of September 30,
	2015	2016
Outstanding common stock options	5,693,156	6,544,738
Outstanding warrants	34,647	34,647
Outstanding PRSUs	216,008	—
Outstanding RSUs	352,949	414,018
Shares to be purchased under the ESPP	23,352	34,853
Total	6,320,112	7,028,256