Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Schedule of common stock equivalents excluded due to anti-dilutive effect

	As of March 31,
	2017	2018
Outstanding common stock options	6,860,968	5,996,771
Outstanding warrants	34,647	722,000
Outstanding RSUs	616,912	1,524,581
Shares to be purchased under the ESPP	30,121	20,456
Total	7,542,648	8,263,808