Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (17,710)	$ (21,283)	$ (19,398)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	2,180	1,615	1,285
Stock-based compensation	12,938	7,794	4,664
Capital gain from disposal of fixed assets	(2)	(4)	(10)
Amortization of deferred charges related to loan			187
Changes in assets and liabilities:
Trade receivables	(6,425)	(9,567)	(9,601)
Prepaid expenses and other current assets	(1,028)	796	19
Trade payables	(1,324)	(91)	540
Accrued expenses and other short term liabilities	5,302	6,270	5,541
Severance pay	136	79	348
Deferred revenues	13,269	11,554	8,517
Other long term liabilities	11	108	798
Net cash provided by (used in) operating activities	7,347	(2,729)	(7,110)
Cash flows from investing activities:
Increase in short-term deposits	(8,390)	(22,001)	(30,758)
Decrease (increase) in long-term deposits	(111)	11	39
Decrease (increase) in restricted cash	(21)	(156)	230
Proceeds from sale of property and equipment	2	4
Purchase of property and equipment	(3,825)	(4,536)	(2,333)
Net cash used in investing activities	(12,345)	(26,678)	(32,822)
Cash flows from financing activities:
Proceeds from employee stock plans, net	4,072	2,055	382
Payment of deferred equity offering cost			(1,937)
Net proceeds from initial public offering			108,447
Net cash provided by financing activities	4,072	2,055	106,892
Increase (decrease) in cash and cash equivalents	(926)	(27,352)	66,960
Cash and cash equivalents at beginning of period	49,241	76,593	9,633
Cash and cash equivalents at end of period	48,315	49,241	76,593
Supplemental disclosures of non-cash flow information
Deferred rent fixed asset additions	583	1,355	1,071
Conversion of preferred stock to common stock			43,775
Conversion of liability warrants to equity			2,866
Supplemental disclosure of cash flow information:
Cash paid for income taxes	$ 246	$ 354	$ 304