Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (21,283)	$ (19,398)	$ (7,475)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	1,615	1,285	796
Stock-based compensation	7,794	4,664	1,788
Capital gain from disposal of fixed assets	$ (4)	(10)	(5)
Amortization of deferred charges related to loan		$ 187	200
Revaluation of fair value of warrants to convertible preferred stock			1,508
Changes in assets and liabilities:
Trade receivables	$ (9,567)	$ (9,601)	(8,233)
Prepaid expenses and other current assets	796	19	19
Trade payables	(91)	540	267
Accrued expenses and other short term liabilities	6,270	5,541	3,460
Severance pay, net	79	348	377
Deferred revenues	11,554	8,517	7,427
Other long term liabilities	108	798	(75)
Net cash provided by (used in) operating activities	(2,729)	(7,110)	54
Cash flows from investing activities:
Increase in short-term deposits	(22,001)	(30,758)	(4,001)
Decrease (increase) in long-term deposits	11	39	(28)
Decrease (increase) in restricted cash	(156)	$ 230	$ (338)
Proceeds from sale of property and equipment	4
Purchase of property and equipment	(4,536)	$ (2,333)	$ (1,349)
Net cash used in investing activities	(26,678)	(32,822)	(5,716)
Cash flows from financing activities:
Exercise of employee stock options	$ 2,055	$ 382	127
Exercise of warrants to purchase Series D convertible preferred stock			1,137
Payment of deferred equity offering cost		$ (1,937)	$ (439)
Net proceeds from initial public offering		108,447
Net cash provided by financing activities	$ 2,055	106,892	$ 825
Increase (decrease) in cash and cash equivalents	(27,352)	66,960	(4,837)
Cash and cash equivalents at beginning of period	76,593	9,633	14,470
Cash and cash equivalents at end of period	49,241	76,593	$ 9,633
Supplemental disclosures of non-cash flow information
Deferred rent fixed asset additions	$ 1,355	1,071
Conversion of preferred stock to common stock		43,775
Conversion of liability warrants to equity		$ 2,866
Deferred charges related to warrants granted to credit facilitator			$ 263
Exercise of warrants to purchase Series D convertible preferred stock			4,679
Supplemental disclosure of cash flow information:
Cash paid for income taxes	$ 354	$ 304	$ 227