Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (13,694)	$ (17,710)	$ (21,283)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	3,328	2,180	1,615
Stock-based compensation	19,835	12,938	7,794
Capital gain from disposal of fixed assets	(20)	(2)	(4)
Changes in assets and liabilities:
Trade receivables	(21,735)	(6,425)	(9,567)
Prepaid expenses and other current assets	(3,317)	(1,028)	796
Trade payables	(653)	(1,324)	(91)
Accrued expenses and other short term liabilities	14,453	5,302	6,270
Deferred revenues	18,885	13,269	11,554
Other long term liabilities	(731)	147	187
Net cash provided by (used in) operating activities	16,351	7,347	(2,729)
Cash flows from investing activities:
Increase in short-term investments	(14,402)	(8,390)	(22,001)
Decrease (increase) in long-term deposits	(305)	(111)	11
Proceeds from sale of property and equipment	20	2	4
Purchase of property and equipment	(5,314)	(3,825)	(4,536)
Net cash used in investing activities	(20,001)	(12,324)	(26,522)
Cash flows from financing activities:
Proceeds from employee stock plans, net	12,083	4,072	2,055
Net cash provided by financing activities	12,083	4,072	2,055
Increase (decrease) in cash, cash equivalents and restricted cash	8,433	(905)	(27,196)
Cash, cash equivalents and restricted cash at beginning of period	48,803	49,708	76,904
Cash, cash equivalents and restricted cash at end of period	57,236	48,803	49,708
Supplemental disclosures of non-cash flow information
Deferred rent fixed asset additions		583	1,355
Supplemental disclosure of cash flow information:
Cash paid for income taxes	$ 285	$ 246	$ 354