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	$ (48,882)	$ (59,176)	$ (26,331)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	4,551	3,578	2,642
Stock-based compensation	50,964	37,273	22,494
Amortization of acquired intangibles	1,408	1,269	0
Amortization of premiums/accretion of discounts on short-term investments	496	416	639
Allowance for doubtful debts	(1,223)	195	2
Excess tax benefits from share-based compensation	(165)	(385)	0
Changes in operating assets and liabilities:
Accounts receivable, net	(14,828)	(2,805)	(8,868)
Inventory	(1,056)	253	(184)
Prepaid expenses and other assets	(4,220)	409	(1,161)
Accounts payable	977	1,150	159
Accrued compensation and benefits	4,510	2,630	3,672
Accrued and other liabilities	3,242	1,847	(206)
Severance pay (net)	16	93	(32)
Deferred revenue	25,482	18,123	16,761
Deferred tax assets	149	(354)	214
Net cash provided by operating activities	23,867	4,126	9,797
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales/maturities of short-term investments	(89,626)	29,821	42,162
Purchase of short-term investments	33,948	(33,267)	(38,021)
Acquisitions, net of cash acquired	0	(12,083)	0
Net purchases of property and equipment	(8,080)	(5,621)	(2,602)
Change in restricted cash	(17)	(441)	58
Net cash (used in) provided by investing activities	(63,775)	(21,591)	1,597
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from follow-on public offering, net of offering costs	127,853	0	0
Proceeds from issuance of common stock, net of repurchases	23,524	10,546	7,568
Shares withheld for tax withholding on vesting of restricted stock units	(11,464)	(2,074)	(1,252)
Excess tax benefits from share-based compensation	165	385	0
Net cash provided by financing activities	140,078	8,857	6,316
Effect of exchange rate changes on cash and cash equivalents	(14)	0	(207)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	100,156	(8,608)	17,503
CASH AND CASH EQUIVALENTS - Beginning of period	68,096	76,704	59,201
CASH AND CASH EQUIVALENTS - End of period	168,252	68,096	76,704
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	652	287	835
NONCASH INVESTING AND FINANCING ACTIVITIES:
Common stock issued related to acquisitions of businesses	0	24,163	0
Property and equipment incurred but not yet paid	517	820	0
Vesting of restricted and early exercised stock options	$ 767	$ 454	$ 801