CONDENSED 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	$ (84,482)	$ (61,889)	$ (32,497)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	28,791	16,749	8,467
Depreciation	2,757	2,215	1,563
Amortization of intangible assets	870	1,430	485
Provision for doubtful accounts	150	54	(67)
Impairment of in-process research and development			3,925
Loss on disposal of equipment		21
Amortization of premium on investment securities	368
Changes in operating assets and liabilities:
Accounts receivable	(8,148)	(10,605)	(5,996)
Other current and noncurrent assets	(932)	(835)	(2,713)
Accounts payable	1,414	(12)	147
Accrued expenses and other long-term liabilities	(5,024)	2,881	5,884
Deferred revenue	15,701	13,422	(4,748)
Net cash used in operating activities	(48,535)	(36,569)	(25,550)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(3,730)	(3,119)	(2,244)
Purchase of investment securities	(60,913)	(36,104)
Proceeds from maturities of investment securities	44,964
Purchase of Push Computing, Inc. - net of cash acquired			(333)
Purchase of intellectual property		(650)	(30)
Net cash used in investing activities	(19,679)	(39,873)	(2,607)
CASH FLOWS FROM FINANCING ACTIVITIES:
Amount drawn from revolving line of credit		3,300	4,300
Repayments of revolving line of credit		(7,600)
Proceeds from the issuance of convertible preferred stock-net of cash issuance costs		1,994	57,707
Proceeds from initial public offering		106,950
Payment of offering costs related to initial public offering		(4,076)
Proceeds from Employee Stock Purchase Plan	5,406	4,280
Proceeds from exercise of stock options	5,755	2,308	1,031
Net cash provided by financing activities	11,161	107,156	63,038
NET CHANGE IN CASH AND CASH EQUIVALENTS	(57,053)	30,714	34,881
CASH AND CASH EQUIVALENTS-Beginning of period	104,287	73,573	38,692
CASH AND CASH EQUIVALENTS-End of period	47,234	104,287	73,573
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	595	271	$ 168
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING ACTIVITIES RELATED TO ACQUISITIONS
Fair value of assets acquired		2,276
Liabilities assumed		(294)
Issuance of stock		(1,982)
SUPPLEMENTAL DISCLOSURES OF NONCASH FINANCING ACTIVITIES:
Issuance of common stock pursuant to the Employee Stock Purchase Plan	7,359
Purchase of property and equipment recorded in accounts payable	554
Tenant improvement allowance recorded in property and equipment and liabilities	$ 1,068
Offering costs recorded in accrued liabilities		$ 27