Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-controlling Interest [Member]
Beginning balance at Dec. 31, 2012	$ 84,231	$ 2	$ 157,989	$ (73,517)	$ 861	$ (1,104)
Beginning balance, shares at Dec. 31, 2012		24,296,076
Issuance of common stock, net of repurchases	4,796		4,796
Issuance of common stock, net of repurchases, shares		806,226
Vesting of restricted stock	801		801
Stock-based compensation	22,494		22,494
Issuance of common stock in connection with employee stock purchase plan	2,772		2,772
Issuance of common stock in connection with employee stock purchase plan, shares		96,502
Exercise of warrant, shares		7,694
Shares withheld for tax withholding on vesting of restricted stock units	(1,252)		(1,252)
Sale of additional ownership interest in Incapsula, Inc.			357			(357)
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(172)				(172)
Change in unrealized loss on derivatives	(1,117)				(1,117)
Net loss	(26,331)			(25,178)		(1,153)
Comprehensive loss	(27,620)
Ending balance at Dec. 31, 2013	86,222	$ 2	187,957	(98,695)	(428)	(2,614)
Ending balance, shares at Dec. 31, 2013		25,206,498
Issuance of common stock related to acquisitions	24,163		24,163
Issuance of common stock related to acquisitions, shares		738,479
Issuance of common stock, net of repurchases	7,371		7,371
Issuance of common stock, net of repurchases, shares		672,832
Vesting of restricted stock	454		454
Stock-based compensation	37,273		37,273
Issuance of common stock in connection with employee stock purchase plan	3,332		3,332
Issuance of common stock in connection with employee stock purchase plan, shares		188,068
Income tax benefit from employee stock option exercises	385		385
Shares withheld for tax withholding on vesting of restricted stock units	(2,074)		(2,074)
Pre-combination service relating to acquired Skyfence option plan	354		354
Purchase of additional ownership interest in Incapsula, Inc.			(2,827)			2,827
Purchase of additional ownership interest in Incapsula, Inc. Shares		89,603
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(59)				(59)
Change in unrealized loss on derivatives	(1,002)				(1,002)
Net loss	(59,176)			(58,963)		$ (213)
Comprehensive loss	(60,237)
Ending balance at Dec. 31, 2014	97,243	$ 2	256,388	(157,658)	(1,489)
Ending balance, shares at Dec. 31, 2014		26,895,480
Proceeds from follow-on public offering, net of offering costs	127,741	$ 1	127,740
Proceeds from follow-on public offering, net of offering costs, shares		3,450,000
Issuance of common stock, net of repurchases	18,724		18,724
Issuance of common stock, net of repurchases, shares		670,844
Vesting of restricted stock	767		767
Vesting of restricted stock, shares		706,121
Stock-based compensation	50,964		50,964
Issuance of common stock in connection with employee stock purchase plan	4,785		4,785
Issuance of common stock in connection with employee stock purchase plan, shares		114,699
Income tax benefit from employee stock option exercises	165		165
Shares withheld for tax withholding on vesting of restricted stock units	(11,464)		(11,464)
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(249)				(249)
Change in unrealized loss on derivatives	407				407
Net loss	(48,882)			(48,882)
Comprehensive loss	(48,724)
Ending balance at Dec. 31, 2015	$ 240,201	$ 3	$ 448,069	$ (206,540)	$ (1,331)
Ending balance, shares at Dec. 31, 2015		31,837,144