Capital Stock - Option and Performance-Based Restricted Share Unit Activity Under Incapsula Plan (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	2,279,081	1,044,651
Number of Restricted Stock Units Outstanding, Granted	911,734	1,368,761
Number of Restricted Stock Units Outstanding, Exercised/Released	898,205	238,446
Number of Restricted Stock Units Outstanding, Forfeited	(643,805)	(225,853)
Number of Restricted Stock Units Outstanding, Unvested - Ending balance	1,898,025	2,279,081	1,044,651
Number of Stock Options Outstanding, Outstanding - Beginning balance	2,244,363	1,675,506	1,989,237
Number of Stock Options Outstanding, Granted	696,971	1,256,559	631,775
Number of Stock Options Outstanding, Exercised/Released	(636,424)	(496,297)	(687,719)
Number of Stock Options Outstanding, Forfeited	(355,821)	(264,012)	(257,787)
Number of Stock Options Outstanding, Outstanding - Ending balance	1,949,089	2,244,363	1,675,506
Weighted Average Exercise Price of Stock Options Outstanding	$ 39.27	$ 33.83	$ 23.78	$ 14.08
Weighted Average Exercise Price of Stock Options Outstanding, Granted	49.20	41.39	36.55
Weighted Average Exercise Price of Stock Options Outstanding, Exercised/Released	29.44	14.85	6.94
Weighted Average Exercise Price of Stock Options Outstanding, Forfeited	$ 42.00	$ 35.85	$ 25.11
Incapsula Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Outstanding - Beginning Balance	0	89,687	2,753,708
Additional shares authorized			5,529,878
Shares Available for Grant, Granted		(95,000)
Shares Available for Grant, Exercised/Released			0
Shares Available for Grant, Forfeited		15,213	141,562
Shares Available for Grant, Transferred to Imperva 2011 stock option plan		(9,900)
Shares Available for Grant, Outstanding - Ending Balance		0	89,687
Number of Stock Options Outstanding, Outstanding - Beginning balance	0	1,806,500	1,836,500
Number of Stock Options Outstanding, Granted		95,000
Number of Stock Options Outstanding, Exercised/Released			(1,128,438)
Number of Stock Options Outstanding, Forfeited		(2,500)	(141,562)
Number of Stock Options Outstanding, Transferred to Imperva 2011 stock option plan		(1,899,000)
Number of Stock Options Outstanding, Outstanding - Ending balance		0	1,806,500
Weighted Average Exercise Price of Stock Options Outstanding		$ 0	$ 0.47	$ 0.10
Weighted Average Exercise Price of Stock Options Outstanding, Granted		1.25
Weighted Average Exercise Price of Stock Options Outstanding, Exercised/Released			0.02
Weighted Average Exercise Price of Stock Options Outstanding, Forfeited		1.25	0.22
Weighted Average Exercise Price of Stock Options Outstanding, Transferred to Imperva 2011 stock option plan		$ 0.16	$ 0
Incapsula Plan [Member] | Performance RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Granted			(7,095,461)
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	0	7,095,461	0
Number of Restricted Stock Units Outstanding, Additional Stock authorized			0
Number of Restricted Stock Units Outstanding, Granted		0	7,095,461
Number of Restricted Stock Units Outstanding, Exercised/Released			0
Number of Restricted Stock Units Outstanding, Forfeited		(12,713)	0
Number of Restricted Stock Units Outstanding, Transferred to Imperva 2011 stock option plan		(7,082,748)
Number of Restricted Stock Units Outstanding, Unvested - Ending balance		0	7,095,461
Number of Stock Options Outstanding, Granted			0
Weighted Average Exercise Price of Stock Options Outstanding, Granted			$ 0
Incapsula Plan [Member] | Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Granted			(1,240,000)
Number of Restricted Stock Units Outstanding, Granted			0
Number of Stock Options Outstanding, Granted			1,240,000
Weighted Average Exercise Price of Stock Options Outstanding, Granted			$ 0.58