Incapsula - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended		0 Months Ended		3 Months Ended	0 Months Ended		1 Months Ended		3 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Incapsula [Member]	Dec. 31, 2013 Incapsula [Member] Restricted stock units for common stock [Member]	Dec. 31, 2013 Imperva [Member] Restricted stock units for common stock [Member]	Mar. 09, 2010 Series A convertible preferred stock [Member]	Nov. 05, 2009 Series A convertible preferred stock [Member]	Mar. 31, 2014 Series A convertible preferred stock [Member] Times	Mar. 09, 2010 Series A-1 convertible preferred stock [Member]	Mar. 09, 2010 Series A-1 convertible preferred stock [Member] Forward contract [Member]	Jan. 31, 2012 Series A-1 preferred stock [Member]	Jul. 31, 2011 Series A-1 preferred stock [Member]	Mar. 31, 2014 Trailing revenues [Member] Times
Subsidiary or Equity Method Investee [Line Items]
Equity method investments, shares					6,666,666	5,000,000		8,750,000		4,375,000	4,375,000
Ownership interest					76.00%	58.00%				85.00%	82.00%
Value assigned to license						$ 0
Net assets						0
Value of goodwill on the acquisition date	34,972,000					0
Cash consideration					3,000,000			7,000,000
Value assigned to forward contract									0
Cash consideration										3,500,000	3,500,000
Enterprise valuation for computation of share price							7					8
Value assigned to Purchase Right							0
Amount paid for remaining outstanding capital stock		7,700,000
Business acquisition, shares issued		48,359		264,878
Common stock exchange to acquire outstanding capital stock		124,088
Common stock subject to holdback		34,485
Common stock subject to holdback, period		15 months
Shares issuable, as-converted to common stock-basis			198,825
Non-controlling interest reclassified to additional paid-in capital	$ 2,800,000