Other Operating (Losses) Gains, Net - Summary of Other Operating (Losses) Gains, Net by Business Segment (Detail) (USD $)	0 Months Ended		1 Months Ended				3 Months Ended						12 Months Ended
	Jan. 17, 2012	Mar. 22, 2010	Oct. 13, 2011	Aug. 31, 2011	Dec. 31, 2010	Mar. 31, 2010	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Jan. 31, 2011	Oct. 31, 2010	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009	Jul. 31, 2008	Jul. 31, 2007	Feb. 15, 2011
Other Operating Loss Income Net [Line Items]
Telecom Platform Services-estimated losses from pending litigation													$ (6,468,000)
Telecom Platform Services-(loss) gain on settlement of litigation													(11,252,000)		10,000,000
Telecom Platform Services-gain on settlement of claims													1,750,000		418,000
Telecom Platform Services-gain on termination of agreement											14,400,000			14,375,000
Telecom Platform Services-loss from alleged patent infringement										(1,100,000)	(9,800,000)			(10,828,000)
Corporate-other													100,000	(500,000)
All Other-gain on sale of wireless spectrum													5,330,000
All Other-gain on insurance claim														2,637,000
All Other-gain on settlement of IDT Global Israel claims															485,000
All Other-gain on sale of land and building															681,000
All Other-gain (loss) on settlement of other claims												600,000		640,000	(1,500,000)
TOTAL							(1,100,000)	1,800,000	(11,300,000)		4,900,000	2,500,000	(10,540,000)	6,324,000	10,084,000
Telecom Platform Services-estimated losses from pending litigation													6,500,000
Payment for settlement of disputes			10,000,000
Legal fees incurred													1,000,000
Loss on settlement of unrelated claim													200,000
Litigation settlement date																		March 22, 2010
Cash received from defendants		10,000,000
Payment received on bankruptcy settlement	1,800,000
Payment received for termination of agreement					14,400,000
Damages awarded by court																			9,100,000
Damages awarded for alleging infringement of patents				10,100,000
Legal fees incurred for law suit				700,000
Cash in exchange of licenses													6,800,000
Gain on sale of licenses													5,300,000
Proceeds on insurance related to water damages														3,500,000	500,000
Estimated carrying value of damaged building and improvements										1,100,000				1,100,000
Gain on insurance claim														2,600,000
Disposition of issued and outstanding shares																100.00%	100.00%
Gain on dispostion						500,000
Cash on sale of land and building															3,100,000
All Other-gain on sale of land and building(i)															$ 700,000