Revolving Credit Loan Payable - Additional Information (Detail) (USD $)	0 Months Ended		1 Months Ended		9 Months Ended		12 Months Ended			3 Months Ended	9 Months Ended
	Aug. 30, 2013	Jul. 12, 2012	Feb. 28, 2014	Nov. 30, 2013	Apr. 30, 2014	Apr. 30, 2013	Jul. 31, 2013	Apr. 30, 2014 Line of Credit [Member]	Jul. 31, 2013 Line of Credit [Member]	May 28, 2014 Subsequent Event [Member]	Apr. 30, 2014 July 30, 2012 [Member]	Jul. 12, 2013 Prime Rate [Member] BasisPoint
Debt Instrument [Line Items]
Maximum principal amount of credit agreement		$ 25,000,000
Interest rate description											Interest per annum, at the option of IDT Telecom, at either (a) the U.S. Prime Rate less 125 basis points, or (b) the LIBOR rate adjusted by the Regulation D maximum reserve requirement plus 150 basis points.
U.S Prime Rate basis points												125
Line of credit facility, outstanding					13,000,000		21,062,000	15,000,000	21,100,000
Interest rate of credit agreement					1.65%		1.69%
Average percentage of commitment fee per annum		0.375%
Maximum amount of investments in and advances to affiliates, at fair value		90,000,000
Proceeds from credit agreement					43,000,000
Repayments of credit agreement	21,100,000		15,000,000	15,000,000						13,000,000
Aggregate loans and advances to affiliates and subsidiaries					29,700,000
Line of credit utilized for letters of credit outstanding amount					$ 0		$ 0