Revolving Credit Loan Payable (Details) (USD $)	0 Months Ended	1 Months Ended	9 Months Ended	12 Months Ended
	Jul. 12, 2012	Aug. 31, 2014	Apr. 30, 2015	Jul. 31, 2014
Debt Instrument [Line Items]
Maximum principal amount of credit agreement	$ 25,000,000
Line of credit maturity date			Jan. 31, 2017
Line of credit facility, outstanding				13,000,000
Average percentage of commitment fee per annum	0.375%
Maximum amount of investments in and advances to affiliates, at fair value	110,000,000
Repayments of credit agreement		13,000,000
Aggregate loans and advances to affiliates and subsidiaries			74,400,000	73,700,000
Line of credit utilized for letters of credit outstanding amount			0	0
Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, outstanding				$ 13,000,000
Interest rate of credit agreement				1.65%
July 30, 2012 [Member]
Debt Instrument [Line Items]
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.
Prime Rate [Member]
Debt Instrument [Line Items]
U.S Prime Rate basis points	125