Revolving Credit Loan Payable (Details) $ in Thousands		6 Months Ended
	Jul. 12, 2012 USD ($) BasisPoint	Jan. 31, 2016 USD ($)	Jul. 31, 2015 USD ($)
Debt Instrument [Line Items]
Maximum principal amount of credit agreement	$ 25,000
Unused outstanding amount	$ 25,000
Line of credit maturity date		Jan. 31, 2018
Line of credit facility, outstanding
Average percentage of commitment fee per annum	0.375%
Maximum amount of investments in and advances to affiliates, at fair value	$ 110,000
Aggregate loans and advances to affiliates and subsidiaries		$ 83,200	$ 90,100
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		$ 0	$ 0
July 30, 2012 [Member]
Debt Instrument [Line Items]
Interest rate description		The principal outstanding bears 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 | BasisPoint	125