Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Income Tax Contingency [Line Items]
Reversal of portion of the valuation allowance			$ 36,900,000
Federal and state net operating loss carryforwards	168,000,000
Foreign net operating losses	200,000,000
Benefit from income taxes	3,982,000	15,872,000	(42,782,000)
Net operating loss carryforwards expiration date	2014
Foreign net operating loss, no expiration	143,000,000
Foreign net operating loss, expiration in two to ten years	57,000,000
Losses limited under Internal Revenue Code	7,000,000
Cumulative undistributed foreign earnings	270,000,000
Accrued interest included in current income taxes payable
Agreement on certain state tax position	356,000		3,754,000
IDT Global [Member]
Income Tax Contingency [Line Items]
Benefit from income taxes	4,100,000
Net2Phone [Member]
Income Tax Contingency [Line Items]
Net operating losses, Federal	$ 84,000,000
Net operating losses expiration description	Through fiscal 2027