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Purchase shares of capital stock.

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Description of the conversion terms of a debt instrument which may include the conversion ratio (including all potential conversion ratios if contingently adjustable), type of debt or equity security into which the debt is convertible, the dollars of debt or the number of shares into which the instrument is convertible (or potentially convertible into), the conversion period, any contingencies associated with the conversion terms, and the existence and amount of a beneficial conversion feature.

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Face (par) amount of debt instrument at time of issuance.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Details Textual) - USD ($) $ in Thousands	6 Months Ended
	Jan. 31, 2018	Sep. 19, 2017	Sep. 14, 2017	Jul. 31, 2017
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Marketable securities	$ 46,202			$ 58,272
Series C convertible notes	24,350			$ 26,894
Howard S. Jonas [Member] \| IDT Corporation [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Percentage of contractual right to receive additional shares		9.00%
Rafael Holdings, Inc. [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Spin off cash and marketable securities to be distributed	44,000
Investments	6,000
Rafael Pharmaceuticals, Inc. [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Maximum exposure to loss	11,700
Rafael Pharmaceuticals, Inc. [Member] \| Convertible promissory note [Member] \| Howard and Deborah Jonas [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Series C convertible notes	525
Rafael Pharmaceuticals, Inc. [Member] \| Convertible promissory note [Member] \| The Howard S. and Deborah Jonas Foundation [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Series C convertible notes	$ 525
CS Pharma Holdings, LLC [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Holds percentages of interest	50.00%
CS Pharma Holdings, LLC [Member] \| Convertible promissory note ("Series D Note") [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Purchase shares of capital stock percentage	56.00%
Exercise warrants value	$ 10,000
Warrant, description	The exercise price of the warrant is the lower of 70% of the price sold in an equity financing, or $1.25 per share, subject to certain adjustments. The minimum initial and subsequent exercises of the warrant shall be for such number of shares that will result in at least $5 million of gross proceeds to Rafael Pharma, or such lesser amount as represents 5% of the outstanding capital stock of Rafael Pharma, or such lesser amount as may then remain unexercised. The warrant will expire upon the earlier of December 31, 2020 or a qualified initial public offering or liquidation event.
Warrants expiry date	Dec. 31, 2020
Convertible promissory note, principal amount	$ 10,000
Convertible promissory note, rate of interest	3.50%
Convertible promissory note, maturity date	Sep. 16, 2018
Initial amount of investment amounts paid	$ 5,000
Convertible notes conversion features, description	The Series D Note also includes a mandatory conversion into Rafael Pharma common stock upon a qualified initial public offering, and conversion at the holder's option upon an unqualified financing event. In all cases, the Series D Note conversion price is based on the applicable financing purchase price.
IDT-Rafael Holdings, LLC [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Contractual right to receive additional shares, description	(i) Food and Drug Administration approval of a Rafael Pharma drug application, (ii) an initial public offering of Rafael Pharma at a valuation of over $500 million, or (iii) a sale of Rafael Pharma above certain valuations. Currently, none of the conditions have been satisfied and the right remains contingent. On September 14, 2017, IDT-Rafael Holdings distributed this right to its members on a pro rata basis such that the Company received the right to 9% of the outstanding capital stock of Rafael Pharma and Howard S. Jonas, the Company's Chairman of the Board, and Chairman of the Board of Rafael Pharma, received the right to 1% of the outstanding capital stock of Rafael Pharma. In addition, as compensation for assuming the role of Chairman of the Board of Rafael Pharma, and to create additional incentive to contribute to the success of Rafael Pharma, on September 19, 2017, the Company transferred its right to receive 9% of the outstanding capital stock of Rafael Pharma to Mr. Jonas. The right is further transferable at the discretion of Mr. Jonas.
Percentage of contractual right to receive additional shares	10.00%
IDT-Rafael Holdings, LLC [Member] \| IDT Corporation [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Percentage of contractual right to receive additional shares			9.00%
IDT-Rafael Holdings, LLC [Member] \| Howard S. Jonas [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Percentage of contractual right to receive additional shares			1.00%
Holds percentages of interest	10.00%
IDT-Rafael Holdings, LLC [Member] \| Rafael Holdings, Inc. [Member]
Proposed Spin-Off of Rafael Holdings, Inc. and Investment in Rafael Pharmaceuticals, Inc. (Textual)
Holds percentages of interest	90.00%