Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating results for the business segments
Total revenues	$ 48,810	$ 55,134	$ 179,158	$ 140,465
Income (Loss) from operations	(4,344)	(5,569)	(10,837)	(2,937)
Research and development	2,369	2,592	4,469	5,081
Equity in the net loss of AMSO, LLC		806		1,935
IDT Energy [Member]
Operating results for the business segments
Total revenues	48,810	55,134	179,158	140,465
Income (Loss) from operations	940	520	31	9,375
Research and development
Equity in the net loss of AMSO, LLC
Genie Oil and Gas [Member]
Operating results for the business segments
Total revenues
Income (Loss) from operations	(2,769)	(3,888)	(5,206)	(7,808)
Research and development	2,369	2,592	4,469	5,081
Equity in the net loss of AMSO, LLC		806		1,935
Corporate [Member]
Operating results for the business segments
Total revenues
Income (Loss) from operations	(2,515)	(2,201)	(5,662)	(4,504)
Research and development
Equity in the net loss of AMSO, LLC

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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