Business Segment Information (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary total assets for the business segments
Total assets	$ 158,843	$ 150,306	$ 150,194
IDT Energy [Member]
Summary total assets for the business segments
Total assets	76,691	65,377	60,483
Genie Oil and Gas [Member]
Summary total assets for the business segments
Total assets	42,193	36,561	2,498
Corporate [Member]
Summary total assets for the business segments
Total assets	$ 39,959	$ 48,368	$ 87,213