Variable Interest Entities - Non-consolidated VIEs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	May 31, 2014	May 31, 2013	Feb. 28, 2013	May 31, 2014 Jefferies Employee Partners IV, LLC [Member]	Nov. 30, 2013 Jefferies Employee Partners IV, LLC [Member]	May 31, 2014 USA Fund [Member]	Nov. 30, 2013 USA Fund [Member]
Variable Interest Entity [Line Items]
Additional financial support to securitization of vehicles	$ 0	$ 0	$ 0
Equity investment in Jefferies SBI USA Fund L.P. (the "USA Fund")						75.0
Funded equity commitments						58.8	47.0
Carrying amount of equity investment				$ 1.3	$ 1.6	$ 43.9	$ 39.2