Variable Interest Entities - Non-consolidated VIEs - Additional Information (Detail) - USD ($)	May. 31, 2015	Nov. 30, 2014	Jul. 26, 2010
Variable Interest Entity [Line Items]
Maximum exposure	$ 371,600,000
Agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	3,098,700,000	$ 3,186,900,000
Non agency mortgage-backed securities [Member]
Variable Interest Entity [Line Items]
Carrying amount	983,700,000	1,120,000,000
Jefferies Employee Partners IV, LLC [Member]
Variable Interest Entity [Line Items]
Carrying amount of equity investment	1,100,000	1,200,000
Jefferies Energy Partners I LP [Member]
Variable Interest Entity [Line Items]
Carrying amount	0
Maximum exposure	10,000,000
USA Fund [Member]
Variable Interest Entity [Line Items]
Equity investment in Jefferies SBI USA Fund L.P. (the USA Fund)			$ 75,000,000
Funded equity commitments	60,400,000	60,100,000
Carrying amount of equity investment	$ 23,200,000	$ 43,100,000