Commitments, Contingencies and Guarantees - Additional Information (Detail) $ in Millions	6 Months Ended
	May 31, 2018 USD ($)
Loss Contingencies [Line Items]
Loan commitments outstanding to clients	$ 86.1
Fair value of mortgage-related commitments	0.9
Fair value of derivative contracts approximated deemed to meet the definition of a guarantee	299.5
Standby Letters of Credit
Loss Contingencies [Line Items]
Letters of credit commitments	51.8
Jefferies Capital Partners LLC
Loss Contingencies [Line Items]
Outstanding equity commitments	18.4
Other Investments
Loss Contingencies [Line Items]
Outstanding equity commitments	$ 3.6
Maximum | Standby Letters of Credit
Loss Contingencies [Line Items]
Standby letters of credit expiration period	1 year