Commitments, Contingencies and Guarantees - Additional Information (Detail) $ in Millions	9 Months Ended
	Aug. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Loan commitments outstanding to clients	$ 64.9
Fair value of mortgage-related commitments	44.5
Fair value of derivative contracts approximated deemed to meet the definition of a guarantee	245.5
Maximum amount payable under guarantee	0.2
Standby Letters of Credit
Loss Contingencies [Line Items]
Letters of credit commitments	54.0
Jefferies Capital Partners LLC
Loss Contingencies [Line Items]
Outstanding equity commitments	22.0
Other Investments
Loss Contingencies [Line Items]
Outstanding equity commitments	$ 1.5
Maximum | Standby Letters of Credit
Loss Contingencies [Line Items]
Standby letters of credit expiration period	1 year