Commitments, Contingencies and Guarantees - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	1 Months Ended
	Oct. 31, 2014	Jan. 31, 2013	Feb. 28, 2015
Commitments Contingencies And Guarantees [Line Items]
Loan commitments outstanding to clients			$ 353.5
Fair value of mortgage-related commitments			154.9
Litigation settlement amount	70.0	25.0
Litigation reserve			1.0
Fair value of derivative contracts approximated deemed to meet the definition of a guarantee			567.1
Maximum amount payable under guarantee			31.0
Standby Letters of Credit [Member]
Commitments Contingencies And Guarantees [Line Items]
Letters of credit commitments			45.9
Litigation Client [Member]
Commitments Contingencies And Guarantees [Line Items]
Litigation settlement amount		11.0
U.S. Attorney Office [Member]
Commitments Contingencies And Guarantees [Line Items]
Litigation settlement amount		10.0
Securities and Exchange Commission [Member]
Commitments Contingencies And Guarantees [Line Items]
Litigation settlement amount		4.0
Jefferies Capital Partners LLC [Member]
Commitments Contingencies And Guarantees [Line Items]
Outstanding Equity Commitments			30.0
Other Investments [Member]
Commitments Contingencies And Guarantees [Line Items]
Outstanding Equity Commitments			$ 4.5