Variable Interest Entities - Assets and Liabilities of Consolidated VIEs Prior to Consolidation (Detail) (USD $) In Millions, unless otherwise specified	Feb. 28, 2015	Nov. 30, 2014
Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	$ 861.4	$ 638.3
Liabilities	861.4	638.3
Other [Member]
Variable Interest Entity [Line Items]
Assets	0.5	0.5
Liabilities	0.2	0.2
Cash [Member] | Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	0	0
Cash [Member] | Other [Member]
Variable Interest Entity [Line Items]
Assets	0.2	0.2
Financial Instruments Owned [Member] | Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	65.6	62.7
Financial Instruments Owned [Member] | Other [Member]
Variable Interest Entity [Line Items]
Assets	0.3	0.3
Securities Purchased Under Agreement to Resell [Member] | Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	795.4	575.2
Securities Purchased Under Agreement to Resell [Member] | Other [Member]
Variable Interest Entity [Line Items]
Assets	0	0
Fees, Interest and Other Receivables [Member] | Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	0.4	0.4
Fees, Interest and Other Receivables [Member] | Other [Member]
Variable Interest Entity [Line Items]
Assets	0	0
Other Secured Financings [Member] | Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Liabilities	860.6	637.7
Other Secured Financings [Member] | Other [Member]
Variable Interest Entity [Line Items]
Liabilities	0	0
Other Liabilities [Member] | Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Liabilities	0.8	0.6
Other Liabilities [Member] | Other [Member]
Variable Interest Entity [Line Items]
Liabilities	$ 0.2	$ 0.2