Variable Interest Entities - Assets and Liabilities of Consolidated VIEs Prior to Consolidation (Detail) - USD ($) $ in Millions	Aug. 31, 2016	Nov. 30, 2015
Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	$ 704.8	$ 786.4
Liabilities	704.1	786.4
Securitization Vehicles [Member] | Cash [Member]
Variable Interest Entity [Line Items]
Assets	9.7	0.5
Securitization Vehicles [Member] | Financial Instruments Owned [Member]
Variable Interest Entity [Line Items]
Assets	90.6	68.3
Securitization Vehicles [Member] | Securities Purchased Under Agreement to Resell [Member]
Variable Interest Entity [Line Items]
Assets	604.0	717.3
Securitization Vehicles [Member] | Fees, Interest and Other Receivables [Member]
Variable Interest Entity [Line Items]
Assets	0.5	0.3
Securitization Vehicles [Member] | Other Secured Financings [Member]
Variable Interest Entity [Line Items]
Liabilities	692.8	785.0
Securitization Vehicles [Member] | Other Liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities	11.3	1.4
Other [Member]
Variable Interest Entity [Line Items]
Assets	1.3	2.3
Liabilities	0.2	0.3
Other [Member] | Cash [Member]
Variable Interest Entity [Line Items]
Assets	0.7	1.5
Other [Member] | Financial Instruments Owned [Member]
Variable Interest Entity [Line Items]
Assets	0.6	0.6
Other [Member] | Securities Purchased Under Agreement to Resell [Member]
Variable Interest Entity [Line Items]
Assets	0.0	0.0
Other [Member] | Fees, Interest and Other Receivables [Member]
Variable Interest Entity [Line Items]
Assets	0.0	0.2
Other [Member] | Other Secured Financings [Member]
Variable Interest Entity [Line Items]
Liabilities	0.0	0.0
Other [Member] | Other Liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities	$ 0.2	$ 0.3