Variable Interest Entities - Assets and Liabilities of Consolidated VIEs Prior to Consolidation (Detail) - USD ($) $ in Millions	Feb. 28, 2017	Nov. 30, 2016
Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	$ 626.8	$ 837.7
Liabilities	626.4	837.2
Securitization Vehicles [Member] | Cash [Member]
Variable Interest Entity [Line Items]
Assets	3.6	16.1
Securitization Vehicles [Member] | Financial Instruments Owned [Member]
Variable Interest Entity [Line Items]
Assets	52.8	86.6
Securitization Vehicles [Member] | Securities Purchased Under Agreement to Resell [Member]
Variable Interest Entity [Line Items]
Assets	570.2	733.5
Securitization Vehicles [Member] | Fees, Interest and Other Receivables [Member]
Variable Interest Entity [Line Items]
Assets	0.2	1.5
Securitization Vehicles [Member] | Other Secured Financings [Member]
Variable Interest Entity [Line Items]
Liabilities	613.5	813.1
Securitization Vehicles [Member] | Other Liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities	12.9	24.1
Other [Member]
Variable Interest Entity [Line Items]
Assets	1.3	1.3
Liabilities	0.2	0.2
Other [Member] | Cash [Member]
Variable Interest Entity [Line Items]
Assets	1.0	0.7
Other [Member] | Financial Instruments Owned [Member]
Variable Interest Entity [Line Items]
Assets	0.3	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	0.0
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	$ 0.2