Variable Interest Entities - Assets and Liabilities of Consolidated VIEs Prior to Consolidation (Detail) - USD ($) $ in Millions	May 31, 2017	Nov. 30, 2016
Securitization Vehicles [Member]
Variable Interest Entity [Line Items]
Assets	$ 412.1	$ 837.7
Liabilities	411.3	837.2
Securitization Vehicles [Member] | Cash [Member]
Variable Interest Entity [Line Items]
Assets	5.3	16.1
Securitization Vehicles [Member] | Financial Instruments Owned [Member]
Variable Interest Entity [Line Items]
Assets	36.3	86.6
Securitization Vehicles [Member] | Securities Purchased Under Agreement to Resell [Member]
Variable Interest Entity [Line Items]
Assets	370.3	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	404.1	813.1
Securitization Vehicles [Member] | Other Liabilities [Member]
Variable Interest Entity [Line Items]
Liabilities	7.2	24.1
Other [Member]
Variable Interest Entity [Line Items]
Assets	1.4	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	0.4	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