Commitments, Contingencies and Guarantees - Commitments and Contingencies (Detail) $ in Millions	May. 31, 2015 USD ($)
Commitments And Guarantee Obligations [Line Items]
2015	$ 3,395.5
2016	1,815.5
2017 and 2018	887.4
2019 and 2020	66.1
2021 and Later	295.2
Notional/ Maximum Payout	6,459.7
Equity commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	0.0
2016	9.2
2017 and 2018	0.9
2019 and 2020	0.0
2021 and Later	257.7
Notional/ Maximum Payout	267.8
Loan commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	34.3
2016	475.7
2017 and 2018	387.4
2019 and 2020	60.1
2021 and Later	0.0
Notional/ Maximum Payout	957.5
Mortgage-related and other purchase commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	909.9
2016	1,330.6
2017 and 2018	499.1
2019 and 2020	0.0
2021 and Later	0.0
Notional/ Maximum Payout	2,739.6
Underwriting commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	36.9
2016	0.0
2017 and 2018	0.0
2019 and 2020	0.0
2021 and Later	0.0
Notional/ Maximum Payout	36.9
Forward starting reverse repos and repos [Member]
Commitments And Guarantee Obligations [Line Items]
2015	2,384.4
2016	0.0
2017 and 2018	0.0
2019 and 2020	0.0
2021 and Later	0.0
Notional/ Maximum Payout	2,384.4
Other unfunded commitments [Member]
Commitments And Guarantee Obligations [Line Items]
2015	30.0
2016	0.0
2017 and 2018	0.0
2019 and 2020	6.0
2021 and Later	37.5
Notional/ Maximum Payout	$ 73.5