Commitments, Contingencies and Guarantees - Credit Exposure from Loan Commitments (Detail) $ in Millions	May. 31, 2015 USD ($)
Commitments And Guarantee Obligations [Line Items]
2015	$ 115.0
2016-2020	1,036.5
2021 and Later	0.0
Total Corporate Lending Exposure	1,151.5
Corporate Lending Exposure at Fair Value	194.0
Corporate Lending Commitments	957.5
Non-investment grade [Member]
Commitments And Guarantee Obligations [Line Items]
2015	0.0
2016-2020	171.9
2021 and Later	0.0
Total Corporate Lending Exposure	171.9
Corporate Lending Exposure at Fair Value	9.7
Corporate Lending Commitments	162.2
Unrated [Member]
Commitments And Guarantee Obligations [Line Items]
2015	115.0
2016-2020	864.6
2021 and Later	0.0
Total Corporate Lending Exposure	979.6
Corporate Lending Exposure at Fair Value	184.3
Corporate Lending Commitments	$ 795.3