Commitments, Contingencies and Guarantees - Credit Exposure from Loan Commitments (Detail) (USD $) In Millions, unless otherwise specified	May 31, 2013
Commitments And Guarantee Obligations [Line Items]
0 - 12 Months	$ 144.3
1 - 5 Years	596.4
Greater Than 5 Years
Total Corporate Lending Exposure	740.7
Corporate Lending Exposure at Fair Value	182.5
Corporate Lending Commitments	558.2
Non-investment grade [Member]
Commitments And Guarantee Obligations [Line Items]
1 - 5 Years	45.0
Greater Than 5 Years
Total Corporate Lending Exposure	45.0
Corporate Lending Exposure at Fair Value	9.8
Corporate Lending Commitments	35.2
Unrated [Member]
Commitments And Guarantee Obligations [Line Items]
0 - 12 Months	144.3
1 - 5 Years	551.4
Greater Than 5 Years
Total Corporate Lending Exposure	695.7
Corporate Lending Exposure at Fair Value	172.7
Corporate Lending Commitments	$ 523.0