Commitments, Contingencies and Guarantees - Credit Exposure from Loan Commitments (Detail) (USD $) In Millions, unless otherwise specified	May 31, 2014
Commitments And Guarantee Obligations [Line Items]
2014	$ 14.8
2015-2019	789.3
2020 and Later
Total Corporate Lending Exposure	804.1
Corporate Lending Exposure at Fair Value	76.0
Corporate Lending Commitments	728.1
Investment grade [Member]
Commitments And Guarantee Obligations [Line Items]
2014
2015-2019	69.4
2020 and Later
Total Corporate Lending Exposure	69.4
Corporate Lending Exposure at Fair Value
Corporate Lending Commitments	69.4
Non-investment grade [Member]
Commitments And Guarantee Obligations [Line Items]
2014
2015-2019	78.9
2020 and Later
Total Corporate Lending Exposure	78.9
Corporate Lending Exposure at Fair Value	17.9
Corporate Lending Commitments	61.0
Unrated [Member]
Commitments And Guarantee Obligations [Line Items]
2014	14.8
2015-2019	641.0
2020 and Later
Total Corporate Lending Exposure	655.8
Corporate Lending Exposure at Fair Value	58.1
Corporate Lending Commitments	$ 597.7