Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Footnote) (Detail) (USD $) In Millions, unless otherwise specified	Feb. 28, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Exchange traded derivative assets	$ 67.9
Cash collateral received	377.0
Exchange traded derivative liabilities, with fair value	28.0
Cash collateral pledged	$ 458.4