Assets Measured at Fair Value on Nonrecurring Basis (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for Credit Losses	$ 5.0	$ 15.0
Other Operating Expenses	73.1	74.2
Loans | Fair Value, Inputs, Level 3 | Specific Allowances
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for Credit Losses	(9.5)	3.1
Other Operating Expenses	$ 0.1	$ 0.3