Assets Measured at Fair Value on Nonrecurring Basis (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for Credit Losses	$ 10.0	$ 17.5	$ 20.0	$ 42.5
Other Operating Expenses	63.0	62.0	199.0	192.9
Fair Value, Inputs, Level 3 | Loans | Specific Allowances
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for Credit Losses	5.7	3.0	(8.5)	10.5
Other Operating Expenses	$ 0.2	$ 1.7	$ 0.4	$ 1.8