Assets Measured at Fair Value on Nonrecurring Basis (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for Credit Losses	$ 5.0	$ 10.0	$ 10.0	$ 25.0
Other Operating Expenses	62.9	56.7	136.0	130.9
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	4.7	5.2	14.2	4.7
Other Operating Expenses	$ 0.3	$ 0.8	$ 0.6	$ 0.9