Average Recorded Investment in Impaired Loans and Interest Income that would have been Recorded on Nonperforming Loans (Detail) (USD $) In Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Financing Receivable, Impaired [Line Items]
Average Recorded Investment in Impaired Loans	$ 269.4	[1]	$ 230.5	[1]	$ 277.2	[1]	$ 221.5	[1]
Interest Income that would have been Recorded on Nonperforming Loans in Accordance with their Original Terms	$ 3.9		$ 3.5		$ 8.1		$ 7.6

[1] Average recorded investment in impaired loans is calculated as the average of the month-end impaired loan balances for the period.