Repurchase Arrangements And Similar Borrowings, Including Related Hedging Activity (Schedule Of Average Borrowing Outstanding) (Detail) (Average Borrowings And Rates For The Indicated Quarters, Adjusted For The Effects Of Related Derivatives Held As Cash Flow Hedges [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Average Borrowings And Rates For The Indicated Quarters, Adjusted For The Effects Of Related Derivatives Held As Cash Flow Hedges [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Average Borrowings	$ 12,833,675	$ 11,278,675
Average Rate	0.56%	0.54%