Securities Sold Under Agreements To Repurchase And Other Short-Term Borrowings (Summary Of Securities Sold Under Agreements To Repurchase And Other Short-Term Borrowings) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Securities Sold Under Agreements to Repurchase and Other Short-term Borrowings [Line Items]
Callable at the option of the counterparty	$ 1,054,815	$ 941,706
Federal funds purchased	255,200	223,000
Total	1,310,015	1,164,706
Original Maturity Of One Year Or Less [Member]
Securities Sold Under Agreements to Repurchase and Other Short-term Borrowings [Line Items]
Callable at the option of the counterparty	304,815	290,856
Callable At The Option Of The Counterparty [Member]
Securities Sold Under Agreements to Repurchase and Other Short-term Borrowings [Line Items]
Callable at the option of the counterparty	300,000	400,000
Non-Callable [Member]
Securities Sold Under Agreements to Repurchase and Other Short-term Borrowings [Line Items]
Callable at the option of the counterparty	$ 450,000	$ 250,850