Borrowed Funds (Summary Of Comparative Data For Securities Sold Under Agreements To Repurchase) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Federal Funds Purchased [Member]
Borrowed Funds [Line Items]
Average amount outstanding during the year	$ 27	[1]			$ 8,392	[1]
Maximum amount outstanding at month-end					85,000	[2]
Balance, December 31
Weighted-average interest rate for the year	1.29%		0.00%		0.27%
Securities Sold Under Agreements To Repurchase [Member]
Borrowed Funds [Line Items]
Average amount outstanding during the year	1,448,363	[1]	1,560,215	[1]	1,562,447	[1]
Maximum amount outstanding at month-end	1,559,000	[3]	1,566,000	[3]	1,587,000	[3]
Balance, December 31	$ 1,400,000		$ 1,561,000		$ 1,557,000
Rate at year-end	4.14%		4.18%		4.19%
Weighted-average interest rate for the year	4.19%		4.24%		4.17%

[1] Average balances were computed using daily averages.

[2] Highest month-end balances were April 2009.

[3] Highest month-end balances were January 2011, September 2010, and February 2009.