Short-Term Borrowings (Additional Information On Short-Term Borrowings) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Short-Term Borrowings [Abstract]
Outstanding at December 31st	$ 395,543	$ 220,328	$ 263,351
Maximum month-end outstanding balance	395,543	289,248	263,351
Average daily outstanding balance	$ 220,146	$ 216,116	$ 197,824
Average rate during the year	0.26%	0.38%	0.66%
Average rate at year end	0.27%	0.24%	0.48%