Investment Securities (Roll Forward Of Credit Losses Of Held-To-Maturity Securities Written Down As Other-Than-Temporary Impairment Recognized In Earnings And Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Investment Securities [Abstract]
Balance, beginning of period	$ 9,574	$ 12,778
Subsequent OTTI credit losses		25
Balance, end of period	$ 9,574	$ 12,803