Investment Securities (Rollforward Of Total Amount Of Credit-Related OTTI) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investment [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	$ 0	$ 0	$ 104,551
HTM Securities Transfered to AFS Securities	0	0
Reductions for securities sold during the period	0	104,551
Held-to-maturity Securities [Member]
Investment [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	0	0	9,079
HTM Securities Transfered to AFS Securities	0	9,079
Reductions for securities sold during the period	0	0
Available-for-sale Securities [Member]
Investment [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	0	0	$ 95,472
HTM Securities Transfered to AFS Securities	0	(9,079)
Reductions for securities sold during the period	$ 0	$ 104,551