Securities (Summary Of Cumulative Credit-Related OTTI Charges) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance	$ 17,367	$ 18,398
Loss where impairment was not previously recognized
Additional loss where impairment was previously recognized
Reduction due to credit impaired securities sold	(212)
Ending balance	17,155	18,398
Collateralized Debt Obligations [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance	17,155	18,369
Loss where impairment was not previously recognized
Additional loss where impairment was previously recognized
Ending balance	17,155	18,369
Residential Non-Agency Collateralized Mortgage Obligations [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance	212	29
Loss where impairment was not previously recognized
Additional loss where impairment was previously recognized
Reduction due to credit impaired securities sold	(212)
Ending balance		$ 29