Securities (Summary Of Cumulative Credit-Related OTTI Charges) (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Beginning balance	$ 18,398	$ 18,332
Loss where impairment was not previously recognized	119
Additional loss where impairment was previously recognized		37
Reduction due to credit impaired securities sold	(1,243)
Ending balance	17,274	18,369
Collateralized Debt Obligations [Member]
Beginning balance	18,369	18,332
Loss where impairment was not previously recognized	119
Additional loss where impairment was previously recognized		37
Reduction due to credit impaired securities sold	(1,214)
Ending balance	17,274	18,369
Residential Non-Agency Collateralized Mortgage Obligations [Member]
Beginning balance	29
Reduction due to credit impaired securities sold	$ (29)