Investment Securities (Roll Forward Of OTTI Recognized In Earnings) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance of credit related OTTI, beginning of period	$ 10,460	$ 10,476	$ 10,460	$ 26,320
Reduction for payment of deferred interest	0	(16)	0	(16)
Reduction for securities sold	0	0	0	(15,844)
Balance of credit related OTTI, end of period	$ 10,460	$ 10,460	$ 10,460	$ 10,460