Investment Securities (Schedule Of Trust Preferred Securities - Pooled Issuers For OTTI Information) (Detail) (USD $) In Thousands, unless otherwise specified					9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Pooled Trust Preferred Securities [Member]	Dec. 31, 2011 Pooled Trust Preferred Securities [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] Preferred Class B [Member] Security H [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] Preferred Class B [Member] Security I [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] Preferred Class B [Member] Security J [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] Preferred Class B [Member] Security L [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] Preferred Class A [Member] Security K [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] Preferred Class A [Member] Security M [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] Preferred Class A [Member] Security N [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost	$ 3,051,434	$ 2,849,463	$ 49,583	$ 52,606	$ 3,486	$ 4,467	$ 5,297	$ 8,725	$ 7,391	$ 7,227	$ 12,990
Gross Unrealized Losses	(35,881)	(51,186)	(21,330)	(23,608)	(1,704)	(2,181)	(2,786)	(4,370)	(3,532)	(4,331)	(2,426)
Fair Value			28,253		1,782	2,286	2,511	4,355	3,859	2,896	10,564
Lowest Credit Ratings					B	CCC	CCC	CCC	CCC	D	A
Total Other-Than-Temporary Impairment			$ (10,460)		$ (352)	$ (365)	$ (806)	$ (867)	$ (2,040)	$ (4,926)	$ (1,104)
% of Performing Bank/Insurance Issuers					92.00%	87.50%	88.90%	91.70%	68.60%	53.90%	88.90%
Current Deferrals/Defaults (As a % of Original Collateral)					7.20%	17.20%	13.90%	12.30%	34.30%	40.10%	13.90%