Bank's Investment in Trust Preferred Securities (Detail) (USD $) In Thousands, unless otherwise specified			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Pooled Trust Preferred Securities	Mar. 31, 2013 Pooled Trust Preferred Securities Alesco Preferred Funding IX Entity		Mar. 31, 2013 Pooled Trust Preferred Securities Preferred Term Securities XIII Entity		Mar. 31, 2013 Pooled Trust Preferred Securities Preferred Term Securities XVIII Entity		Mar. 31, 2013 Pooled Trust Preferred Securities Preferred Term Securities XXVII Entity		Mar. 31, 2013 Pooled Trust Preferred Securities U.S. Capital Funding I Entity		Mar. 31, 2013 Pooled Trust Preferred Securities U.S. Capital Funding III Entity
Investment Holdings [Line Items]
Class				A2A		B1		C		C1		B1		B1
Original Par			$ 8,000	$ 1,000		$ 1,000		$ 1,000		$ 1,000		$ 3,000		$ 1,000
Book Value	280,689	276,326	6,744	904		823		917		710		2,890		500
Fair Value	284,271	281,197	2,465	379		230		219		208		1,223		206
Unrealized Loss			4,279	525		593		698		502		1,667		294
Recognized Losses
Lowest Rating				B+		Ca		Ca		C		Caa1		Ca
Number of Banks/Insurance Companies Currently Performing				44		40		48		34		30		28
Actual Deferrals/Defaults (as % of original collateral)				16.64%		34.94%		29.43%		26.61%		15.90%		27.94%
Total Projected Defaults (as % of performing collateral)				15.38%	[1]	27.67%	[1]	16.14%	[1]	22.84%	[1]	14.84%	[1]	16.86%	[1]
Excess Subordination (after taking into account best estimate of future deferrals/defaults				44.11%	[2]	0.84%	[2]	1.73%	[2]	6.09%	[2]	1.55%	[2]	0.00%	[2]

[1] A 10% recovery is applied to all projected defaults. A 15% recovery is applied to all projected insurance defaults. No recovery is applied to current defaults.

[2] Excess subordination represents the additional defaults in excess of both current and projected defaults that the CDO can absorb before the bond experiences any credit impairment. Excess subordinated percentage is calculated by (a) determining what percentage of defaults a deal can experience before the bond has credit impairment, and (b) subtracting from this default breakage percentage both total current and expected future default percentages.