Impairment of Investment Securities - Pooled Trust Preferred Collateralized Debt Obligations (Detail) (USD $) In Thousands, unless otherwise specified			9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member]	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL IV [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL V [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL VII [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL VIII [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL IX [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL X [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL XII [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL XIII [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL XIV [Member] Bank	Sep. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] MMCap I [Member] Bank
Impairment Of Investment Securities [Line Items]
Book Value			$ 41,971	$ 1,830	$ 59	$ 2,723	$ 1,956	$ 2,331	$ 1,469	$ 5,484	$ 12,403	$ 13,277	$ 439
Securities available for sale, at fair value	1,332,774	1,318,365	29,456	1,327	127	2,864	1,332	1,453	1,508	3,455	8,536	8,477	377
Unrealized Gain (Loss)			$ (12,515)	$ (503)	$ 68	$ 141	$ (624)	$ (878)	$ 39	$ (2,029)	$ (3,867)	$ (4,800)	$ (62)
Debt Instrument, Credit Rating				B1/BB	C/-	Ca/-	C/C	B3/C	Caa1/C	B3/C	Caa1/C	Caa1/C	Ca/C
Number of Banks (in banks)				6	3	14	29	40	45	66	58	56	11
Deferrals and Defaults as a % of Current Collateral				18.05%	100.00%	54.14%	59.12%	26.45%	31.95%	25.53%	20.94%	27.42%	59.24%
Excess Subordination as a % of Current Performing Collateral				41.28%	0.00%	0.00%	0.00%	2.23%	0.00%	0.00%	23.85%	43.02%	19.70%