Impairment of Investment Securities - Pooled Trust Preferred Collateralized Debt Obligations (Detail) (USD $) In Thousands, unless otherwise specified			6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member]	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL IV [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL V [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL VII [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL VIII [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL IX [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL X [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL XII [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL XIII [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] Pre TSL XIV [Member] Bank	Jun. 30, 2014 Pooled Trust Preferred Collateralized Debt Obligations [Member] Mezzanine [Member] MMCap I [Member] Bank
Impairment Of Investment Securities [Line Items]
Book Value			$ 41,851	$ 1,830	$ 59	$ 2,691	$ 1,941	$ 2,322	$ 1,438	$ 5,446	$ 12,343	$ 13,344	$ 437
Securities available for sale, at fair value	1,347,611	1,318,365	28,154	1,294	109	2,626	1,281	1,380	1,497	3,289	8,103	8,196	379
Unrealized Gain (Loss)			$ (13,697)	$ (536)	$ 50	$ (65)	$ (660)	$ (942)	$ 59	$ (2,157)	$ (4,240)	$ (5,148)	$ (58)
Debt Instrument, Credit Rating				B1/BB	C/-	Ca/-	C/C	Caa1/C	Caa3/C	Caa3/C	Caa3/C	Ca/C	Ca/C
Number of Banks (in banks)				6	3	14	30	41	46	66	59	57	11
Deferrals and Defaults as a % of Current Collateral				18.05%	100.00%	52.23%	54.77%	28.47%	33.74%	25.87%	20.68%	26.73%	59.24%
Excess Subordination as a % of Current Performing Collateral				55.11%	0.00%	0.00%	0.00%	10.41%	0.00%	0.00%	12.85%	38.29%	34.51%