Fair Value Disclosures (Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 38,726		$ 31,348		$ 39,506		$ 16,723
Other-than-temporary impairment	(97)	[1]	3,092	[1]	(485)	[1]	2,948	[1]
Included in other comprehensive income (before taxes)	(754)		251		(1,146)		(5,117)
Sales			(18,782)				1,355
Ending Balance	37,875		15,909		37,875		15,909
Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	3,157		3,190		3,156		3,430
Other-than-temporary impairment	(97)	[1]	0	[1]	(97)	[1]	(144)	[1]
Included in other comprehensive income (before taxes)	(240)		(31)		(239)		(127)
Sales			0				0
Ending Balance	2,820		3,159		2,820		3,159
Other Structured Financial Products [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	9,977		8,021		9,550		13,293
Other-than-temporary impairment	0	[1]	0	[1]	0	[1]	0	[1]
Included in other comprehensive income (before taxes)	529		441		956		(4,831)
Sales			0				0
Ending Balance	10,506		8,462		10,506		8,462
Non Agency Mortgage Backed Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	25,592		20,137		26,800		0
Other-than-temporary impairment	0	[1]	3,092	[1]	(388)	[1]	3,092	[1]
Included in other comprehensive income (before taxes)	(1,043)		(159)		(1,863)		(159)
Sales			(18,782)				1,355
Ending Balance	$ 24,549		$ 4,288		$ 24,549		$ 4,288

[1] Included in noninterest income, net realized gain on sale of securities.