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
	Mar. 31, 2013		Mar. 31, 2012
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 39,506		$ 16,723
Other-than-temporary impairment	(388)	[1]	(144)	[1]
Included in other comprehensive income (before taxes)	(392)		(5,368)
Transfers into Level III			20,137
Ending Balance	38,726		31,348
Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	3,156		3,430
Other-than-temporary impairment	0	[1]	(144)	[1]
Included in other comprehensive income (before taxes)	1		(96)
Transfers into Level III			0
Ending Balance	3,157		3,190
Other Structured Financial Products [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	9,550		13,293
Other-than-temporary impairment	0	[1]	0	[1]
Included in other comprehensive income (before taxes)	427		(5,272)
Transfers into Level III			0
Ending Balance	9,977		8,021
Non Agency Mortgage Backed Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	26,800		0
Other-than-temporary impairment	(388)	[1]	0	[1]
Included in other comprehensive income (before taxes)	(820)		0
Transfers into Level III			20,137
Ending Balance	$ 25,592		$ 20,137

[1] Included in noninterest income, net impairment losses recognized in earnings.