Fair Value Disclosures (Quantitative Information about Level 3 Fair Value Measurements) (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Non-Agency Residential Mortgage-Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 24,549	$ 26,800
Valuation Technique(s)	Discounted Cash Flow	Discounted Cash Flow
Conditional repayment rate	10.40%	10.40%
Loss severity	42.00%	43.80%
Conditional default rate	3.60%	3.60%
Other Structured Financial Products [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	10,506	9,550
Valuation Technique(s)	Discounted Cash Flow	Discounted Cash Flow
Credit default rates, call options and deferrals, waterfall structure, and covenants.	Varies by individual security, refer to Note 3	Varies by individual security, refer to Note 3
Other Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	2,820	3,156
Valuation Technique(s)	Discounted Cash Flow	Discounted Cash Flow
Other Equity Securities [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Price to book multiple	0.2	0.2
Other Equity Securities [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Price to book multiple	1.5	1.5
Other Equity Securities [Member] | Weighted Average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Price to book multiple	0.9	0.9
Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	80,085	65,731
Valuation Technique(s)	Discounted Cash Flow	Discounted Cash Flow
Impaired Loans [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Timing of cash flows based upon current discount rates and terminal value	1.10%	2.90%
Impaired Loans [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Timing of cash flows based upon current discount rates and terminal value	8.20%	5.60%
Impaired Loans [Member] | Weighted Average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Timing of cash flows based upon current discount rates and terminal value	4.00%	4.20%
Foreclosed Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 18,349	$ 26,245
Valuation Technique(s)	Discounted Cash Flow	Discounted Cash Flow
Foreclosed Assets [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Third party appraisals less estimated selling costs	0.00%	0.00%
Foreclosed Assets [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Third party appraisals less estimated selling costs	100.00%	100.00%
Foreclosed Assets [Member] | Weighted Average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Third party appraisals less estimated selling costs	27.40%	24.00%