Fair Value Disclosures (Quantitative Information about Level 3 Fair Value Measurements) (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Non-Agency Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 4,087	[1]
Valuation Technique(s)	Discounted cash flow	[1]
Conditional repayment rate	7.40%
Loss severity	45.00%
Conditional default rate	4.70%
Other Structured Financial Products [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	8,392
Valuation Technique(s)	Discounted cash flow
Credit default rates, call options and deferrals, waterfall structure, and covenants.	Varies by individual security
Other Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,160
Valuation Technique(s)	Discounted cash flow
Price to Book Multiple	0.9
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
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
Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	69,756
Valuation Technique(s)	Discounted cash flow
Timing of cash flows based upon current discount rates and terminal value	4.70%
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	3.30%
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	5.80%
Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 28,641
Valuation Technique(s)	Discounted cash flow
Third party appraisals less estimated selling costs	25.40%
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%
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%

[1] Consists of single security