Fair Value of Financial Instruments - Summary of Fair Value Measurements of Assets Measured at Fair Value on Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	$ 688,349	$ 770,703
Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	52,514	70,296
Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	39,850	50,301
Covered Loan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	507,712	571,489
Covered Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	88,273	78,617
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Covered Loan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Covered Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Covered Loan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Covered Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	688,349	770,703
Level 3 [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	52,514	70,296
Level 3 [Member] | Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	39,850	50,301
Level 3 [Member] | Covered Loan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	507,712	571,489
Level 3 [Member] | Covered Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Nonrecurring assets at fair value	$ 88,273	$ 78,617