Basis of Presentation and Accounting Policies - Valuation Methodologies for Instruments Measured at Fair Value on Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	$ 931,555	$ 965,056	$ 630,223
Impaired Loans Carried at Fair Value [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	41,253	42,546	51,150
Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	33,839	33,351	40,434
Purchased Non-Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	437,269	448,753
Purchased Non-Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	3,864	4,276
Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	372,694	390,237	460,724
Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	42,636	45,893	77,915
Level 1 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Impaired Loans Carried at Fair Value [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Purchased Non-Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Purchased Non-Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 1 [Member] | Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 2 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Impaired Loans Carried at Fair Value [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Purchased Non-Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Purchased Non-Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 2 [Member] | Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value
Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	931,555	965,056	630,223
Level 3 [Member] | Impaired Loans Carried at Fair Value [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	41,253	42,546	51,150
Level 3 [Member] | Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	33,839	33,351	40,434
Level 3 [Member] | Purchased Non-Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	437,269	448,753
Level 3 [Member] | Purchased Non-Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	3,864	4,276
Level 3 [Member] | Covered Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	372,694	390,237	460,724
Level 3 [Member] | Covered Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Nonrecurring assets at fair value	$ 42,636	$ 45,893	$ 77,915