Covered Loans - Composition of Covered Loans by Lending Classification (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Covered Loans [Line Items]
Covered loans	$ 250,801	$ 372,333	$ 448,789
Allowance for loan losses	(5,012)
Covered loans, net	245,789
Commercial Loans [Member]
Covered Loans [Line Items]
Covered loans	35,304
Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	103,536
Residential [Member]
Covered Loans [Line Items]
Covered loans	30,146
Consumer [Member]
Covered Loans [Line Items]
Covered loans	81,815
Covered Loans [Member]
Covered Loans [Line Items]
Covered loans	250,801
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member]
Covered Loans [Line Items]
Allowance for loan losses	(5,012)
Covered loans, net	147,818
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Commercial Loans [Member]
Covered Loans [Line Items]
Covered loans	14,818
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	88,526
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Residential [Member]
Covered Loans [Line Items]
Covered loans	30,009
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Consumer [Member]
Covered Loans [Line Items]
Covered loans	19,477
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Covered Loans [Member]
Covered Loans [Line Items]
Covered loans	152,830
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member]
Covered Loans [Line Items]
Covered loans, net	97,971
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Commercial Loans [Member]
Covered Loans [Line Items]
Covered loans	20,486
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	15,010
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Residential [Member]
Covered Loans [Line Items]
Covered loans	137
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Consumer [Member]
Covered Loans [Line Items]
Covered loans	62,338
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Covered Loans [Member]
Covered Loans [Line Items]
Covered loans	$ 97,971