Covered Loans - Composition of Covered Loans by Lending Classification (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Covered Loans [Line Items]
Covered loans	$ 288,577	$ 372,333	$ 489,331
Allowance for loan losses	(5,428)
Covered loans, net	283,149
Commercial Loans [Member]
Covered Loans [Line Items]
Covered loans	39,321
Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	130,683
Residential [Member]
Covered Loans [Line Items]
Covered loans	31,960
Consumer Portfolio Segment [Member]
Covered Loans [Line Items]
Covered loans	86,613
Covered Loans [Member]
Covered Loans [Line Items]
Covered loans	288,577
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member]
Covered Loans [Line Items]
Allowance for loan losses	(5,428)
Covered loans, net	174,979
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Commercial Loans [Member]
Covered Loans [Line Items]
Covered loans	16,925
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	110,785
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Residential [Member]
Covered Loans [Line Items]
Covered loans	31,804
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Consumer Portfolio Segment [Member]
Covered Loans [Line Items]
Covered loans	20,893
Loans Accounted For Under ASC 310-30 (Purchased Credit Impaired) [Member] | Covered Loans [Member]
Covered Loans [Line Items]
Covered loans	180,407
Not Purchased Credit Impaired [Member]
Covered Loans [Line Items]
Covered loans, net	108,170
Not Purchased Credit Impaired [Member] | Commercial Loans [Member]
Covered Loans [Line Items]
Covered loans	22,396
Not Purchased Credit Impaired [Member] | Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	19,898
Not Purchased Credit Impaired [Member] | Residential [Member]
Covered Loans [Line Items]
Covered loans	156
Not Purchased Credit Impaired [Member] | Consumer Portfolio Segment [Member]
Covered Loans [Line Items]
Covered loans	65,720
Not Purchased Credit Impaired [Member] | Covered Loans [Member]
Covered Loans [Line Items]
Covered loans	$ 108,170