Covered Loans - Composition of Covered Loans by Lending Classification (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Covered Loans [Line Items]
Covered loans	$ 135,407	$ 147,708	$ 171,148
Allowance for loan losses	(1,712)	$ (3,552)	$ (3,658)
Covered loans, net	133,695
Commercial Loan [Member]
Covered Loans [Line Items]
Covered loans	12,958
Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	38,910
Residential [Member]
Covered Loans [Line Items]
Covered loans	19,281
Consumer Loan [Member]
Covered Loans [Line Items]
Covered loans	64,258
Loans Accounted for Under ASC 310-30 (Purchased Credit Impaired) [Member]
Covered Loans [Line Items]
Covered loans	65,538
Allowance for loan losses	(659)
Covered loans, net	64,879
Loans Accounted for Under ASC 310-30 (Purchased Credit Impaired) [Member] | Commercial Loan [Member]
Covered Loans [Line Items]
Covered loans	4,355
Loans Accounted for Under ASC 310-30 (Purchased Credit Impaired) [Member] | Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	31,538
Loans Accounted for Under ASC 310-30 (Purchased Credit Impaired) [Member] | Residential [Member]
Covered Loans [Line Items]
Covered loans	19,129
Loans Accounted for Under ASC 310-30 (Purchased Credit Impaired) [Member] | Consumer Loan [Member]
Covered Loans [Line Items]
Covered loans	10,516
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member]
Covered Loans [Line Items]
Covered loans	69,869
Allowance for loan losses	(1,053)
Covered loans, net	68,816
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Commercial Loan [Member]
Covered Loans [Line Items]
Covered loans	8,603
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Commercial Real Estate Loan [Member]
Covered Loans [Line Items]
Covered loans	7,372
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Residential [Member]
Covered Loans [Line Items]
Covered loans	152
Loans Excluded from ASC 310-30 (1) (Not Purchased Credit Impaired) [Member] | Consumer Loan [Member]
Covered Loans [Line Items]
Covered loans	$ 53,742