Loans - Summary of Troubled Debt Restructurings Included in Covered Loans by Types of Concessions Made (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014 Contract	Dec. 31, 2013 Contract	Jun. 30, 2013 Contract	Jun. 30, 2012 Contract
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 21,100	$ 20,900	$ 20,600
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	9,221	8,409	10,253
Covered Loans [Member] | Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	87	76	70	70
Troubled debt restructuring loans	9,221	8,409	10,253	10,253
Covered Loans [Member] | Accruing Loans [Member] | Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts			4
Troubled debt restructuring loans			260
Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	78	68	57
Troubled debt restructuring loans	7,835	7,510	9,051
Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction, Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	3	4
Troubled debt restructuring loans	88	88	129
Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	6	5	5
Troubled debt restructuring loans	1,298	811	813
Covered Loans [Member] | Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	12	11	4	4
Troubled debt restructuring loans	597	686	151	151
Covered Loans [Member] | Non-Accruing Loans [Member] | Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1		1
Troubled debt restructuring loans	24		11
Covered Loans [Member] | Non-Accruing Loans [Member] | Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	26
Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	6	6	3
Troubled debt restructuring loans	374	457	140
Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction, Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	4
Troubled debt restructuring loans	45	96
Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	$ 128	$ 133