Loans - Summary of Troubled Debt Restructurings, Excluding Purchased Non-Covered and Covered Loans, by Concessions Made Types (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 21,100	$ 20,900	$ 20,600
Excluding Purchased Non-Covered and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	17,337	17,214	18,015
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	86	72	61
Troubled debt restructuring loans	17,337	17,214	18,015
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	12	10	9
Troubled debt restructuring loans	2,145	2,170	2,168
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Forgiveness of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	3	3
Troubled debt restructuring loans	2,448	1,467	1,493
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Payment Modification Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1	2
Troubled debt restructuring loans		280	373
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	14	14	12
Troubled debt restructuring loans	6,842	7,069	6,924
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction, Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	38	26	18
Troubled debt restructuring loans	3,204	3,252	4,724
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	17	18	17
Troubled debt restructuring loans	2,698	2,976	2,333
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	22	20	9
Troubled debt restructuring loans	3,743	3,683	2,568
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		2	2
Troubled debt restructuring loans		97	105
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Forgiveness of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1	1
Troubled debt restructuring loans		145	145
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Payment Modification Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1
Troubled debt restructuring loans		88
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	3	2
Troubled debt restructuring loans	1,176	913	496
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction, Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	14	12	1
Troubled debt restructuring loans	2,522	2,411	222
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2		2
Troubled debt restructuring loans	16		1,571
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Rate Reduction, Payment Modification [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1	1
Troubled debt restructuring loans	$ 29	$ 29	$ 29