Loans - Summary of Troubled Debt Restructurings, Excluding Purchased Non-Covered and Covered Loans, by Concessions Made Types (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 21,200	$ 20,900	$ 23,300
Excluding Purchased Non-Covered and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	18,848	17,214	18,513
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	80	72	52
Troubled debt restructuring loans	18,848	17,214	18,513
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	8	10	2
Troubled debt restructuring loans	1,933	2,170	1,843
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Forgiveness of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	4	3	3
Troubled debt restructuring loans	1,957	1,467	1,504
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	376
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	13	14	10
Troubled debt restructuring loans	6,782	7,069	7,033
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	17
Troubled debt restructuring loans	5,489	3,252	4,046
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	18
Troubled debt restructuring loans	2,687	2,976	3,711
Excluding Purchased Non-Covered and Covered Loans [Member] | Accruing Loans [Member] | Rate Reduction, Payment Modification [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts
Troubled debt restructuring loans
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	18	20	8
Troubled debt restructuring loans	2,365	3,683	4,755
Excluding Purchased Non-Covered and Covered Loans [Member] | Non-Accruing Loans [Member] | Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	4	2
Troubled debt restructuring loans	300	97
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	1
Troubled debt restructuring loans	516	145	207
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	1
Troubled debt restructuring loans	149	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	4	3	2
Troubled debt restructuring loans	1,134	913	182
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	6	12	2
Troubled debt restructuring loans	230	2,411	3,100
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	1		1
Troubled debt restructuring loans	7		255
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	2
Troubled debt restructuring loans	$ 29	$ 29	$ 1,011