Loans and Allowance for Loan Losses - Summary of Troubled Debt Restructuring by Concessions Made Types (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 23,900	$ 26,100
Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	55	39
Troubled debt restructuring loans	18,744	17,951
Accruing Loans [Member] | Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	1
Troubled debt restructuring loans	1,873	311
Accruing Loans [Member] | Forgiveness of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	2
Troubled debt restructuring loans	1,518	902
Accruing Loans [Member] | Payment Modification Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	1
Troubled debt restructuring loans	376	92
Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	11	7
Troubled debt restructuring loans	7,075	4,192
Accruing Loans [Member] | Rate Reduction, Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	18	14
Troubled debt restructuring loans	4,061	9,347
Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	18	14
Troubled debt restructuring loans	3,798	3,107
Accruing Loans [Member] | Rate Reduction, Payment Modification [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	43
Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	11
Troubled debt restructuring loans	5,171	8,155
Non-Accruing Loans [Member] | Forgiveness of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	372	136
Non-Accruing Loans [Member] | Payment Modification Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1
Troubled debt restructuring loans		307
Non-Accruing Loans [Member] | Rate Reduction Only [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	4
Troubled debt restructuring loans	177	1,145
Non-Accruing Loans [Member] | Rate Reduction, Forbearance of Interest [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2
Troubled debt restructuring loans	3,420
Non-Accruing Loans [Member] | Rate Reduction, Forbearance of Principal [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1
Troubled debt restructuring loans		1,123
Non-Accruing Loans [Member] | Rate Reduction, Payment Modification [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	4
Troubled debt restructuring loans	$ 1,202	$ 5,444