Summary of Troubled Debt Restructurings and Subsequent Defaults (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
Financing Receivable, Modifications [Line Items]
Modification	$ 2,567	$ 4,664
Troubled Debt Restructurings, Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	613	2,486
Troubled Debt Restructurings, Rate Modifications
Financing Receivable, Modifications [Line Items]
Modification	258	258
Troubled Debt Restructurings, Rate and Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	1,696	1,920
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Modification	31	269
Commercial and industrial | Troubled Debt Restructurings, Term Modifications
Financing Receivable, Modifications [Line Items]
Modification		238
Commercial and industrial | Troubled Debt Restructurings, Rate and Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	31	31
Construction
Financing Receivable, Modifications [Line Items]
Modification	346	346
Construction | Troubled Debt Restructurings, Rate and Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	346	346
Commercial and farm land
Financing Receivable, Modifications [Line Items]
Modification	681	2,316
Commercial and farm land | Troubled Debt Restructurings, Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	82	1,717
Commercial and farm land | Troubled Debt Restructurings, Rate and Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	599	599
Residential
Financing Receivable, Modifications [Line Items]
Modification	1,509	1,733
Residential | Troubled Debt Restructurings, Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	531	531
Residential | Troubled Debt Restructurings, Rate Modifications
Financing Receivable, Modifications [Line Items]
Modification	258	258
Residential | Troubled Debt Restructurings, Rate and Term Modifications
Financing Receivable, Modifications [Line Items]
Modification	$ 720	$ 944