Credit Risk Profile By Internally Assigned Grade (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	$ 1,184,142	$ 1,277,090	$ 1,307,586
Commercial construction, land and land development
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	228,220	250,859
Commercial construction, land and land development | Excellent
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	265	281
Commercial construction, land and land development | Guideline
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	16,195	18,346
Commercial construction, land and land development | Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	21,569	21,721
Commercial construction, land and land development | Low Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	65,457	83,910
Commercial construction, land and land development | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	6,503	9,107
Commercial construction, land and land development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	118,231	117,494
Commercial construction, land and land development | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	0	0
Commercial construction, land and land development | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	0	0
Other commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	391,197	424,690
Other commercial real estate | Excellent
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	1,305	1,520
Other commercial real estate | Guideline
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	89,503	99,354
Other commercial real estate | Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	96,581	116,696
Other commercial real estate | Low Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	157,529	164,826
Other commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	14,876	12,996
Other commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	31,403	29,298
Other commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	0	0
Other commercial real estate | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	0	0
Residential Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	13,624	13,509
Residential Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	1,218	0
Residential Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	774	497
Residential Construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	0	0
Residential Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	11,632	13,012
Residential Mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	228,588	245,180
Residential Mortgage | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	9,832	8,841
Residential Mortgage | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	27,268	30,452
Residential Mortgage | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	158	187
Residential Mortgage | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	191,330	205,700
Commercial, financial and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	276,779	291,874	292,381
Commercial, financial and agricultural | Excellent
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	5,992	6,299
Commercial, financial and agricultural | Guideline
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	60,480	72,836
Commercial, financial and agricultural | Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	78,851	74,984
Commercial, financial and agricultural | Low Satisfactory
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	93,285	110,891
Commercial, financial and agricultural | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	24,456	14,833
Commercial, financial and agricultural | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	13,715	12,031
Commercial, financial and agricultural | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	0	0
Commercial, financial and agricultural | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	$ 0	$ 0