Loans - Contractual Aging of Recorded Investment in Past Due Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing 30-59 Days Past Due	$ 1,759	$ 2,168
Accruing 60-89 Days Past Due	194	1,382
Accruing Greater Than 90 Days	0	1
Nonaccrual	28,724	40,955
Current	1,232,235	1,181,575
Total Financing Receivables	1,262,912	1,226,081
Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing 30-59 Days Past Due	86	7
Accruing 60-89 Days Past Due	0	0
Accruing Greater Than 90 Days	0	0
Nonaccrual	1,454	1,342
Current	61,226	59,387
Total Financing Receivables	62,766	60,736
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing 30-59 Days Past Due	21	832
Accruing 60-89 Days Past Due	0	5
Accruing Greater Than 90 Days	0	0
Nonaccrual	6,339	17,234
Current	492,710	468,757
Total Financing Receivables	499,070	486,828
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing 30-59 Days Past Due	1,575	1,179
Accruing 60-89 Days Past Due	194	1,377
Accruing Greater Than 90 Days	0	1
Nonaccrual	20,696	22,099
Current	560,111	544,675
Total Financing Receivables	582,576	569,331
Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing 30-59 Days Past Due	0	41
Accruing 60-89 Days Past Due	0	0
Accruing Greater Than 90 Days	0	0
Nonaccrual	0	0
Current	70,779	61,862
Total Financing Receivables	70,779	61,903
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing 30-59 Days Past Due	77	109
Accruing 60-89 Days Past Due	0	0
Accruing Greater Than 90 Days	0	0
Nonaccrual	235	280
Current	46,919	46,541
Total Financing Receivables	47,231	46,930
Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing 30-59 Days Past Due	0	0
Accruing 60-89 Days Past Due	0	0
Accruing Greater Than 90 Days	0	0
Nonaccrual	0	0
Current	490	353
Total Financing Receivables	$ 490	$ 353