Loans - Summary of Non-Covered Past Due Financial Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	$ 27,400	$ 40,300
Total Loans	1,492,753	1,450,635	1,323,844
Non Covered Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	22,881	11,825	18,585
Loans 60-89 Days Past Due	6,795	6,097	9,856
Loans 90 or More Days Past Due	33,655	34,287	48,104
Total Loans Past Due	63,331	52,209	76,545
Current Loans	1,429,422	1,398,426	1,247,299
Total Loans	1,492,753	1,450,635	1,323,844
Loans 90 Days or More Past Due and Still Accruing
Commercial, financial & agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	180,888	174,217	149,320
Commercial, financial & agricultural [Member] | Non Covered Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	1,797	258	1,477
Loans 60-89 Days Past Due	149	312	291
Loans 90 or More Days Past Due	3,729	3,969	4,559
Total Loans Past Due	5,675	4,539	6,327
Current Loans	175,213	169,678	142,993
Total Loans	180,888	174,217	149,320
Loans 90 Days or More Past Due and Still Accruing
Real estate - construction & development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	130,161	114,199	122,331
Real estate - construction & development [Member] | Non Covered Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	1,538	347	2,356
Loans 60-89 Days Past Due	1,538	332	481
Loans 90 or More Days Past Due	8,312	8,969	9,531
Total Loans Past Due	11,388	9,648	12,368
Current Loans	118,773	104,551	109,963
Total Loans	130,161	114,199	122,331
Loans 90 Days or More Past Due and Still Accruing
Real estate - commercial & farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	766,227	732,322	658,054
Real estate - commercial & farmland [Member] | Non Covered Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	11,115	2,867	9,991
Loans 60-89 Days Past Due	3,220	2,296	2,412
Loans 90 or More Days Past Due	9,352	9,544	19,646
Total Loans Past Due	23,687	14,707	32,049
Current Loans	742,540	717,615	626,005
Total Loans	766,227	732,322	658,054
Loans 90 Days or More Past Due and Still Accruing
Real estate - residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	355,716	346,480	328,053
Real estate - residential [Member] | Non Covered Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	7,686	7,651	3,905
Loans 60-89 Days Past Due	1,719	2,766	6,175
Loans 90 or More Days Past Due	11,699	10,990	13,298
Total Loans Past Due	21,104	21,407	23,378
Current Loans	334,612	325,073	304,675
Total Loans	355,716	346,480	328,053
Loans 90 Days or More Past Due and Still Accruing
Consumer installment loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	37,335	40,178	42,085
Consumer installment loans [Member] | Non Covered Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	745	702	856
Loans 60-89 Days Past Due	169	391	497
Loans 90 or More Days Past Due	563	815	1,070
Total Loans Past Due	1,477	1,908	2,423
Current Loans	35,858	38,270	39,662
Total Loans	37,335	40,178	42,085
Loans 90 Days or More Past Due and Still Accruing
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	22,426	43,239	24,001
Other [Member] | Non Covered Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due
Loans 60-89 Days Past Due
Loans 90 or More Days Past Due
Total Loans Past Due
Current Loans	22,426	43,239	24,001
Total Loans	22,426	43,239	24,001
Loans 90 Days or More Past Due and Still Accruing