Loans - Summary of Credit Quality Indicate Financial Receivable (Non-Covered Loan Portfolio) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	$ 1,492,753	$ 1,450,635	$ 1,323,844
Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1,492,753	1,450,635	1,323,844
Non-Covered Loan [Member] | 10
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	40,268	32,993	26,454
Non-Covered Loan [Member] | 15
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	232,773	236,500	256,854
Non-Covered Loan [Member] | 20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	665,777	641,950	495,252
Non-Covered Loan [Member] | 23
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	29,403	31,433	29,631
Non-Covered Loan [Member] | 25
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	425,646	399,210	387,133
Non-Covered Loan [Member] | 30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	32,485	35,298	42,329
Non-Covered Loan [Member] | 40
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	66,147	72,994	85,666
Non-Covered Loan [Member] | 50
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	254	257	522
Non-Covered Loan [Member] | 60
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade			3
Commercial, financial & agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	180,888	174,217	149,320
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	180,888	174,217	149,320
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 10
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	32,223	24,623	18,767
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 15
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	11,569	11,316	14,063
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	75,503	79,522	63,200
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 23
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	45	42	265
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 25
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	52,631	49,071	44,035
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	3,324	2,343	3,148
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 40
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	5,494	7,200	5,716
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 50
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	99	100	123
Commercial, financial & agricultural [Member] | Non-Covered Loan [Member] | 60
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade			3
Real estate - construction & development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	130,161	114,199	122,331
Real estate - construction & development [Member] | Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	130,161	114,199	122,331
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 10
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade			19
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 15
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	4,794	4,373	5,402
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	34,947	31,413	33,805
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 23
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	6,606	8,521	8,458
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 25
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	66,012	52,577	58,943
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	6,004	3,394	1,955
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 40
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	11,643	13,765	13,459
Real estate - construction & development [Member] | Non-Covered Loan [Member] | 50
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	155	156	290
Real estate - commercial & farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	766,227	732,322	658,054
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	766,227	732,322	658,054
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member] | 10
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	304	309	211
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member] | 15
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	146,563	147,966	155,568
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member] | 20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	385,984	351,997	269,746
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member] | 23
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	8,970	9,012	9,188
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member] | 25
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	187,567	176,395	164,642
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member] | 30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	12,334	19,401	20,551
Real estate - commercial & farmland [Member] | Non-Covered Loan [Member] | 40
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	24,505	27,242	38,148
Real estate - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	355,716	346,480	328,053
Real estate - residential [Member] | Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	355,716	346,480	328,053
Real estate - residential [Member] | Non-Covered Loan [Member] | 10
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	500	464	415
Real estate - residential [Member] | Non-Covered Loan [Member] | 15
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	68,212	71,254	80,623
Real estate - residential [Member] | Non-Covered Loan [Member] | 20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	127,294	114,418	85,022
Real estate - residential [Member] | Non-Covered Loan [Member] | 23
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	13,662	13,788	11,719
Real estate - residential [Member] | Non-Covered Loan [Member] | 25
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	112,096	113,591	107,530
Real estate - residential [Member] | Non-Covered Loan [Member] | 30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	10,573	9,672	16,135
Real estate - residential [Member] | Non-Covered Loan [Member] | 40
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	23,379	23,292	26,515
Real estate - residential [Member] | Non-Covered Loan [Member] | 50
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade		1	94
Consumer installment loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	37,335	40,178	42,085
Consumer installment loans [Member] | Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	37,335	40,178	42,085
Consumer installment loans [Member] | Non-Covered Loan [Member] | 10
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	7,241	7,597	7,042
Consumer installment loans [Member] | Non-Covered Loan [Member] | 15
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1,635	1,591	1,198
Consumer installment loans [Member] | Non-Covered Loan [Member] | 20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	19,623	21,361	19,478
Consumer installment loans [Member] | Non-Covered Loan [Member] | 23
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	120	70	1
Consumer installment loans [Member] | Non-Covered Loan [Member] | 25
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	7,340	7,576	11,983
Consumer installment loans [Member] | Non-Covered Loan [Member] | 30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	250	488	540
Consumer installment loans [Member] | Non-Covered Loan [Member] | 40
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1,126	1,495	1,828
Consumer installment loans [Member] | Non-Covered Loan [Member] | 50
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade			15
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	22,426	43,239	24,001
Other [Member] | Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	22,426	43,239	24,001
Other [Member] | Non-Covered Loan [Member] | 20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	$ 22,426	$ 43,239	$ 24,001