Loans and Allowance for Credit Losses - Recorded Investment and Unpaid Principal Balance for Impaired Loans with Associated Allowance (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 59,383	$ 107,555
Unpaid Principal Balance	66,307	139,687
Related Allowance	8,824	17,778
Average Recorded Investment	78,175	87,979	139,922
Interest Income Recognized	679	369	1,393
Commercial, financial, agricultural and other with no related allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,752	8,080
Unpaid Principal Balance	7,649	8,983
Average Recorded Investment	14,454	9,217	3,887
Interest Income Recognized	73	173	20
Real estate construction with no related allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,486	8,491
Unpaid Principal Balance	6,664	35,555
Average Recorded Investment	5,923	11,912	23,254
Interest Income Recognized	47	0	10
Residential real estate with no related allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	9,333	7,928
Unpaid Principal Balance	9,952	8,401
Average Recorded Investment	9,280	8,114	2,702
Interest Income Recognized	211	72	9
Commercial real estate with no related allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,606	33,259
Unpaid Principal Balance	14,719	35,401
Average Recorded Investment	27,881	28,574	35,817
Interest Income Recognized	250	66	799
Loans to individuals with no related allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	289	256
Unpaid Principal Balance	307	256
Average Recorded Investment	255	103	10
Interest Income Recognized	3	2	0
Subtotal with no related allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	33,466	58,014
Unpaid Principal Balance	39,291	88,596
Average Recorded Investment	57,793	57,920	65,670
Interest Income Recognized	584	313	838
Commercial, financial, agricultural and other With an allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	21,482	26,532
Unpaid Principal Balance	22,082	27,412
Related Allowance	7,364	10,331
Average Recorded Investment	16,479	21,979	30,456
Interest Income Recognized	64	9	152
Real estate construction with an allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	414	2,756
Unpaid Principal Balance	737	3,087
Related Allowance	94	300
Average Recorded Investment	515	1,457	14,465
Interest Income Recognized	0	0	0
Residential real estate With an allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,533	2,695
Unpaid Principal Balance	3,585	2,696
Related Allowance	1,282	780
Average Recorded Investment	3,200	1,599	615
Interest Income Recognized	31	15	7
Commercial real estate With an allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	488	17,558
Unpaid Principal Balance	612	17,896
Related Allowance	84	6,367
Average Recorded Investment	188	5,024	28,716
Interest Income Recognized	0	32	396
Loans to individuals With an allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0	0
Interest Income Recognized	0	0	0
Subtotal With an allowance recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	25,917	49,541
Unpaid Principal Balance	27,016	51,091
Related Allowance	8,824	17,778
Average Recorded Investment	20,382	30,059	74,252
Interest Income Recognized	$ 95	$ 56	$ 555