Loans and Allowance for Credit Losses - Troubled Debt Restructurings Identified During Period (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Contract	Jun. 30, 2013 Contract	Jun. 30, 2014 Contract	Jun. 30, 2013 Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts	13	16	34	32
Extend Maturity	$ 1,420	$ 373	$ 1,480	$ 806
Modify Rate	162	123	364	604
Modify Payments	133	772	683	1,302
Total Pre-Modification Outstanding Recorded Investment	1,715	1,268	2,527	2,712
Post- Modification Outstanding Recorded Investment	1,718	1,241	2,450	2,539
Financing Receivable Specific Reserve				662
Specific Reserve	2000	662000	68000
Commercial, financial, agricultural and other [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	1	1	2	3
Extend Maturity	1,420	100	1,480	526
Modify Rate	0	0	0	0
Modify Payments	0	0	0	12
Total Pre-Modification Outstanding Recorded Investment	1,420	100	1,480	538
Post- Modification Outstanding Recorded Investment	1,433	100	1,463	472
Financing Receivable Specific Reserve				100
Specific Reserve	0	100	20
Residential real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	8	13	21	22
Extend Maturity	0	273	0	280
Modify Rate	120	113	291	326
Modify Payments	126	769	644	1,284
Total Pre-Modification Outstanding Recorded Investment	246	1,155	935	1,890
Post- Modification Outstanding Recorded Investment	243	1,132	895	1,801
Financing Receivable Specific Reserve				562
Specific Reserve	2	562	48
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts			1	1
Extend Maturity			0	0
Modify Rate			0	244
Modify Payments			12	0
Total Pre-Modification Outstanding Recorded Investment			12	244
Post- Modification Outstanding Recorded Investment			7	237
Specific Reserve			0	0
Loans to individuals [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	4		10	6
Extend Maturity	0		0	0
Modify Rate	42		73	34
Modify Payments	7		27	6
Total Pre-Modification Outstanding Recorded Investment	49		100	40
Post- Modification Outstanding Recorded Investment	42		85	29
Financing Receivable Specific Reserve				$ 0
Specific Reserve	0		0