Loans and Allowance for Credit Losses - Troubled Debt Restructurings Identified During Period (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 Contract	Dec. 31, 2013 Contract	Dec. 31, 2012 Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts	77	82	60
Extend Maturity	$ 5,487	$ 4,390	$ 6,776
Modify Rate	732	2,018	4,724
Modify Payments	16,381	3,971	10,332
Others		0	54
Total Pre-Modification Outstanding Recorded Investment	22,600	10,379	21,886
Post-Modification Outstanding Recorded Investment	15,967	7,713	22,221
Specific Reserve	4,665	1,101	4,915
Commercial, financial, agricultural and other [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	9	14	12
Extend Maturity	5,487	3,462	1,599
Modify Rate	0	0	187
Modify Payments	14,529	1,677	9,476
Others		0	0
Total Pre-Modification Outstanding Recorded Investment	20,016	5,139	11,262
Post-Modification Outstanding Recorded Investment	13,785	3,104	11,335
Specific Reserve	4,665	906	4,237
Real estate construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts			2
Extend Maturity			1,697
Modify Rate			0
Modify Payments			0
Others			0
Total Pre-Modification Outstanding Recorded Investment			1,697
Post-Modification Outstanding Recorded Investment			2,133
Specific Reserve			200
Residential real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	52	46	25
Extend Maturity	0	347	200
Modify Rate	629	418	132
Modify Payments	1,797	2,116	697
Others		0	48
Total Pre-Modification Outstanding Recorded Investment	2,426	2,881	1,077
Post-Modification Outstanding Recorded Investment	2,062	2,316	973
Specific Reserve	0	161	69
Commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	1	5	4
Extend Maturity	0	571	3,280
Modify Rate	0	1,499	4,308
Modify Payments	8	145	71
Others		0	0
Total Pre-Modification Outstanding Recorded Investment	8	2,215	7,659
Post-Modification Outstanding Recorded Investment	6	2,184	7,607
Specific Reserve	0	34	409
Loans to individuals [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	15	17	17
Extend Maturity	0	10	0
Modify Rate	103	101	97
Modify Payments	47	33	88
Others		0	6
Total Pre-Modification Outstanding Recorded Investment	150	144	191
Post-Modification Outstanding Recorded Investment	114	109	173
Specific Reserve	$ 0	$ 0	$ 0

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Specific reserve related to troubled debt restructurings identified during the period.

+ References

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

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The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

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-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

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