Fair Value - Assets and Liabilities Measured on Non-Recurring Basis (Detail) - Non-Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Impaired Loans [Member] \| Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 232	$ 227
Impaired Loans [Member] \| Carrying Value [Member] \| Commercial, Financial and Agricultural [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	7
Impaired Loans [Member] \| Carrying Value [Member] \| Residential Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	19	21
Impaired Loans [Member] \| Carrying Value [Member] \| Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	206	206
Other Real Estate Owned [Member] \| Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,062	4,697
Other Real Estate Owned [Member] \| Carrying Value [Member] \| Construction and Development [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,220	2,839
Other Real Estate Owned [Member] \| Carrying Value [Member] \| Non-Farm, Non-Residential [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	604	1,709
Other Real Estate Owned [Member] \| Carrying Value [Member] \| Residential Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	238	149
Level 3 [Member] \| Impaired Loans [Member] \| Commercial, Financial and Agricultural [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	7
Level 3 [Member] \| Impaired Loans [Member] \| Residential Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	19
Level 3 [Member] \| Impaired Loans [Member] \| Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	206
Level 3 [Member] \| Impaired Loans [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	232	227
Level 3 [Member] \| Impaired Loans [Member] \| Estimate of Fair Value Measurement [Member] \| Commercial, Financial and Agricultural [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	7
Level 3 [Member] \| Impaired Loans [Member] \| Estimate of Fair Value Measurement [Member] \| Residential Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	19	21
Level 3 [Member] \| Impaired Loans [Member] \| Estimate of Fair Value Measurement [Member] \| Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	206	206
Level 3 [Member] \| Other Real Estate Owned [Member] \| Construction and Development [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,220
Level 3 [Member] \| Other Real Estate Owned [Member] \| Non-Farm, Non-Residential [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	604
Level 3 [Member] \| Other Real Estate Owned [Member] \| Residential Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	238
Level 3 [Member] \| Other Real Estate Owned [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,062	4,697
Level 3 [Member] \| Other Real Estate Owned [Member] \| Estimate of Fair Value Measurement [Member] \| Construction and Development [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,220	2,839
Level 3 [Member] \| Other Real Estate Owned [Member] \| Estimate of Fair Value Measurement [Member] \| Non-Farm, Non-Residential [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	604	1,709
Level 3 [Member] \| Other Real Estate Owned [Member] \| Estimate of Fair Value Measurement [Member] \| Residential Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 238	$ 149

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