Investment in Loans Related to Each Segment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	$ 23,202	$ 23,749
Allowance for Loans Individually Evaluated	5,593	4,997
Loans Collectively Evaluated for Impairment	1,559,901	1,369,432
Allowance for Loans Collectively Evaluated	20,169	21,007
Acquired Impaired Loans Evaluated for Impairment	139,362	2,886
Allowance for Acquired Impaired Loans Evaluated	8	201
Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	17,753	15,418
Allowance for Loans Individually Evaluated	4,426	3,794
Loans Collectively Evaluated for Impairment	831,523	694,131
Allowance for Loans Collectively Evaluated	12,833	13,757
Acquired Impaired Loans Evaluated for Impairment	79,115	2,491
Allowance for Acquired Impaired Loans Evaluated	8	201
Commercial Loans | Construction Development And Other Land
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	2,916	773
Allowance for Loans Individually Evaluated		4
Loans Collectively Evaluated for Impairment	54,579	60,846
Allowance for Loans Collectively Evaluated	1,214	1,888
Acquired Impaired Loans Evaluated for Impairment	25,744	149
Commercial Loans | Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	3,602	3,738
Allowance for Loans Individually Evaluated	3,192	1,847
Loans Collectively Evaluated for Impairment	88,540	87,563
Allowance for Loans Collectively Evaluated	1,159	1,668
Acquired Impaired Loans Evaluated for Impairment	3,544	638
Allowance for Acquired Impaired Loans Evaluated	8	201
Commercial Loans | Multi-family Residential
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	378	278
Allowance for Loans Individually Evaluated	18
Loans Collectively Evaluated for Impairment	67,278	76,772
Allowance for Loans Collectively Evaluated	1,612	1,889
Acquired Impaired Loans Evaluated for Impairment	649
Commercial Loans | Single-family Non-owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	2,794	3,438
Allowance for Loans Individually Evaluated	858	124
Loans Collectively Evaluated for Impairment	134,323	102,063
Allowance for Loans Collectively Evaluated	3,509	2,836
Acquired Impaired Loans Evaluated for Impairment	10,223	1,242
Commercial Loans | Non-farm, Non-residential
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	8,063	6,933
Allowance for Loans Individually Evaluated	358	1,819
Loans Collectively Evaluated for Impairment	450,172	328,610
Allowance for Loans Collectively Evaluated	4,901	5,114
Acquired Impaired Loans Evaluated for Impairment	38,072	462
Commercial Loans | Agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans Collectively Evaluated for Impairment	1,852	1,374
Allowance for Loans Collectively Evaluated	22	19
Acquired Impaired Loans Evaluated for Impairment	1
Commercial Loans | Farmland Loan
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment		258
Loans Collectively Evaluated for Impairment	34,779	36,903
Allowance for Loans Collectively Evaluated	416	343
Acquired Impaired Loans Evaluated for Impairment	882
Consumer Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	5,449	8,325
Allowance for Loans Individually Evaluated	1,167	1,203
Loans Collectively Evaluated for Impairment	641,675	595,311
Allowance for Loans Collectively Evaluated	6,739	6,508
Acquired Impaired Loans Evaluated for Impairment	59,447	395
Consumer Real Estate | Home Equity Lines
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	499	368
Allowance for Loans Individually Evaluated	223
Loans Collectively Evaluated for Impairment	141,684	111,019
Allowance for Loans Collectively Evaluated	1,351	1,365
Acquired Impaired Loans Evaluated for Impairment	50,343
Consumer Real Estate | Single Family Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment	4,950	7,957
Allowance for Loans Individually Evaluated	944	1,203
Loans Collectively Evaluated for Impairment	483,223	464,715
Allowance for Loans Collectively Evaluated	5,051	4,931
Acquired Impaired Loans Evaluated for Impairment	8,005	395
Consumer Real Estate | Owner occupied construction
Financing Receivable, Recorded Investment [Line Items]
Loans Collectively Evaluated for Impairment	16,768	19,577
Allowance for Loans Collectively Evaluated	337	212
Acquired Impaired Loans Evaluated for Impairment	1,099
Consumer and Other
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment		6
Loans Collectively Evaluated for Impairment	86,703	79,990
Allowance for Loans Collectively Evaluated	597	742
Acquired Impaired Loans Evaluated for Impairment	800
Consumer and Other | Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Non-acquired Loans Individually Evaluated for Impairment		6
Loans Collectively Evaluated for Impairment	81,037	67,123
Allowance for Loans Collectively Evaluated	597	742
Acquired Impaired Loans Evaluated for Impairment	800
Consumer and Other | Other
Financing Receivable, Recorded Investment [Line Items]
Loans Collectively Evaluated for Impairment	$ 5,666	$ 12,867