Loans and Leases - Reserve for Loan and Lease Losses and Recorded Investment in Loans and Leases (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	$ 1,144			$ 230
Ending balance: collectively evaluated for impairment	22,950			24,488
Total ending balance	24,094	24,567	24,494	24,718	25,222	24,746
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	52,424			38,554
Ending balance: collectively evaluated for impairment	1,534,570			1,461,439
Total ending balance	1,586,994		1,541,484	1,499,993
Commercial, Financial and Agricultural [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	680			230
Ending balance: collectively evaluated for impairment	9,034			11,165
Total ending balance	9,714	9,547	9,789	11,395	11,883	11,594
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	14,800			3,146
Ending balance: collectively evaluated for impairment	433,193			436,761
Total ending balance	447,993		422,816	439,907
Real Estate-Commercial and Construction [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	8
Ending balance: collectively evaluated for impairment	9,255			8,662
Total ending balance	9,263	9,247	8,780	8,662	8,032	7,507
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	34,259			34,471
Ending balance: collectively evaluated for impairment	668,536			629,956
Total ending balance	702,795			664,427
Real Estate-Residential Secured for Business Purpose [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	456
Ending balance: collectively evaluated for impairment	569			586
Total ending balance	1,025	1,056	1,062	586	570	639
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	2,477			169
Ending balance: collectively evaluated for impairment	32,807			32,160
Total ending balance	35,284		37,319	32,329
Real Estate-Residential and Home Equity Secured for Personal Purpose [Member]
Reserve for loan and lease losses:
Ending balance: collectively evaluated for impairment	1,248			1,084
Total ending balance	1,248	1,221	1,284	1,084	792	980
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	887			730
Ending balance: collectively evaluated for impairment	260,345			227,381
Total ending balance	261,232			228,111
Loans to Individuals [Member]
Reserve for loan and lease losses:
Ending balance: collectively evaluated for impairment	405			693
Total ending balance	405	598	694	693	628	679
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	1			38
Ending balance: collectively evaluated for impairment	31,563			43,560
Total ending balance	31,564		40,000	43,598
Lease Financings [Member]
Reserve for loan and lease losses:
Ending balance: collectively evaluated for impairment	1,101			1,212
Total ending balance	1,101	1,295	1,285	1,212	1,358	1,326
Loans and leases held for investment:
Ending balance: collectively evaluated for impairment	108,126			91,621
Total ending balance	108,126		105,994	91,621
Unallocated [Member]
Reserve for loan and lease losses:
Ending balance: collectively evaluated for impairment	1,338			1,086
Total ending balance	$ 1,338	$ 1,603	$ 1,600	$ 1,086	$ 1,959	$ 2,021