Loans and Leases - Reserve for Loan and Lease Losses and Recorded Investment in Loans and Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	$ 235	$ 322
Ending balance: collectively evaluated for impairment	17,264	17,298
Ending balance: acquired credit impaired loans evaluated for impairment		8
Total ending balance	17,499	17,628	$ 20,662	$ 24,494
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	43,915	48,933
Ending balance: collectively evaluated for impairment	2,346,917	1,834,630
Loans measured at fair value	2,138
Acquired non-credit impaired loans	885,564	294,197
Acquired credit impaired loans	7,352	1,253
Total Loans and Leases Held for Investment	3,285,886	2,179,013
Commercial, Financial and Agricultural [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	19	208
Ending balance: collectively evaluated for impairment	7,018	6,210
Ending balance: acquired credit impaired loans evaluated for impairment		0
Total ending balance	7,037	6,418	6,920	9,789
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	11,077	12,881
Ending balance: collectively evaluated for impairment	652,144	467,099
Loans measured at fair value	0
Acquired non-credit impaired loans	159,456	24,218
Acquired credit impaired loans	589	317
Total Loans and Leases Held for Investment	823,266	504,515
Real Estate-Commercial and Construction [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	25	0
Ending balance: collectively evaluated for impairment	7,480	6,564
Ending balance: acquired credit impaired loans evaluated for impairment		8
Total ending balance	7,505	6,572	8,943	8,780
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	25,066	30,088
Ending balance: collectively evaluated for impairment	1,027,406	821,158
Loans measured at fair value	2,138
Acquired non-credit impaired loans	489,473	130,674
Acquired credit impaired loans	5,710	513
Total Loans and Leases Held for Investment	1,549,793	982,433
Real Estate-Residential Secured for Business Purpose [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	191	45
Ending balance: collectively evaluated for impairment	583	718
Ending balance: acquired credit impaired loans evaluated for impairment		0
Total ending balance	774	763	763	1,062
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	6,687	4,892
Ending balance: collectively evaluated for impairment	145,244	89,388
Loans measured at fair value	0
Acquired non-credit impaired loans	141,353	124,080
Acquired credit impaired loans	784	423
Total Loans and Leases Held for Investment	294,068	218,783
Real Estate-Residential and Home Equity Secured for Personal Purpose [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	0	69
Ending balance: collectively evaluated for impairment	993	1,506
Ending balance: acquired credit impaired loans evaluated for impairment		0
Total ending balance	993	1,575	1,124	1,284
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	1,085	1,072
Ending balance: collectively evaluated for impairment	357,274	302,139
Loans measured at fair value	0
Acquired non-credit impaired loans	95,019	14,899
Acquired credit impaired loans	269	0
Total Loans and Leases Held for Investment	453,647	318,110
Loans to Individuals [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	0	0
Ending balance: collectively evaluated for impairment	364	346
Ending balance: acquired credit impaired loans evaluated for impairment		0
Total ending balance	364	346	360	694
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	0	0
Ending balance: collectively evaluated for impairment	30,110	29,406
Loans measured at fair value	0
Acquired non-credit impaired loans	263	326
Acquired credit impaired loans	0	0
Total Loans and Leases Held for Investment	30,373	29,732
Lease Financings [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment	0	0
Ending balance: collectively evaluated for impairment	788	1,042
Ending balance: acquired credit impaired loans evaluated for impairment		0
Total ending balance	788	1,042	985	1,285
Loans and leases held for investment:
Ending balance: individually evaluated for impairment	0	0
Ending balance: collectively evaluated for impairment	134,739	125,440
Loans measured at fair value	0
Acquired non-credit impaired loans	0	0
Acquired credit impaired loans	0	0
Total Loans and Leases Held for Investment	134,739	125,440
Unallocated [Member]
Reserve for loan and lease losses:
Ending balance: collectively evaluated for impairment	38	912
Ending balance: acquired credit impaired loans evaluated for impairment		0
Total ending balance	$ 38	$ 912	$ 1,567	$ 1,600