LOANS - Summary of the Company's Loan Portfolio by Credit Quality Indicator (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 1,258,779	$ 893,426	$ 745,441
Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,249,968	889,142
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,105	580
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,706	3,704
Mortgage loans on real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,047,074	699,624
Mortgage loans on real estate | Construction and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	157,667	90,737	81,863
Mortgage loans on real estate | 1-4 Family
Financing Receivable, Recorded Investment [Line Items]
Total loans	276,922	177,205	156,300
Mortgage loans on real estate | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Total loans	51,283	42,759	29,694
Mortgage loans on real estate | Farmland
Financing Receivable, Recorded Investment [Line Items]
Total loans	23,838	8,207	2,955
Mortgage loans on real estate | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	537,364	380,716	288,583
Mortgage loans on real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,040,512	699,011
Mortgage loans on real estate | Pass | Construction and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	157,385	90,238
Mortgage loans on real estate | Pass | 1-4 Family
Financing Receivable, Recorded Investment [Line Items]
Total loans	275,492	177,091
Mortgage loans on real estate | Pass | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Total loans	51,283	42,759
Mortgage loans on real estate | Pass | Farmland
Financing Receivable, Recorded Investment [Line Items]
Total loans	19,611	8,207
Mortgage loans on real estate | Pass | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	536,741	380,716
Mortgage loans on real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,847	20
Mortgage loans on real estate | Special Mention | Construction and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Mortgage loans on real estate | Special Mention | 1-4 Family
Financing Receivable, Recorded Investment [Line Items]
Total loans	74	20
Mortgage loans on real estate | Special Mention | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Mortgage loans on real estate | Special Mention | Farmland
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,773	0
Mortgage loans on real estate | Special Mention | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Mortgage loans on real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,715	593
Mortgage loans on real estate | Substandard | Construction and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	282	499
Mortgage loans on real estate | Substandard | 1-4 Family
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,356	94
Mortgage loans on real estate | Substandard | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Mortgage loans on real estate | Substandard | Farmland
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,454	0
Mortgage loans on real estate | Substandard | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	623	0
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	135,392	85,377	69,961
Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	134,522	83,215
Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	59
Commercial and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	870	2,103
Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	76,313	108,425	$ 116,085
Consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,934	106,916
Consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	258	501
Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 1,121	$ 1,008