LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Receivables Related Risk Rating Including Purchased Impaired Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	$ 9,411,598	$ 7,141,552
Construction and Land Development
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	1,178,054	948,791
Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	1,283,125	943,933
Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	2,427,251	1,713,659
Multifamily Real Estate
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	542,662	357,079
Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	1,154,583	612,023
Residential 1-4 Family - Commercial
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	719,798	612,395
Residential 1-4 Family - Mortgage
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	611,728	485,690
Auto
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	306,196	282,474
HELOC
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	612,116	537,521
Consumer and all other
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	576,085	647,987
Purchased Impaired
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	94,746	39,021
Purchased Impaired | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	29,667	19,017
Purchased Impaired | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	38,804	13,881
Purchased Impaired | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	26,275	5,435
Purchased Impaired | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	688
Purchased Impaired | Construction and Land Development
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	5,042	2,838
Purchased Impaired | Construction and Land Development | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	1,859	1,462
Purchased Impaired | Construction and Land Development | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	1,232	1,260
Purchased Impaired | Construction and Land Development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	1,951	116
Purchased Impaired | Construction and Land Development | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	25,896	14,790
Purchased Impaired | Commercial Real Estate - Owner Occupied | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	3,546	4,958
Purchased Impaired | Commercial Real Estate - Owner Occupied | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	16,571	7,486
Purchased Impaired | Commercial Real Estate - Owner Occupied | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	5,779	2,346
Purchased Impaired | Commercial Real Estate - Owner Occupied | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	21,575	6,610
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	3,541	3,920
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	13,438	1,394
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	4,596	1,296
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Multifamily Real Estate
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	86	80
Purchased Impaired | Multifamily Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Multifamily Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	86	80
Purchased Impaired | Multifamily Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Multifamily Real Estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	2,299	408
Purchased Impaired | Commercial & Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	839	85
Purchased Impaired | Commercial & Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	126	123
Purchased Impaired | Commercial & Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	1,334	200
Purchased Impaired | Commercial & Industrial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Residential 1-4 Family - Commercial
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	16,073	9,414
Purchased Impaired | Residential 1-4 Family - Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	5,704	5,234
Purchased Impaired | Residential 1-4 Family - Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	4,936	2,877
Purchased Impaired | Residential 1-4 Family - Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	5,433	1,303
Purchased Impaired | Residential 1-4 Family - Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	0
Purchased Impaired | Residential 1-4 Family - Mortgage
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	16,761	3,733
Purchased Impaired | Residential 1-4 Family - Mortgage | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	9,735	2,764
Purchased Impaired | Residential 1-4 Family - Mortgage | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	830	329
Purchased Impaired | Residential 1-4 Family - Mortgage | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	6,196	71
Purchased Impaired | Residential 1-4 Family - Mortgage | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	569
Purchased Impaired | Auto
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	9	0
Purchased Impaired | Auto | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	9
Purchased Impaired | Auto | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0
Purchased Impaired | Auto | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0
Purchased Impaired | Auto | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0
Purchased Impaired | HELOC
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	6,179	950
Purchased Impaired | HELOC | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	4,354	446
Purchased Impaired | HELOC | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	893	291
Purchased Impaired | HELOC | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	932	94
Purchased Impaired | HELOC | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	0	119
Purchased Impaired | Consumer and all other
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	826	198
Purchased Impaired | Consumer and all other | Pass
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	80	148
Purchased Impaired | Consumer and all other | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	692	41
Purchased Impaired | Consumer and all other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	54	9
Purchased Impaired | Consumer and all other | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Net loans held for investment	$ 0	$ 0