LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Receivables Related Risk Rating Including Purchased Impaired Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	$ 12,306,997	$ 9,716,207
Construction and Land Development
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,201,149	1,194,821
Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,979,052	1,337,345
Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,198,580	2,467,410
Multifamily Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	659,946	548,231
Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	2,058,133	1,317,135
Residential 1-4 Family - Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	721,185	640,419
Residential 1-4 Family - Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	913,245	673,909
Auto
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	328,456	301,943
HELOC
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	660,963	613,383
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	386,848	379,694
Other Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	199,440	241,917
Purchased Impaired
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	89,735	90,221
Purchased Impaired | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	33,917	35,658
Purchased Impaired | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	28,736	21,699
Purchased Impaired | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	27,082	32,864
Purchased Impaired | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Construction and Land Development
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	8,387	8,654
Purchased Impaired | Construction and Land Development | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,233	1,835
Purchased Impaired | Construction and Land Development | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,993	1,308
Purchased Impaired | Construction and Land Development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,161	5,511
Purchased Impaired | Construction and Land Development | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	27,817	25,644
Purchased Impaired | Commercial Real Estate - Owner Occupied | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	8,273	8,347
Purchased Impaired | Commercial Real Estate - Owner Occupied | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	10,845	6,685
Purchased Impaired | Commercial Real Estate - Owner Occupied | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	8,699	10,612
Purchased Impaired | Commercial Real Estate - Owner Occupied | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	17,285	17,335
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,855	4,789
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	9,533	7,992
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,897	4,554
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Multifamily Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	93	88
Purchased Impaired | Multifamily Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Multifamily Real Estate | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	93	88
Purchased Impaired | Multifamily Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Multifamily Real Estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,262	2,156
Purchased Impaired | Commercial & Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	115	762
Purchased Impaired | Commercial & Industrial | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	57	134
Purchased Impaired | Commercial & Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,090	1,260
Purchased Impaired | Commercial & Industrial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Residential 1-4 Family - Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	12,237	13,601
Purchased Impaired | Residential 1-4 Family - Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	6,490	6,476
Purchased Impaired | Residential 1-4 Family - Commercial | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	2,780	2,771
Purchased Impaired | Residential 1-4 Family - Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	2,967	4,354
Purchased Impaired | Residential 1-4 Family - Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Residential 1-4 Family - Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	14,977	16,872
Purchased Impaired | Residential 1-4 Family - Consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	10,074	9,930
Purchased Impaired | Residential 1-4 Family - Consumer | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	233	1,030
Purchased Impaired | Residential 1-4 Family - Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	4,670	5,912
Purchased Impaired | Residential 1-4 Family - Consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Auto
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	7	7
Purchased Impaired | Auto | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3	7
Purchased Impaired | Auto | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Auto | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	4	0
Purchased Impaired | Auto | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | HELOC
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	4,275	5,115
Purchased Impaired | HELOC | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,092	3,438
Purchased Impaired | HELOC | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	607	1,031
Purchased Impaired | HELOC | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	576	646
Purchased Impaired | HELOC | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	682	32
Purchased Impaired | Consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	660	17
Purchased Impaired | Consumer | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	4	0
Purchased Impaired | Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	18	15
Purchased Impaired | Consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Other Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	713	717
Purchased Impaired | Other Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	122	57
Purchased Impaired | Other Commercial | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	591	660
Purchased Impaired | Other Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Other Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	$ 0	$ 0