LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Receivables Related Risk Rating Including Purchased Impaired Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	$ 11,952,310	$ 9,716,207
Construction and Land Development
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,326,679	1,194,821
Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,921,464	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	2,970,453	2,467,410
Multifamily Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	591,431	548,231
Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,866,625	1,317,135
Residential 1-4 Family - Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	815,309	713,750
Residential 1-4 Family - Mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	865,502	600,578
Auto
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	300,631	301,943
HELOC
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	672,087	613,383
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	397,491	379,694
Other Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	224,638	241,917
Purchased Impaired
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	99,932	90,221
Purchased Impaired | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	36,166	35,658
Purchased Impaired | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	26,110	21,699
Purchased Impaired | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	37,586	32,864
Purchased Impaired | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	70	0
Purchased Impaired | Construction and Land Development
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	12,600	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	1,760	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	4,430	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	6,410	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	26,836	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	8,194	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	6,741	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	11,901	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	18,850	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	4,596	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	7,323	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	6,931	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	90	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	90	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	4,159	2,156
Purchased Impaired | Commercial & Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	107	762
Purchased Impaired | Commercial & Industrial | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,182	134
Purchased Impaired | Commercial & Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	2,870	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	13,693	13,707
Purchased Impaired | Residential 1-4 Family - Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	6,673	6,512
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	2,907	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	4,043	4,424
Purchased Impaired | Residential 1-4 Family - Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	70	0
Purchased Impaired | Residential 1-4 Family - Mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	17,180	16,766
Purchased Impaired | Residential 1-4 Family - Mortgage | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	10,701	9,894
Purchased Impaired | Residential 1-4 Family - Mortgage | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,614	1,030
Purchased Impaired | Residential 1-4 Family - Mortgage | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	4,865	5,842
Purchased Impaired | Residential 1-4 Family - Mortgage | 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	4	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	3	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	5,138	5,115
Purchased Impaired | HELOC | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	3,395	3,438
Purchased Impaired | HELOC | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	1,192	1,031
Purchased Impaired | HELOC | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	551	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	693	32
Purchased Impaired | Consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	681	17
Purchased Impaired | Consumer | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	0	0
Purchased Impaired | Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	12	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	686	717
Purchased Impaired | Other Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	55	57
Purchased Impaired | Other Commercial | Watch & Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans held for investment, net of deferred fees and costs	631	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