LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Stated at Face Amount, Net of Deferred Fees and Costs) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	$ 12,306,997	$ 9,716,207
Loans receivable, deferred fees and costs	8,100	5,100
Construction and Land Development
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,201,149	1,194,821
Commercial Real Estate - Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,979,052	1,337,345
Commercial Real Estate - Non-Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	3,198,580	2,467,410
Multifamily Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	659,946	548,231
Commercial & Industrial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	2,058,133	1,317,135
Residential 1-4 Family - Commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	721,185	640,419
Residential 1-4 Family - Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	913,245	673,909
Auto
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	328,456	301,943
HELOC
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	660,963	613,383
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	386,848	379,694
Other Commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	$ 199,440	$ 241,917