LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Stated at Face Amount, Net of Deferred Fees and Costs) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	$ 11,952,310	$ 9,716,207
Loans receivable, deferred fees and costs	5,800	5,100
Construction and Land Development
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,326,679	1,194,821
Commercial Real Estate - Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,921,464	1,337,345
Commercial Real Estate - Non-Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	2,970,453	2,467,410
Multifamily Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	591,431	548,231
Commercial & Industrial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,866,625	1,317,135
Residential 1-4 Family - Commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	815,309	713,750
Residential 1-4 Family - Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	865,502	600,578
Auto
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	300,631	301,943
HELOC
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	672,087	613,383
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	397,491	379,694
Other Commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	$ 224,638	$ 241,917