LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Stated at Face Amount, Net of Deferred Fees and Costs) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	$ 9,805,723	$ 7,141,552	$ 6,554,046
Loans receivable, deferred fees and costs	2,700	1,300
Construction and Land Development
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,249,196	948,791	770,287
Commercial Real Estate - Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,279,155	943,933	870,559
Commercial Real Estate - Non-Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	2,230,463	1,713,659	1,631,767
Multifamily Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	547,520	357,079	353,769
Commercial & Industrial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	1,125,733	612,023	576,567
Residential 1-4 Family - Commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	714,660	612,395	580,568
Residential 1-4 Family - Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	604,354	485,690	476,871
Auto
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	288,089	282,474	271,466
HELOC
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	642,084	537,521	$ 527,863
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	839,699	408,667
Other Commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans held for investment, net	$ 284,770	$ 239,320