LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Stated at Face Amount, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	$ 12,768,841	$ 12,610,936
Construction and Land Development
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	1,318,252	1,250,924
Commercial Real Estate - Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	2,051,904	2,041,243
Commercial Real Estate - Non-Owner Occupied
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	3,328,012	3,286,098
Multifamily Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	679,390	633,743
Commercial and Industrial
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	2,177,932	2,114,033
Residential 1-4 Family - Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	721,800	724,337
Residential 1-4 Family - Consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	854,550	890,503
Residential 1-4 Family - Revolving
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	652,135	659,504
Auto
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	358,039	350,419
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	352,572	372,853
Other Commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment, net of deferred fees and costs	$ 274,255	$ 287,279