Quarterly report pursuant to Section 13 or 15(d)

LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Receivables Related Risk Rating Including Purchased Impaired Loans) (Details)

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LOANS AND ALLOWANCE FOR LOAN LOSSES (Loans Receivables Related Risk Rating Including Purchased Impaired Loans) (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Mar. 31, 2017
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs $ 9,805,723 $ 7,141,552 $ 6,554,046
Construction and Land Development      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 1,249,196 948,791 770,287
Commercial Real Estate - Owner Occupied      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 1,279,155 943,933 870,559
Commercial Real Estate - Non-Owner Occupied      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 2,230,463 1,713,659 1,631,767
Multifamily Real Estate      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 547,520 357,079 353,769
Commercial & Industrial      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 1,125,733 612,023 576,567
Residential 1-4 Family - Commercial      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 714,660 612,395 580,568
Residential 1-4 Family - Mortgage      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 604,354 485,690 476,871
Auto      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 288,089 282,474 271,466
HELOC      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 642,084 537,521 527,863
Consumer and all other      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 1,124,469 647,987 494,329
Purchased Impaired      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 102,861 39,021 57,770
Purchased Impaired | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 23,142 19,017  
Purchased Impaired | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 48,128 13,881  
Purchased Impaired | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 31,172 5,435  
Purchased Impaired | Doubtful      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 419 688  
Purchased Impaired | Construction and Land Development      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 10,202 2,838 2,776
Purchased Impaired | Construction and Land Development | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 1,410 1,462  
Purchased Impaired | Construction and Land Development | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 6,498 1,260  
Purchased Impaired | Construction and Land Development | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 2,294 116  
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 25,826 14,790 18,199
Purchased Impaired | Commercial Real Estate - Owner Occupied | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 6,788 4,958  
Purchased Impaired | Commercial Real Estate - Owner Occupied | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 11,261 7,486  
Purchased Impaired | Commercial Real Estate - Owner Occupied | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 7,777 2,346  
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 19,594 6,610 16,725
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 3,065 3,920  
Purchased Impaired | Commercial Real Estate - Non-Owner Occupied | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 10,689 1,394  
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 5,840 1,296  
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 3,380 80 2,058
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 | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 81 80  
Purchased Impaired | Multifamily Real Estate | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 3,299 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 2,890 408 733
Purchased Impaired | Commercial & Industrial | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 1,707 85  
Purchased Impaired | Commercial & Industrial | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 842 123  
Purchased Impaired | Commercial & Industrial | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 341 200  
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 14,826 9,414 11,946
Purchased Impaired | Residential 1-4 Family - Commercial | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 5,771 5,234  
Purchased Impaired | Residential 1-4 Family - Commercial | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 5,746 2,877  
Purchased Impaired | Residential 1-4 Family - Commercial | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 3,309 1,303  
Purchased Impaired | Residential 1-4 Family - Commercial | 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 - Mortgage      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 20,517 3,733 3,964
Purchased Impaired | Residential 1-4 Family - Mortgage | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 2,712 2,764  
Purchased Impaired | Residential 1-4 Family - Mortgage | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 10,142 329  
Purchased Impaired | Residential 1-4 Family - Mortgage | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 7,455 71  
Purchased Impaired | Residential 1-4 Family - Mortgage | Doubtful      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 208 569  
Purchased Impaired | Auto      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 14 0 0
Purchased Impaired | Auto | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 0    
Purchased Impaired | Auto | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 14    
Purchased Impaired | Auto | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 0    
Purchased Impaired | Auto | Doubtful      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 0    
Purchased Impaired | HELOC      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 1,884 950 1,156
Purchased Impaired | HELOC | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 719 446  
Purchased Impaired | HELOC | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 362 291  
Purchased Impaired | HELOC | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 592 94  
Purchased Impaired | HELOC | Doubtful      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 211 119  
Purchased Impaired | Consumer and all other      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 3,728 198 $ 213
Purchased Impaired | Consumer and all other | Pass      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 970 148  
Purchased Impaired | Consumer and all other | Special Mention      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 2,493 41  
Purchased Impaired | Consumer and all other | Substandard      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs 265 9  
Purchased Impaired | Consumer and all other | Doubtful      
Financing Receivable, Recorded Investment [Line Items]      
Loans held for investment, net of deferred fees and costs $ 0 $ 0