LOANS - Maturities and Rate Sensitivity (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	$ 3,136,336	$ 3,190,485	$ 3,012,275
Fixed rate	641,800
Adjustable rate	2,494,536
Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	746,709
Fixed rate	146,451
Adjustable rate	600,258
Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,635,357
Fixed rate	399,363
Adjustable rate	1,235,994
Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	754,270
Fixed rate	95,986
Adjustable rate	658,284
Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,038,715	1,066,266
Commercial & industrial | Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	379,735
Commercial & industrial | Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	591,714
Commercial & industrial | Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	67,266
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	185,849	220,230
Mortgage warehouse | Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	60,153
Mortgage warehouse | Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	125,696
Mortgage warehouse | Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	0
Owner occupied commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	435,366	415,230
Owner occupied commercial real estate | Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	22,806
Owner occupied commercial real estate | Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	166,466
Owner occupied commercial real estate | Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	246,094
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,068,832	1,067,779
Commercial real estate | Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	222,084
Commercial real estate | Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	617,481
Commercial real estate | Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	229,267
Construction, land & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	148,732	164,952
Construction, land & land development | Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	43,196
Construction, land & land development | Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	80,257
Construction, land & land development | Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	25,279
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	242,529	238,580
Residential mortgage | Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	12,555
Residential mortgage | Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	51,659
Residential mortgage | Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	178,315
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	16,313	$ 17,448
Consumer and other | Due in One Year or Less
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	6,180
Consumer and other | Due After One Year Through Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	2,084
Consumer and other | Due After Five Years
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	$ 8,049