LOANS - Portfolio by Type and Class (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	$ 3,363,354	$ 3,190,485	$ 3,071,761
Total loans held for sale	7,627	7,156
Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	3,074,574	2,676,491	2,485,239
Total loans held for sale	7,627	7,156
Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	288,780	513,994	586,522
Total loans held for sale	0	0
Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,142,733	1,066,266
Commercial & industrial | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,114,467	1,002,797
Commercial & industrial | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	28,266	63,469	82,135
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	236,307	220,230
Mortgage warehouse | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	236,307	220,230
Mortgage warehouse | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	0	0
Owner occupied commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	435,667	415,230
Owner occupied commercial real estate | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	382,886	327,906	312,162
Owner occupied commercial real estate | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	52,781	87,324	96,236
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,133,427	1,067,779
Commercial real estate | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,013,927	823,361	806,327
Commercial real estate | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	119,500	244,418	262,415
Construction, land & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	153,257	164,952
Construction, land & land development | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	137,634	136,998	146,522
Construction, land & land development | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	15,623	27,954	47,334
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	249,046	238,580
Residential mortgage | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	177,168	149,021	138,095
Residential mortgage | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	71,878	89,559	96,994
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	12,917	17,448
Consumer and other | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	12,185	16,178	15,418
Consumer and other | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	$ 732	$ 1,270	$ 1,408