FAIR VALUE MEASUREMENTS - Carrying Amounts and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financial assets:
Cash and cash equivalents	$ 124,413	$ 111,918	$ 132,365	$ 100,780
Investment securities available for sale	990,613	689,132
Investment securities held to maturity	38,735	39,182
Loans held for sale	76,876	47,287
Loans, net	5,145,420	3,066,775
Federal Home Loan Bank stock	41,225	24,844
Derivative assets	824	996
Purchased accounts receivable	4,980	52,688
Accrued interest receivable	20,516	12,695
Financial liabilities:
Deposits	5,219,470	3,310,297
Short-term borrowings	764,600	375,500
Long-term debt	159,424	194,967
Derivative liabilities	4,162	4,376
Accrued interest payable	3,013	2,550
Quoted prices in active markets for identical assets (Level 1)
Financial assets:
Cash and cash equivalents, Fair Value	124,413	111,918
Investment securities available for sale	39,034	16,532
SBA loans held for investment	0	0
Loans held for sale, Fair Value	0	0
Loans, net, Fair Value	0	0
Federal Home Loan Bank stock, at cost	0	0
Derivative assets	0	0
Purchased accounts receivable, fair value	0	0
Accrued interest receivable, Fair Value	0	0
Financial liabilities:
Deposits, Fair Value	0	0
Short term borrowings, Fair Value	0	0
Long-term debt, Fair Value	0	0
Derivative liabilities	0	0
Accrued interest payable, Fair Value	0	0
Significant other observable inputs (Level 2)
Financial assets:
Cash and cash equivalents, Fair Value	0	0
Investment securities available for sale	939,889	665,872
SBA loans held for investment	39,460	40,500
Loans held for sale, Fair Value	76,876	47,287
Loans, net, Fair Value	23,664	23,664
Federal Home Loan Bank stock, at cost	41,225	24,844
Derivative assets	397	588
Purchased accounts receivable, fair value	0	52,688
Accrued interest receivable, Fair Value	20,516	12,695
Financial liabilities:
Deposits, Fair Value	5,215,071	3,310,306
Short term borrowings, Fair Value	0	0
Long-term debt, Fair Value	0	0
Derivative liabilities	4,162	4,376
Accrued interest payable, Fair Value	3,013	2,550
Significant unobservable inputs (Level 3)
Financial assets:
Cash and cash equivalents, Fair Value	0	0
Investment securities available for sale	11,690	6,728
SBA loans held for investment	0	0
Loans held for sale, Fair Value	0	0
Loans, net, Fair Value	5,123,192	3,068,797
Federal Home Loan Bank stock, at cost	0	0
Derivative assets	427	408
Purchased accounts receivable, fair value	4,980	0
Accrued interest receivable, Fair Value	0	0
Financial liabilities:
Deposits, Fair Value	0	0
Short term borrowings, Fair Value	764,600	375,500
Long-term debt, Fair Value	172,746	198,928
Derivative liabilities		0
Accrued interest payable, Fair Value	0	0
Estimate of Fair Value Measurement
Financial assets:
Cash and cash equivalents, Fair Value	124,413	111,918
Investment securities available for sale	990,613	689,132
SBA loans held for investment	39,460	40,500
Loans held for sale, Fair Value	76,876	47,287
Loans, net, Fair Value	5,146,856	3,092,461
Federal Home Loan Bank stock, at cost	41,225	24,844
Derivative assets	824	996
Purchased accounts receivable, fair value	4,980	52,688
Accrued interest receivable, Fair Value	20,516	12,695
Financial liabilities:
Deposits, Fair Value	5,215,071	3,310,306
Short term borrowings, Fair Value	764,600	375,500
Long-term debt, Fair Value	172,746	198,928
Derivative liabilities	4,162	4,376
Accrued interest payable, Fair Value	$ 3,013	$ 2,550