FAIR VALUE - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 323,856	$ 316,455
FHLB stock	12,790	13,175
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	192,427	142,098
Available for sale securities	323,856	316,455
Loans held for investment, net of allowance	2,177,818	1,873,724
FHLB stock	12,790	13,175
Accrued interest receivable	7,993	9,007
Deposits	2,286,615	1,870,183
Accrued interest payable	521	285
Borrowed funds	207,569	285,569
Subordinated debentures	9,277	9,196
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	192,427	142,098
Available for sale securities	323,856	316,455
Loans held for investment, net of allowance	2,184,269	1,872,056
Accrued interest receivable	7,993	9,007
Deposits	2,284,709	1,868,429
Accrued interest payable	521	285
Borrowed funds	206,850	284,989
Subordinated debentures	9,277	9,196
Estimated Fair Value | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	192,427	142,098
Available for sale securities	0	0
Loans held for investment, net of allowance	0	0
Accrued interest receivable	1	3
Deposits	0	0
Accrued interest payable	0	0
Borrowed funds	0	0
Subordinated debentures	0	0
Estimated Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Available for sale securities	323,856	316,455
Loans held for investment, net of allowance	0	0
Accrued interest receivable	2,081	3,616
Deposits	2,284,709	1,868,429
Accrued interest payable	521	285
Borrowed funds	206,850	284,989
Subordinated debentures	9,277	9,196
Estimated Fair Value | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Available for sale securities	0	0
Loans held for investment, net of allowance	2,184,269	1,872,056
Accrued interest receivable	5,911	5,388
Deposits	0	0
Accrued interest payable	0	0
Borrowed funds	0	0
Subordinated debentures	$ 0	$ 0