FAIR VALUE MEASUREMENT - Fair Value, Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Carrying Amount
Financial Assets
Cash and cash equivalents	$ 120,719	$ 198,692
Investment Securities:
Held to maturity, at carrying value	3,083	413,632
Mortgage-backed securities:
Held to maturity, at carrying value	159,848	495,874
FHLB stock, at cost	32,583	55,729
Equity investments	6,302	5,821
Loans, net of allowance for loan losses	3,285,780	3,273,575
Loans held for sale	601	2,001
Financial Liabilities:
Deposits	4,425,030	4,515,447
Federal funds purchased and repurchase agreements	36,810	9,498
FHLB borrowings	719,065	1,017,361
Subordinated notes, net of unamortized debt issuance costs	98,407	98,248
Trust preferred subordinated debentures, net of unamortized debt issuance costs	60,246	60,241
Estimated Fair Value
Financial Assets
Cash and cash equivalents	120,719	198,692
Investment Securities:
Held to maturity, at carrying value	3,046	421,928
Mortgage-backed securities:
Held to maturity, at carrying value	156,735	499,872
FHLB stock, at cost	32,583	55,729
Equity investments	6,302	5,821
Loans, net of allowance for loan losses	3,251,923	3,269,316
Loans held for sale	601	2,001
Financial Liabilities:
Deposits	4,417,902	4,506,133
Federal funds purchased and repurchase agreements	36,810	9,498
FHLB borrowings	708,904	1,008,292
Subordinated notes, net of unamortized debt issuance costs	97,611	99,665
Trust preferred subordinated debentures, net of unamortized debt issuance costs	54,729	47,622
Estimated Fair Value | Level 1
Financial Assets
Cash and cash equivalents	120,719	198,692
Investment Securities:
Held to maturity, at carrying value	0	0
Mortgage-backed securities:
Held to maturity, at carrying value	0	0
FHLB stock, at cost	0	0
Equity investments	0	0
Loans, net of allowance for loan losses	0	0
Loans held for sale	0	0
Financial Liabilities:
Deposits	0	0
Federal funds purchased and repurchase agreements	0	0
FHLB borrowings	0	0
Subordinated notes, net of unamortized debt issuance costs	0	0
Trust preferred subordinated debentures, net of unamortized debt issuance costs	0	0
Estimated Fair Value | Level 2
Financial Assets
Cash and cash equivalents	0	0
Investment Securities:
Held to maturity, at carrying value	3,046	421,928
Mortgage-backed securities:
Held to maturity, at carrying value	156,735	499,872
FHLB stock, at cost	32,583	55,729
Equity investments	6,302	5,821
Loans, net of allowance for loan losses	0	0
Loans held for sale	601	2,001
Financial Liabilities:
Deposits	4,417,902	4,506,133
Federal funds purchased and repurchase agreements	36,810	9,498
FHLB borrowings	708,904	1,008,292
Subordinated notes, net of unamortized debt issuance costs	97,611	99,665
Trust preferred subordinated debentures, net of unamortized debt issuance costs	54,729	47,622
Estimated Fair Value | Level 3
Financial Assets
Cash and cash equivalents	0	0
Investment Securities:
Held to maturity, at carrying value	0	0
Mortgage-backed securities:
Held to maturity, at carrying value	0	0
FHLB stock, at cost	0	0
Equity investments	0	0
Loans, net of allowance for loan losses	3,251,923	3,269,316
Loans held for sale	0	0
Financial Liabilities:
Deposits	0	0
Federal funds purchased and repurchase agreements	0	0
FHLB borrowings	0	0
Subordinated notes, net of unamortized debt issuance costs	0	0
Trust preferred subordinated debentures, net of unamortized debt issuance costs	$ 0	$ 0