FAIR VALUE MEASUREMENTS - Fair Values and Carrying Amounts (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financial Assets
Securities available for sale, at fair value	$ 710,147	$ 717,242
Level 1
Financial Assets
Cash and cash equivalents	61,393	90,685
Securities available for sale, at fair value	0	0
FHLB stock	0	0
Net loans	0	0
Accrued interest receivable	0	0
Cash surrender value of bank-owned life insurance policies	0	0
Derivative assets	0	0
Financial Liabilities
Total deposits	0	0
Securities sold under agreements to repurchase	0	0
FHLB advances	0	0
Derivative liabilities	0	0
Level 1 | Senior subordinated
Financial Liabilities
Subordinated borrowings	0	0
Level 1 | Junior subordinated
Financial Liabilities
Subordinated borrowings	0	0
Level 2
Financial Assets
Cash and cash equivalents	0	0
Securities available for sale, at fair value	710,147	717,242
FHLB stock	38,712	38,105
Net loans	0	0
Accrued interest receivable	3,498	3,347
Cash surrender value of bank-owned life insurance policies	58,811	57,997
Derivative assets	1,944	669
Financial Liabilities
Total deposits	2,291,030	2,348,574
Securities sold under agreements to repurchase	34,709	40,680
FHLB advances	698,844	744,006
Derivative liabilities	0	0
Level 2 | Senior subordinated
Financial Liabilities
Subordinated borrowings	5,000	38,033
Level 2 | Junior subordinated
Financial Liabilities
Subordinated borrowings	36,781	3,782
Level 3
Financial Assets
Cash and cash equivalents	0	0
Securities available for sale, at fair value	0	0
FHLB stock	0	0
Net loans	2,406,857	2,433,557
Accrued interest receivable	0	0
Cash surrender value of bank-owned life insurance policies	0	0
Derivative assets	8	0
Financial Liabilities
Total deposits	0	0
Securities sold under agreements to repurchase	0	0
FHLB advances	0	0
Derivative liabilities	(699)	(222)
Level 3 | Senior subordinated
Financial Liabilities
Subordinated borrowings	0	0
Level 3 | Junior subordinated
Financial Liabilities
Subordinated borrowings	0	0
Carrying Amount
Financial Assets
Cash and cash equivalents	61,393	90,685
Securities available for sale, at fair value	710,147	717,242
FHLB stock	38,712	38,105
Net loans	2,471,976	2,473,288
Accrued interest receivable	3,498	3,347
Cash surrender value of bank-owned life insurance policies	58,811	57,997
Derivative assets	1,952	669
Financial Liabilities
Total deposits	2,374,721	2,352,085
Securities sold under agreements to repurchase	34,740	40,706
FHLB advances	701,184	745,982
Derivative liabilities	(699)	(222)
Carrying Amount | Senior subordinated
Financial Liabilities
Subordinated borrowings	5,000	38,033
Carrying Amount | Junior subordinated
Financial Liabilities
Subordinated borrowings	38,003	5,000
Total Fair Value
Financial Assets
Cash and cash equivalents	61,393	90,685
Securities available for sale, at fair value	710,147	717,242
FHLB stock	38,712	38,105
Net loans	2,406,857	2,433,557
Accrued interest receivable	3,498	3,347
Cash surrender value of bank-owned life insurance policies	58,811	57,997
Derivative assets	1,952	669
Financial Liabilities
Total deposits	2,291,030	2,348,574
Securities sold under agreements to repurchase	34,709	40,680
FHLB advances	698,844	744,006
Derivative liabilities	(699)	(222)
Total Fair Value | Senior subordinated
Financial Liabilities
Subordinated borrowings	5,000	38,033
Total Fair Value | Junior subordinated
Financial Liabilities
Subordinated borrowings	$ 36,781	$ 3,782